JP4846252B2 - Elastic member - Google Patents

Description

  The present invention is an elastic member that is crosslinked by irradiation with active energy rays, has low tensile stress relaxation and tensile permanent elongation, has elasticity and flexibility close to vulcanized rubber, and has low performance deterioration even under high temperature conditions. About.

  Thermoplastic elastomers do not require a vulcanization process and can be molded in the same way as thermoplastic resins. In recent years, such as automotive parts, home appliance parts, electric wire coverings, medical parts, building material parts, footwear, sundries, etc. Used in a wide range of fields. Also in the field of stretchable members, thermoplastic elastomers that have rubber elasticity at room temperature and are easily plasticized and melted by heating to be easily molded are used for sanitary members, medical members, belt members, and bands. Used for materials and miscellaneous goods.

  Among thermoplastic elastomers, styrene-based thermoplastic elastomers, which are styrene-conjugated diene block copolymers or their hydrogenated products, are excellent in flexibility, moldability, etc., and have a low specific gravity. In recent years, coupled with problems such as environmental pollution, it has come to be used in a wide range of fields as an alternative to vulcanized rubber and polyvinyl chloride.

For stretchable members using styrene-based elastomers, various proposals have been made so far for the purpose of further improving molding processability and stretchability. For example, (1) Polymer block A mainly composed of vinyl aromatic compounds A hydrogenated block copolymer comprising a hydrogenated block copolymer obtained by hydrogenating a block copolymer having at least two polymer blocks B mainly composed of a conjugated diene compound, and a polyolefin. And polyolefin have a specific mass ratio, and the average fiber system is composed of ultrafine fibers of 10 μm or less, and has excellent elongation characteristics (elongation, elongation recovery), strength (water pressure resistance), and weather resistance Moreover, a stretchable nonwoven fabric having a soft texture (see Patent Document 1); (2) a polymer blow mainly composed of a vinyl aromatic compound And at least two polymer blocks B composed mainly of conjugated diene compounds, and at least one polymer block B is at the end of the polymer chain, and the total number average molecular weight and A stretchable nonwoven fabric made of a thermoplastic fiber produced from a hydrogenated block copolymer having a vinyl aromatic compound in a specific range and excellent in stretch properties (see Patent Document 2); (3) (a) Thermoplastic polymers having polar functional groups such as polyamide resins and polyester resins, and (b) block copolymers comprising vinyl aromatic compound polymer blocks and conjugated diene compound polymer blocks and / or their hydrides. Or the block / graft copolymer having the copolymer as a trunk portion and the graft portion being a radical decay type polymer. Modified block copolymer and / or modified block / graft copolymer in which molecular units containing functional groups that bind to or interact with the plastic polymer (a) (for example, unit groups based on maleic anhydride) are bonded Stretch nonwoven fabric formed from thermoplastic polymer composition containing coalescence and having excellent stretch recovery, flexibility, weather resistance, etc. (see Patent Document 3); (4) Block comprising polyvinylarene hard block and polyolefin soft block Stretching properties not only at room temperature, but also around human body temperature, obtained by electron beam crosslinking of a film produced from a thermoplastic polymer composition comprising a copolymer, a thermoplastic resin such as polyolefin or polystyrene, and a process oil, Examples thereof include a film excellent in lotion resistance (see Patent Document 4).
In recent years, cases in which thermoplastic elastomers are used under high temperature conditions (for example, 70 ° C.) are increasing, and development of members capable of maintaining performance even under such high temperature conditions is desired.

JP-A-3-130448 JP-A-2-259151 JP-A-63-203857 Special table 2003-509563 gazette

  However, the stretchable members (stretchable nonwoven fabrics and films) described in Patent Documents 1 to 4 are not necessarily satisfactory in performance such as tensile stress relaxation rate and tensile permanent elongation under high temperature conditions (for example, 70 ° C.). Rather, there is room for improvement in these performances.

  Thus, the object of the present invention is to solve such problems, have small tensile stress relaxation and tensile permanent elongation, have elasticity close to that of vulcanized rubber, and reduce performance even under high temperature conditions (for example, 70 ° C.). It is to provide a few elastic members.

According to the present invention, the above object is
[1] Polymer block A mainly composed of an aromatic vinyl compound unit having 40% by mass or more of a structural unit (a) derived from alkylstyrene having an alkyl group having 1 to 8 carbon atoms bonded to a benzene ring, and a conjugate At least one type of addition polymerization block copolymer selected from a block copolymer having a polymer block B mainly composed of a diene unit, at least a polymer block A part being crosslinkable by active energy rays, and a hydrogenated product thereof An elastic member obtained by molding a thermoplastic polymer composition containing 94.9% by mass to 99.9% by mass of the union (I) and subsequently performing an active energy ray irradiation treatment ;
[2 ] The elastic member according to [1 ], wherein the structural unit (a) is a p-methylstyrene unit;
[ 3 ] This is achieved by providing the stretchable member according to [1] or [2] , which is in the form of a fiber, a film, a sheet, a strand, a strip or a non-woven fabric.

