JP2004250680A - Styrene-based resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve surface impact strength of a molded product of an impact resistant styrene-based resin composition and improve the balance between the surface impact strength and rigidity. <P>SOLUTION: The styrene-based resin composition comprises a styrene-based copolymer (A) and a block copolymer (B) consisting of a polymer block (b1) of a styrene-based monomer and a polymer block (b2) of a conjugated diene-based monomer. The styrene-based copolymer (A) is a copolymer comprising a styrene-based monomer (a), butyl acrylate (b) and methyl methacrylate (c). The block copolymer (B) forms a multilayer structure in which the polymer block (b1) and the polymer block (b2) are alternately laminated [the black part in the figure indicates the block copolymer (B)], and contains 9-25 mass% structural unit based on the conjugated diene-based monomer in the styrene-based resin composition in the raw material mass ratio. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a novel styrene resin composition obtained by mixing a styrene resin and a thermoplastic elastomer.

  Styrene resins are widely used in plastic containers because of their excellent moldability. In recent years, in the field of plastic containers, the replacement of vinyl chloride-based resins with styrene-based resins has been progressing due to environmental load and other problems. A so-called impact-resistant styrene-based resin composition in which a thermoplastic elastomer is blended with a base resin is frequently used. However, when the proportion of the thermoplastic elastomer is increased, the impact-resistant styrenic resin composition improves the impact resistance, but reduces the rigidity of the molding sheet and causes a molded article due to external load. Are easily deformed, so that in the case of a container for packing the contents, the contents are easily damaged. On the other hand, when the amount of the thermoplastic elastomer in the impact-resistant styrenic resin composition is reduced, the rigidity of the molded product is increased, but the impact strength is reduced and the molded product is liable to crack, break or crack. Was. Therefore, conventionally, studies have been made to balance the rigidity and the impact resistance of such mutually contradictory molded products. For example, a styrene-butadiene block copolymer having a styrene block amount of 65 to 85% by mass, There is known a transparent impact-resistant resin composition containing a styrene-butyl acrylate copolymer and a styrene-butadiene block copolymer having a styrene block amount of 10 to 50% by mass (for example, see Patent Document 1 below). ).

  However, although the transparent impact-resistant resin composition can have both rigidity and impact resistance in a molded product of the composition, the surface impact strength when molded is still insufficient. In particular, in the case of various secondary molded products such as blister packages, carrier tapes, food containers, etc. obtained by secondary molding of molding sheets, cracks and cracks occur due to vibration during dropping and transportation while the contents are packed It was easy.

JP-A-7-309992

  The problem to be solved by the present invention is to dramatically improve the surface impact strength of a molded article of the impact-resistant styrene resin composition, and to improve the balance between the surface impact strength and the rigidity.

  The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that the styrene-based copolymer (A), the polymer block (b1) of the styrene-based monomer, and the conjugated diene-based monomer A styrene-based resin composition comprising a block copolymer (B) composed of a polymer block (b2), wherein the styrene-based copolymer (A) is a styrene-based monomer (a), acrylic acid A terpolymer of butyl (b) and methyl methacrylate (c), wherein the block copolymer (B) has a predetermined morphology in the composition, and the conjugated diene monomer When the structural unit derived from the body is 9 to 25% by mass in the styrenic resin composition in terms of the raw material mass ratio, the molded product exhibits excellent rigidity and the surface impact strength is dramatically improved. Have led to the completion of the present invention. .

That is, the present invention provides a styrene-based copolymer (A), a styrene-based monomer polymer block (b1), and a conjugated diene-based polymer block (b2). A) a styrenic resin composition comprising:
The styrene-based copolymer (A) is a copolymer of a styrene-based monomer (a), butyl acrylate (b) and methyl methacrylate (c),
The block copolymer (B) has a multilayer structure in which layers of the polymer block (b1) and layers of the polymer block (b2) of diene-based monomers are alternately laminated; and
A styrene-based resin composition, comprising a structural unit derived from the conjugated diene-based monomer in a raw material mass ratio of 9 to 25% by mass in the styrene-based resin composition.

  The present invention further relates to a molding sheet comprising the styrene resin composition.

  The present invention further relates to a blister package comprising the styrene resin composition.

  As described above, the transparent styrene-based resin composition of the present invention comprises a styrene-based copolymer (A), a styrene-based polymer block (b1), and a conjugated diene-based monomer block ( b2), and the styrene-based copolymer (A) is a styrene-based monomer (a), butyl acrylate (b), and methyl methacrylate. (C). The block copolymer (B) comprises a layer of a styrene monomer polymer block (b1) in the block copolymer (B) and a conjugated diene monomer polymer block (b2). ) Are alternately laminated to form a multilayer structure, and the styrene-based copolymer (A) penetrates into the layers of the multilayer structure to form a continuous layer. Here, the morphology in which the styrene-based copolymer (A) forms a continuous layer and the block copolymer (B) forms a multilayer structure is specifically shown in a transmission electron micrograph shown in FIG. (TEM). In FIG. 1, the black portion corresponds to the layer of the polymer block (b2) of the conjugated diene monomer in the block copolymer (B), and the white portion surrounded by this layer is styrene. This corresponds to the layer of the polymer block (b1) of the system monomer.