  ADVANTAGE OF THE INVENTION According to this invention, the elastic member excellent in the tensile stress relaxation rate, tensile permanent elongation, etc. in high temperature conditions (for example, 70 degreeC) can be provided. The stretchable member of the present invention can be in the form of fibers, films, sheets, strips, non-woven fabrics, etc. that do not contain substances that cause environmental pollution, and is particularly suitable for sanitary applications such as paper diapers and sanitary products. be able to.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is described in detail below.
The addition polymerization block copolymer (I) constituting the thermoplastic polymer composition used in the stretchable member of the present invention is derived from alkylstyrene having an alkyl group having 1 to 8 carbon atoms bonded to a benzene ring. It has a polymer block A mainly composed of an aromatic vinyl compound unit having a structural unit (a) of 1% by mass or more, and a polymer block B mainly composed of a conjugated diene unit, and at least the polymer block A part has an active energy. It is at least one addition polymerization block copolymer selected from a block copolymer crosslinkable by a wire and a hydrogenated product thereof.

  In the polymer block A, examples of the alkyl styrene from which the structural unit (a) is derived include, for example, o-alkyl styrene, m-alkyl styrene, p-alkyl styrene, 2, 4 whose alkyl group has 1 to 8 carbon atoms. -Dialkyl styrene, 3,5-dialkyl styrene, 2,4,6-trialkyl styrene, halogenated alkyl styrene in which one or more of the hydrogen atoms of the alkyl group in the aforementioned alkyl styrenes are substituted with halogen atoms And the like. More specifically, examples of the alkylstyrene for deriving the structural unit (a) include o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, 3,5-dimethylstyrene, 2 , 4,6-trimethylstyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene, 2,4-diethylstyrene, 3,5-diethylstyrene, 2,4,6-triethylstyrene, o-propylstyrene M-propyl styrene, p-propyl styrene, 2,4-dipropyl styrene, 3,5-dipropyl styrene, 2,4,6-tripropyl styrene, 2-methyl-4-ethyl styrene, 3-methyl- 5-ethylstyrene, o-chloromethylstyrene, m-chloromethylstyrene, p-chloromethylstyrene, 2,4- (Chloromethyl) styrene, 3,5-bis (chloromethyl) styrene, 2,4,6-tri (chloromethyl) styrene, o-dichloromethylstyrene, m-dichloromethylstyrene, p-dichloromethylstyrene, etc. Can be mentioned.

  The polymer block A can have a unit derived from one or more of the alkyl styrene and the halogenated alkyl styrene described above as the structural unit (a). Among these, as the structural unit (a), a p-methylstyrene unit is preferable from the viewpoint of excellent crosslinking reactivity and easy availability.

  Examples of aromatic vinyl compound units other than the structural unit (a) that the polymer block A may have include, for example, styrene, α-methylstyrene, β-methylstyrene, monofluorostyrene, difluorostyrene, monochlorostyrene, dichlorostyrene, Examples thereof include units derived from methoxystyrene, vinylnaphthalene, vinylanthracene, indene, acetonaphthylene, and the like. Among these, units derived from styrene and α-methylstyrene are preferable.

  In the addition polymerization block copolymer (I), the polymer block A corresponds to the hard segment of the thermoplastic elastomer, and the alkyl group bonded to the benzene ring in the structural unit (a) is statically irradiated by active energy rays. It has a role which introduce | transduces bridge | crosslinking into the hard segment which consists of polymer block A by an appropriate crosslinking reaction.

  The proportion of the structural unit (a) in the polymer block A is the mass of the polymer block A constituting the addition polymerization block copolymer (I) [the weight of the addition polymerization block copolymer (I) is 2 or more. 1% by mass or more, preferably 10% by mass or more, more preferably 40% by mass or more, and all units are structural units (a ). When the proportion of the structural unit (a) is less than 1% by mass, crosslinking is not sufficiently introduced into the polymer block A, and the resulting elastic member does not exhibit sufficient elasticity. The bonding form of the structural unit (a) and the other aromatic vinyl compound unit in the polymer block A may be any form such as random, block, and tapered.

  The content of the polymer block A in the addition polymerization block copolymer (I) is preferably in the range of 10 to 40% by mass. When the content is less than 10% by mass, sufficient crosslinking is not generated, and the stretchability of the resulting stretchable member tends to decrease. When the content is greater than 40% by weight, the stretchable member is flexible. Tend to decrease.

  The polymer block A may have a small amount of structural units composed of other polymerizable monomers as necessary, together with the aromatic vinyl compound unit containing the structural unit (a). In this case, the proportion of the structural units composed of other polymerizable monomers is the mass of the polymer block A constituting the addition polymerization block copolymer (I) [addition polymerization block copolymer (I) is 2 In the case of having at least one polymer block A, the total mass] is preferably 30% by mass or less, and more preferably 10% by mass or less. Examples of the other polymerizable monomer in that case include butadiene and isoprene.

  Further, the addition polymerization block copolymer (I) is an aromatic vinyl compound not containing the structural unit (a) in addition to the polymer block A comprising the aromatic vinyl compound unit containing the structural unit (a). You may have the polymer block which consists of a unit.

  On the other hand, examples of the conjugated diene for deriving the conjugated diene unit constituting the polymer block B in the addition polymerization block copolymer (I) include butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1 , 3-pentadiene, 1,3-hexadiene and the like. The polymer block B may be composed of only one type of units derived from these conjugated dienes or may be composed of two or more types. Among these, it is preferable to be composed of units derived from butadiene, isoprene or a mixture of butadiene and isoprene. The type and content of the microstructure of the polymer block B are not particularly limited. Further, when two or more kinds of conjugated dienes are used in combination, their bonding form can be random, block, tapered, or a combination of two or more thereof.

  The polymer block B may have a small amount of structural units composed of other polymerizable monomers as required, together with the conjugated diene unit. In that case, the ratio of the other polymerizable monomer is the mass of the polymer block B constituting the addition polymerization block copolymer (I) [the addition polymerization block copolymer (I) is a polymer having two or more weights. When the combined block B is included, the total mass] is preferably 30% by mass or less, and more preferably 10% by mass or less. Examples of the other polymerizable monomer in that case include styrene, α-methylstyrene, and the above-described alkylstyrene (preferably p-methylstyrene) constituting the structural unit (a).

  The polymer block B includes a polyisoprene block composed of isoprene units or a hydrogenated polyisoprene block in which part or all of carbon-carbon double bonds based on the isoprene units are hydrogenated; a polybutadiene block composed of butadiene units or the butadiene Hydrogenated polybutadiene block in which some or all of the carbon-carbon double bonds based on the unit are hydrogenated; or an isoprene-butadiene copolymer block composed of isoprene units and butadiene units; or a carbon based on the isoprene units and butadiene units. A hydrogenated isoprene / butadiene copolymer block in which some or all of the carbon double bonds are hydrogenated is preferable.

  As long as the polymer block A and the polymer block B are bonded to the addition polymerization block copolymer (I), the bonding type is not limited and is linear, branched, radial, or those Any of two or more combined forms may be used. Among them, it is preferable that the bond form of the polymer block A and the polymer block B is a straight chain, for example, when the polymer block A is represented by A and the polymer block B is represented by B. Further, a triblock copolymer represented by A-B-A, a tetrablock copolymer represented by A-B-A-B, a pentablock copolymer represented by A-B-A-B-A, etc. Can be mentioned. Among them, the triblock copolymer (ABA) is preferably used from the viewpoints of ease of production of the addition polymerization block copolymer (I) and flexibility.

  The number average molecular weight of the addition polymerization block copolymer (I) is not particularly limited, but is preferably in the range of 30000 to 1000000, more preferably in the range of 40000 to 300000. In addition, the number average molecular weight here means the number average molecular weight in terms of polystyrene determined by gel permeation chromatography (GPC).

  The addition polymerization block copolymer (I) can be produced, for example, by the following known anionic polymerization method. That is, using an alkyl lithium compound as an initiator, an alkyl styrene for deriving the structural unit (a) or an alkyl styrene for deriving the structural unit (a) in an organic solvent inert to the polymerization reaction such as n-hexane or cyclohexane. A block copolymer (that is, an unhydrogenated addition-polymerized block copolymer (I)) is formed by sequentially polymerizing a mixture of an aromatic vinyl compound and a conjugated diene.

  The obtained block copolymer is further hydrogenated as necessary. Such a hydrogenation reaction is carried out, for example, by using the block copolymer in a saturated hydrocarbon solvent such as cyclohexane, Raney nickel; a metal such as Pt, Pd, Ru, Rh, or Ni as a support such as carbon, alumina, or diatomaceous earth. A heterogeneous catalyst supported on a Ziegler catalyst comprising a combination of an organometallic compound composed of metals of Groups 9 and 10 such as nickel and cobalt and an organoaluminum compound or organolithium compound such as triethylaluminum and triisobutylaluminum A hydrogenation catalyst such as a metallocene catalyst comprising a combination of a bis (cyclopentadienyl) compound of a transition metal such as titanium, zirconium or hafnium and an organometallic compound comprising lithium, sodium, potassium, aluminum, zinc or magnesium; Usually in the presence The reaction can be carried out under conditions of a reaction temperature of 20 to 100 ° C. and a hydrogen pressure of 0.1 to 10 MPa, and a hydrogenated product of the block copolymer (that is, a hydrogenated addition polymerization block copolymer (I)) Can be obtained.

  The hydrogenation rate can be appropriately adjusted according to the physical properties required for the thermoplastic polymer composition used in the stretchable member of the present invention, but when heat resistance, weather resistance and ozone resistance are important, It is preferable that 70% or more of the carbon-carbon double bond based on the conjugated diene unit of the polymer block B constituting the addition polymerization block copolymer (I) is hydrogenated. % Or more is more preferable, and 95% or more is more preferable. The hydrogenation rate of the carbon-carbon double bond based on the conjugated diene unit of the polymer block B is determined by the polymer block before and after the hydrogenation reaction by measuring means such as iodine titration, infrared spectrophotometer, and nuclear magnetic resonance. The amount of carbon-carbon double bond in B can be measured and calculated from the measured value.

  A crosslinking assistant (II) can be added to the thermoplastic polymer composition used for the stretchable member of the present invention, if necessary, for the purpose of improving the molding processability and the crosslinking property. Examples of the crosslinking aid (II) that can be used include triallyl isocyanurate, triallyl cyanurate, N, N′-phenylenebismaleimide, ethylene glycol di (meth) acrylate, propanediol di (meth) acrylate, butanediol di ( Examples include meth) acrylate, hexanediol di (meth) acrylate, nonanediol di (meth) acrylate, trimethylolpropane di (meth) acrylate, and trimethylolpropane tri (meth) acrylate. These may be used alone or in combination of two or more. The content of the crosslinking aid (II) is preferably 10% by mass or less, more preferably in the range of 0.1 to 10% by mass with respect to the total amount of the thermoplastic polymer composition. . When the content of the crosslinking aid (II) is more than 10% by mass, the thermoplastic polymer composition is excessively crosslinked by irradiation with active energy rays, and the stretchability tends to decrease.

  The thermoplastic polymer composition used in the stretchable member of the present invention is photopolymerized together with the crosslinking aid (II) for the purpose of improving the crosslinkability, particularly when ultraviolet rays (UV) are used as the active energy rays described later. Initiator (III) is preferably added. Usable photopolymerization initiators (III) include, for example, benzophenone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, α-methylol benzoin, α-methylol benzoin methyl ether, α-methoxybenzoin methyl ether, benzoin phenyl Examples include ether and α-t-butylbenzoin. These photopolymerization initiators may be used alone or in combination of two or more. As content of photoinitiator (III), it is preferable to exist in the range of 0.05-5 mass% with respect to the whole quantity of this thermoplastic polymer composition. When the content of the photopolymerization initiator (III) is less than 0.05% by mass, the exposure sensitivity is low, and it tends to be difficult to form a sufficient crosslink even by irradiating with ultraviolet rays. When the amount is large, the transmittance of ultraviolet rays is lowered, and on the contrary, the exposure sensitivity is lowered, so that sufficient crosslinking is not easily formed.

The thermoplastic polymer composition used in the stretchable member of the present invention may be added with a thermoplastic resin (IV) as necessary for the purpose of improving mechanical properties such as strength and molding processability. Good. Examples of the thermoplastic resin (IV) include homopolymers such as high density polyethylene (HDPE), medium density polyethylene, low density polyethylene (LDPE), and polypropylene; ethylene-propylene copolymer, ethylene-1-butene copolymer Polymer, ethylene-1-hexene copolymer, ethylene-1-heptene copolymer, ethylene-1-octene copolymer, ethylene-4-methyl-1-pentene copolymer, ethylene-1-nonene copolymer Ethylene-α-olefin copolymers such as ethylene-1-decene copolymer; ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid copolymer Polymers such as polymers, ethylene-methacrylate copolymers and resins modified with maleic anhydride, etc. Olefin resins; polystyrene, poly α-methyl styrene, poly p-methyl styrene, acrylonitrile-styrene resin, acrylonitrile-butadiene-styrene resin, maleic anhydride-styrene resin, and other styrene resins; polyacrylate resin, polymethacrylic resin Acrylic resins such as acid ester copolymers; Polyphenylene ether resins; Polycarbonate resins; Polyvinyl chloride resins; Polyvinyl acetate resins; Polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polylactic acid, polycaprolactone, polyamides 6, polyamide 6,6, polyamide 6,10, polyamide 11, polyamide 12, polyamide 6,12, polyhexamethylenediamine terephthalamide, xylene group-containing polyamide, etc. An amide-based resin. All of these have a solubility parameter (Solubility Parameters of Polymers; hereinafter referred to as SP value) used as a measure of polymer compatibility within a range of 15 to 23 (MPa) ^1/2. . The SP value here is a value calculated from the cohesive energy constant G of atoms and atomic groups, the molecular weight M of the polymer structural unit, and the density ρ of the polymer by the formula: SP value = ρΣG / M. In addition, it is supposed that the polymers having close SP values are basically compatible.

  When the thermoplastic resin (IV) is added to the thermoplastic polymer composition used in the stretchable member of the present invention, the addition amount is 100 parts by mass with respect to 100 parts by mass of the addition polymerization block copolymer (I). It is preferable that it is below, and it is more preferable that it is 80 mass parts or less. When the content of the thermoplastic resin (IV) exceeds 100 parts by mass with respect to 100 parts by mass of the addition polymerization block copolymer (I), the elasticity of the resulting elastic member tends to be lowered.

  As the thermoplastic resin (IV), a polyolefin resin, an acrylic resin, a polystyrene resin, a polyphenylene ether resin, or a polycarbonate resin is used. These resins are used together with the addition polymerization block copolymer (I). This is preferable because it is excellent in compatibility and easily obtains a stretchable member having good stretchability regardless of kneading conditions. Among these, a polyolefin resin is more preferable in that a good stretchable member can be easily obtained without impairing the crosslinkability of the addition polymerization block copolymer (I).

  In the thermoplastic polymer composition used for the stretchable member of the present invention, an addition polymerization block copolymer (for the purpose of modification such as flexibility and fluidity within the range not impairing the gist of the present invention) Rubber / elastomer components other than I) such as natural rubber, synthetic polyisoprene rubber, liquid polyisoprene rubber and hydrogenated product thereof, polybutadiene rubber, liquid polybutadiene rubber and hydrogenated product thereof, styrene-butadiene rubber, chloroprene rubber, ethylene- Propylene rubber, acrylic rubber, polyisoprene isobutylene rubber, acrylonitrile-butadiene rubber, polystyrene-polyisoprene-polystyrene block copolymer, polystyrene-polybutadiene-polystyrene block copolymer, or styrene elastomers such as hydrogenated products thereof. It is possible to focus.

  A softening agent can be added to the thermoplastic polymer composition used for the stretchable member of the present invention, if necessary. Examples of softeners that can be used include petroleum-based softeners such as paraffinic, naphthenic, and aromatic process oils, and vegetable oil-based softeners such as paraffin, peanut oil, and rosin. These softeners can be used alone or in combination of two or more. When the softener is added, the amount added is not particularly limited as long as the gist of the present invention is not impaired, but is usually 200 parts by mass or less with respect to 100 parts by mass of the addition polymerization block copolymer (I), The amount is preferably 100 parts by mass or less.

  If necessary, a rubber reinforcing agent or a filler may be added to the thermoplastic polymer composition used for the stretchable member of the present invention as long as the gist of the present invention is not impaired. Examples of the rubber reinforcing agent or filler include talc, mica, kaolin, clay, alumina, silica, glass, glass hollow sphere, glass fiber, magnesium carbonate, calcium carbonate, magnesium hydroxide, aluminum hydroxide, magnesium oxide, and titanium oxide. , Iron oxide, zinc oxide, barium ferrite, strontium ferrite, carbon black, graphite, activated carbon, carbon hollow sphere, carbon fiber, silicon carbide, calcium silicate, calcium aluminate, calcium titanate, wood flour, starch, organic pigment, etc. Is mentioned.

  The thermoplastic polymer composition used for the stretchable member of the present invention is, for example, a thermal polymerization inhibitor, a heat stabilizer, a light stabilizer, an ultraviolet absorber, and an antihalation within the range not impairing the gist of the present invention. Agents, antioxidants, lubricants, colorants, antistatic agents, flame retardants, foaming agents, water repellents, waterproofing agents, tackifiers, fluorescent agents, antiblocking agents, metal deactivators, antibacterial agents, etc. These additives may be added. These may be used individually by 1 type and may be used in combination of 2 or more types. Examples of the thermal polymerization inhibitor include 2,6-di-t-butyl-p-cresol, p-methoxyphenol, pentaerythritol tetrakis [3- (3 ′, 5′-di-t-butyl-4′-hydroxy). Phenylpropionate], hydroquinone, t-butylcatechol, t-butylhydroxyanisole, 4,4′-butylidenebis (3-methyl-6-t-butyl) phenol, and the like.

  Components such as the above-mentioned addition polymerization block copolymer (I) and crosslinking aid (II), photopolymerization initiator (III), thermoplastic resin (IV), etc., which are added as necessary, are, for example, uniaxial extrusion The thermoplastic polymer composition used for the stretchable member of the present invention can be obtained by kneading using a kneader such as a machine, a twin screw extruder, a Banbury mixer, a brabender, an open roll, or a kneader. . In this case, the kneading temperature is generally preferably in the range of 120 to 280 ° C, more preferably in the range of 140 to 260 ° C.

  The stretchable member of the present invention can be produced by molding the thermoplastic polymer composition thus obtained and subsequently performing an active energy ray irradiation treatment. The stretchable member of the present invention can be made into a form suitable for each according to the application, such as a fiber, a film, a sheet, a strip, a strand, and a nonwoven fabric.

  In the present invention, the molding method for shaping the thermoplastic polymer composition into the various forms described above is not particularly limited, and a general molding method according to the form of each molded body can be employed.

  In the case of forming into a fiber shape, an apparatus substantially equivalent to an apparatus used when melt spinning an ordinary thermoplastic resin, for example, a type in which a gear pump is coupled to a screw extruder, etc., may be used. it can. By controlling the spinning temperature, spinning pressure, extrusion speed, spinning hole shape, and winding speed, the denier configuration of the produced fiber can be variously changed as in the case of ordinary melt spinning. In addition, when sticking occurs between the wound fibers, an aqueous surfactant solution or finely divided talc, calcium carbonate, titanium oxide, silica, alumina, etc. on the spun yarn before winding to prevent this. It is preferable to apply an aqueous solution in which is dispersed. The fiber wound in this way may be stretched as in the case of ordinary thermoplastic synthetic fibers, but may not be stretched, and steps such as heat treatment can be omitted. The thickness of the fiber can be arbitrarily selected within a range of several deniers as in the case of ordinary thermoplastic synthetic fibers. The cross-sectional shape of the fiber may be any of a flat cross-section, a polygonal cross-section, a multi-leaf cross-section, a hollow cross-section, etc. in addition to a normal round cross-section.

  When forming into the form of a film, a sheet, a strand or a strip, it can be formed using a single screw extruder or a twin screw extruder. The thickness and width of the film and sheet are not particularly limited, but usually the thickness is preferably in the range of 15 μm to 2 mm. Moreover, the cross-sectional shape of the strand is not particularly limited, and for example, a shape such as a circle, an ellipse, and a square is preferable. The thickness and width of the strip are not particularly limited, but usually the thickness is preferably in the range of 200 μm to 2 mm.

In the case of shaping into a nonwoven fabric, for example, a melt blown nonwoven fabric is formed by melt spinning a thermoplastic polymer composition using a normal melt blown nonwoven fabric manufacturing apparatus and forming a fiber web on the collection surface of the thermoplastic polymer composition. Can be manufactured. The nonwoven fabric can also be produced by a spunbond method in which a fiber web is formed in advance and then heated with a roll or the like to partially bond the fiber contacts. There is no restriction | limiting in particular in the fineness of the fiber which comprises a nonwoven fabric, a fabric weight, etc., It can make it suitable according to a use. In addition, it is preferable that the fiber which comprises this nonwoven fabric is a long fiber with uniform fineness from the point which is excellent in the tensile stress relaxation rate after irradiation bridge | crosslinking, and a tensile permanent elongation. Further, the basis weight of the nonwoven fabric is preferably in the range of 5 to 200 g / m ² from the viewpoint of handleability.

  The molding temperature when shaping the thermoplastic polymer composition used in the stretchable member of the present invention into the various forms described above is generally preferably in the range of 120 to 280 ° C, and preferably in the range of 140 to 260 ° C. More preferred.

  The molded body thus obtained is subjected to an active energy ray irradiation treatment to crosslink at least the polymer block A portion of the addition polymerization block copolymer (I) to produce the stretchable member of the present invention. be able to.

  Examples of the active energy rays include particle rays, electromagnetic waves, and combinations thereof. Examples of the particle beam include electron beams (EB) and α rays, and examples of the electromagnetic waves include ultraviolet rays (UV), visible rays, infrared rays, γ rays, and X rays. Among these, an electron beam and an ultraviolet ray are preferable, and when the thermoplastic polymer composition in the present invention contains a crosslinking aid (II), an electron beam is more preferred, and photopolymerization is initiated with the crosslinking aid (II). When the agent (III) is contained, ultraviolet rays are more preferable. These active energy rays can be irradiated using a known apparatus. In the case of an electron beam, an acceleration voltage of 0.1 to 10 MeV and an irradiation dose of 1 to 500 kGy are appropriate. In the case of ultraviolet rays, a lamp having a radiation wavelength of 200 nm to 450 nm can be suitably used as the radiation source. Examples of the radiation source include a tungsten filament in the case of an electron beam, and examples include a low-pressure mercury lamp, a high-pressure mercury lamp, an ultraviolet mercury lamp, a carbon arc lamp, a xenon lamp, and a zirconium lamp.

  In the thermoplastic polymer composition used for the stretchable member of the present invention, active energy rays are irradiated to crosslink at least the polymer block A portion of the addition polymerization block copolymer (I) as a constituent component. In addition to the polymer block A part, the polymer block B part of the addition polymerization type block copolymer (I) and the thermoplastic resin (IV) may be partially crosslinked. However, it does not inhibit the object of the present invention.

  The elastic member of the present invention has a tensile stress relaxation rate of 30% or less when held for 100 minutes at 40 ° C. and 50% elongation in a stress relaxation test described in JIS K 6263 as a measure of excellent stretchability. Alternatively, the tensile stress relaxation rate is preferably 50% or less when held at 70 ° C. and 50% elongation for 10 minutes. When this condition is satisfied, the object of the present invention can be achieved more effectively.

  EXAMPLES Hereinafter, although an Example etc. demonstrate this invention further more concretely, this invention is not limited at all by these Examples. In the following examples and comparative examples, the physical properties of the obtained elastic members were evaluated by the following methods.

1) Toluene extraction rate 30 ml of toluene in a 50 ml screw tube, into which a part of a strip-shaped No. 2 test piece used for measurement of the tensile stress relaxation rate described later was cut, and the test piece was precisely weighed in advance (About 0.3 g) was added. After shaking for 12 hours at 25 ° C. using a shaker, the test piece was taken out and dried under reduced pressure at 100 ° C. for 180 minutes, and the mass was measured. From the obtained value, the toluene extraction rate was calculated according to the following formula, and the result was used as an index of crosslinkability.
Toluene extraction rate (%) = 100 × (A ₀ −A ₁ ) / A ₀
However, _A0 : Mass (g) of the test piece before a test
A ₁ : Mass of the test piece after the test (g)

2) Tensile stress relaxation rate Measured according to the method described in JIS K 6263. That is, a strip-shaped test piece No. 2 was punched out from the polymer composition sheets obtained in Examples and Comparative Examples, and the distance between the grippers was measured using an Instron universal testing machine under preset measurement conditions. After measuring the initial tensile stress (m ₀ ) when stretched by 50% at a test speed of 300 mm / min at 20 mm, the tensile stress (m ₁ ) after being held for a certain period of time in the same state is measured. Thus, the tensile stress relaxation rate was obtained. The measurement was performed under two conditions: [1] holding at an ambient temperature of 40 ° C. for 100 minutes, and [2] holding at an atmospheric temperature of 70 ° C. for 10 minutes.
Tensile stress relaxation rate (%) = 100 × (m ₀ -m ₁ ) / m ₀

3) Tensile permanent elongation It measured according to the method described in JIS K 6262. That is, a strip-shaped test piece No. 2 was punched out from the sheet of the polymer composition obtained in the examples and comparative examples, and a 2 cm wide marked line was attached to the test piece, and the atmosphere temperature was 25 ° C. or 50 ° C. at 70 ° C. Elongated, held for 2 hours, then opened, and after 30 minutes, the length between the marked lines (L ₁ (cm)) was measured, and the tensile permanent elongation was determined by the following formula.
Tensile permanent elongation (%) = 100 × (L ₁ -2) / 2

4) Hardness Measured according to the method described in JIS K 6253. That is, three sheets of the polymer composition obtained in the examples and comparative examples were stacked and measured using an ASTM A hardness meter, and used as an index of flexibility.

  The block copolymers used in the following Examples and Comparative Examples were those obtained in Reference Examples 1 to 3.

Reference example 1
In a pressure-resistant vessel equipped with a stirrer, 40 kg of cyclohexane and 200 ml of sec-butyllithium (11% by mass, cyclohexane solution) are added. Next, after adding 100 g of tetrahydrofuran, 13 kg of butadiene is added over 60 minutes and polymerized at 50 ° C. for 60 minutes, and further 1.43 kg of p-methylstyrene is added over 30 minutes and polymerized at 50 ° C. for 60 minutes. As a result, a reaction mixture liquid containing poly-p-methylstyrene-polybutadiene-poly-p-methylstyrene triblock copolymer was obtained. The number average molecular weight of the obtained block copolymer was 105000, and the p-methylstyrene content measured by ¹ H-NMR was 22% by mass.
A hydrogenation catalyst prepared separately by adding 350 g of triisopropylaluminum (20% by mass, cyclohexane solution) to 60 g of nickel octylate (64% by mass, cyclohexane solution) is added to the reaction mixture containing the block copolymer, A hydrogenation reaction is carried out in a hydrogen atmosphere at 80 ° C. and 1 MPa, and a hydrogenated product of the above-mentioned poly p-methylstyrene-polybutadiene-poly p-methylstyrene triblock copolymer (hereinafter referred to as a block copolymer (I -1)). The number average molecular weight of the obtained block copolymer (I-1) was 110000, and the p-methylstyrene content and the hydrogenation rate measured by ¹ H-NMR were 21% by mass and 98%, respectively. .

Reference example 2
In a pressure vessel equipped with a stirrer, 40 kg of cyclohexane and 240 ml of sec-butyllithium (11% by mass, cyclohexane solution) are added, and a mixed solution of p-methylstyrene and styrene (p-methylstyrene / styrene = 50/50) is added to this solution. (Mass ratio)) 1.17 kg was added over 30 minutes and polymerized at 50 ° C. for 60 minutes, then 80 g of tetrahydrofuran was added, and then 10.7 kg of butadiene was added over 60 minutes and polymerized at 50 ° C. for 60 minutes. Further, 1.17 kg of a mixed liquid of p-methylstyrene and styrene (p-methylstyrene / styrene = 50/50 (mass ratio)) was added over 30 minutes and polymerized at 50 ° C. for 60 minutes to obtain poly p- Reaction mixing comprising methylstyrene / styrene-polybutadiene-poly p-methylstyrene / styrene triblock copolymer It was obtained. The number average molecular weight of the obtained block copolymer was 89000, and the combined content of p-methylstyrene and styrene measured by ¹ H-NMR was 18% by mass.
A hydrogenation catalyst prepared separately by adding 350 g of triisopropylaluminum (20% by mass, cyclohexane solution) to 60 g of nickel octylate (64% by mass, cyclohexane solution) is added to the reaction mixture containing the block copolymer, A hydrogenation reaction was performed in a hydrogen atmosphere at 80 ° C. and 1 MPa, and a hydrogenated product of the poly (p-methylstyrene / styrene) -polybutadiene-poly (p-methylstyrene / styrene) triblock copolymer described above (hereinafter, This was referred to as a block copolymer (I-2). The number average molecular weight of the obtained block copolymer (I-2) was 90000, and was measured by ¹ H-NMR. The p-methylstyrene / styrene content and the hydrogenation rate were 17% by mass and 98%, respectively.

Reference example 3
In a pressure-resistant vessel equipped with a stirrer, 40 kg of cyclohexane and 240 ml of sec-butyllithium (11% by mass, cyclohexane solution) are added, and 1.17 kg of styrene is added to this solution over 30 minutes, followed by polymerization at 50 ° C. for 30 minutes. After adding 80 g of tetrahydrofuran to 10.7 kg of butadiene over 60 minutes and polymerizing at 50 ° C. for 60 minutes, further adding 1.17 kg of styrene over 30 minutes and polymerizing at 50 ° C. for 30 minutes, polystyrene was obtained. A reaction mixture containing a polybutadiene-polystyrene triblock copolymer was obtained. The number average molecular weight of the obtained block copolymer was 89000, and the styrene content measured by ¹ H-NMR was 18% by mass.
A hydrogenation catalyst prepared separately by adding 350 g of triisopropylaluminum (20% by mass, cyclohexane solution) to 60 g of nickel octylate (64% by mass, cyclohexane solution) is added to the reaction mixture containing the block copolymer, A hydrogenation reaction was performed in a hydrogen atmosphere at 80 ° C. and 1 MPa to obtain a hydrogenated product of the above-described polystyrene-polybutadiene-polystyrene triblock copolymer (hereinafter referred to as a block copolymer (1)). The number average molecular weight of the obtained block copolymer (1) was 90000, and was measured by ¹ H-NMR. The styrene content and the hydrogenation rate were 17% by mass and 98%, respectively.

The contents of the crosslinking aid (II), photopolymerization initiator (III) and thermoplastic resin (IV) used in the following examples or comparative examples are as follows.
○ Crosslinking aid (II-1) :
Triallyl isocyanurate [Nippon Kasei Co., Ltd. “Tyke WH-60” (trade name)]
○ Crosslinking aid (II-2) :
Hexanediol diacrylate [Shin-Nakamura Chemical Co., Ltd. “NK-ESTER A-HD-N” (trade name)]
○ Photopolymerization initiator (III-1) :
α-methylol benzoin methyl ether [“Irgacure 651” (trade name) manufactured by Ciba Specialty Chemicals]
○ Resin (IV-1) :
Low-density polyethylene [Novatec LD LC500 manufactured by Nippon Polyethylene Co., Ltd. (trade name) MFR (190 ° C., 2.16 kg load) = 4 g / 10 min]

<Examples 1-5>
Block copolymer (I-1), block copolymer (I-2), crosslinking aid (II-1), thermoplastic resin (IV-1) and antioxidant obtained in Reference Examples 1 and 2 Were melt kneaded at 180 ° C. in a twin-screw extruder at the ratio shown in Table 1 (all parts by mass) to obtain a thermoplastic polymer composition. A sheet having a length of 15 cm, a width of 15 cm, and a thickness of 0.1 cm was produced from the obtained thermoplastic polymer composition by press molding (molding temperature: 180 ° C., press pressure: 10 MPa, press time: 1 minute). The lines were irradiated at an acceleration voltage of 5.0 MeV and at the doses shown in Table 1. Using the sheet-like stretchable member thus obtained, the various performances described above were evaluated. The results are shown in Table 1.

<Comparative Examples 1-5>
Block copolymer (I-1), block copolymer (1), crosslinking aid (II-1), thermoplastic resin (IV-1) and antioxidant obtained in Reference Examples 1 and 3 Were melt kneaded at 180 ° C. in a twin-screw extruder at the ratio shown in Table 2 (all parts by mass) to obtain a thermoplastic polymer composition. A sheet having a length of 15 cm, a width of 15 cm, and a thickness of 0.1 cm was produced from the obtained thermoplastic polymer composition by press molding (molding temperature: 180 ° C., press pressure: 10 MPa, press time: 1 minute). The lines were irradiated at an acceleration voltage of 5.0 MeV and at the doses shown in Table 2. Using the sheet-like member thus obtained, the various performances described above were evaluated. The results are shown in Table 2.

  From the results shown in Table 1 and Table 2, in the elastic members obtained in Examples 1 to 5, the tensile stress relaxation rate at 40 ° C. and high temperature (70 ° C.), the tensile at 25 ° C. and high temperature (70 ° C.) It turns out that permanent elongation is small compared with the member obtained by Comparative Examples 1-5, and has the outstanding elasticity.

<Examples 6-9, Comparative Examples 6-7>
Block copolymer (I-1), block copolymer (I-2), block copolymer (1), crosslinking aid (II-2), photopolymerization initiator obtained in Reference Examples 1 to 3 A thermoplastic polymer composition obtained by melt-kneading (III-1), the thermoplastic resin (IV-1) and the antioxidant in the proportions shown in Table 3 (all parts by mass) at 170 ° C. in a twin-screw extruder. Got. A sheet having a length of 15 cm, a width of 15 cm, and a thickness of 0.1 cm was produced from the obtained thermoplastic polymer composition by press molding (a molding temperature of 170 ° C., a press pressure of 10 MPa, and a press time of 1 minute), and then ultraviolet rays were applied to both sides. (UV) was irradiated at 500 mJ / cm ² . Using the sheet-like stretchable member thus obtained, the various performances described above were evaluated. The results are shown in Table 3.

  From the results shown in Table 3, in the elastic members obtained in Examples 6 to 9, the tensile stress relaxation rate at 40 ° C. and high temperature (70 ° C.), and the tensile permanent elongation at 25 ° C. and high temperature (70 ° C.). It turns out that it is small compared with the member obtained by Comparative Examples 6-7, and has the outstanding elasticity.

Since the stretchable member of the present invention has excellent stretchability, taking advantage of its features, for example, sanitary uses such as disposable diapers, toilet training pants, sanitary goods, underwear; base materials for poultices, stretchable tapes, It can be effectively used for a wide range of medical uses such as bandages, surgical clothes, supporters, corrective clothes, etc .; band uses such as hair bands, wristbands, watch bands, and eyeglass bands; and miscellaneous goods such as rubber bands and training tubes.

Claims (3)

A polymer block A mainly composed of an aromatic vinyl compound unit having a structural unit (a) derived from alkylstyrene having an alkyl group having 1 to 8 carbon atoms bonded to a benzene ring, and a conjugated diene unit; At least one type of addition polymerization block copolymer (I) selected from a block copolymer having a polymer block B as a main component and at least a polymer block A portion being crosslinkable by active energy rays and a hydrogenated product thereof ) Is a stretchable member obtained by molding a thermoplastic polymer composition containing 94.9% by mass to 99.9% by mass , followed by active energy ray irradiation treatment. The elastic unit according to claim 1, wherein the structural unit (a) is a p-methylstyrene unit. The stretchable member according to claim 1 or 2 , which is in the form of a fiber, a film, a sheet, a strand, a strip or a non-woven fabric.