  The block copolymer (B) composed of the styrene monomer polymer block (b1) and the conjugated diene monomer polymer block (b2) is itself a block copolymer (B). ) Has a multilayer structure in which layers of the polymer block (b1) and layers of the polymer block (b2) of the conjugated diene monomer are alternately laminated. In the present invention, the styrene-based copolymer (A) is present as a continuous layer between layers of the polymer block (b2) of a plurality of conjugated diene-based monomers without breaking the multilayer structure as much as possible. The impact strength was improved. On the other hand, in the case of the above-mentioned prior art in which SBS is used as a block copolymer and a binary copolymer of a styrene monomer and butyl acrylate is used as a continuous layer, the copolymer and the block copolymer are used. Since the polymer is easily compatible with the polymer, the morphology of the SBS is destroyed, and the surface impact strength of the above-mentioned molded product, particularly the surface impact strength of the molded product obtained by secondary molding of the molding sheet, does not reach a sufficient level. Was something.

  In the present invention, in particular, methyl methacrylate (c) was used as a monomer component of the styrene-based copolymer (A) forming the continuous layer, and the structural unit derived from the conjugated diene-based monomer was used as a raw material mass. By setting the ratio to 9 to 25% by mass in the styrene-based resin composition on a ratio basis, the above-described appropriate morphology can be developed and the balance between surface impact strength and rigidity can be achieved. Here, the structural unit derived from the conjugated diene-based monomer means an alkylene structure site obtained by the addition reaction of the conjugated diene-based monomer. For example, 1,3-butadiene is used as a conjugated diene-based monomer. When used, they represent but-2-ene-1,4-diyl and but-3-en-1,2-diyl.

  Further, in order to form such an appropriate morphology, a ratio of the structural unit derived from methyl methacrylate (c) in the styrene resin composition to be 1.5 to 6% by mass based on the mass ratio of the raw materials. Is preferable. Here, the structural unit derived from methyl methacrylate (c) refers to a structural site where the methyl methacrylate (c) has undergone an addition reaction, specifically, 1-methyl-1-methyloxycarbonyl-ethylene.

  Furthermore, the abundance of structural units derived from butyl acrylate (b) also affects the morphology formation of the styrenic resin composition, and as this increases, the proportion of the multilayer structure tends to decrease. On the other hand, as the number of the structural units decreases, the ratio of the multilayer structure tends to increase, but the rigidity decreases. Therefore, from these points, it is preferable that the ratio of the structural unit derived from butyl acrylate (b) be 2.8 to 8.5% by mass in the styrene resin composition based on the mass ratio of the raw materials. Here, the structural unit derived from butyl acrylate (b) refers to a structural site where the butyl acrylate (b) has undergone an addition reaction, specifically, 1-butyloxycarbonyl-ethylene.

Here, the content of the structural unit derived from the conjugated diene monomer, the structural unit derived from methyl methacrylate (c), and the structural unit derived from butyl acrylate (b) in the styrene-based resin composition is as follows: It can be determined from the area ratio of chemical peaks corresponding to carbon atoms characteristic of each structural unit in C ¹³ -NMR measurement. For example, in the case of the structural unit derived from methyl methacrylate (b), the chemical shift of the carbonyl carbon atom is 175 ppm, and in the case of the structural unit derived from butyl acrylate (b), the chemical unit of the carbon atom of the butyl group bonded to the oxygen atom is used. The content of these structural units can be determined from the area ratio of the peak at a shift of 63 ppm.

  As described above, the styrene-based copolymer (A) that forms the continuous layer in the transparent styrene-based resin composition of the present invention includes a styrene-based monomer (a), butyl acrylate (b), and methyl methacrylate. It is a copolymer of (c). By using butyl acrylate (b) as a copolymer component of the styrene monomer (a), the composition itself can be imparted with flexibility, and using methyl methacrylate (c). Thus, the compatibility with the styrene-butadiene block copolymer (B) can be suppressed, and the morphology of the block copolymer (B) can be maintained.

  Here, the styrene monomer constituting the styrene copolymer (A) is styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, ethylstyrene, isobutylstyrene, t -Butylstyrene, o-bromostyrene, m-bromostyrene, p-bromostyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene and the like. Of these, styrene is preferred because of its good reactivity and easy polymerization.

The styrene-based copolymer (A) contains 78 to 85% by weight of a styrene-based monomer (a), 6 to 19% by weight of butyl acrylate (b), and 3 to 16% by weight of methyl methacrylate (c). % Of the copolymer. As described later, the content of the polybutadiene block in the block copolymer (B) is preferably 20 to 30% by mass from the viewpoint of the surface impact strength of the molded product, and the styrene copolymer is preferably used. By setting the raw material monomer ratio of the polymer (A) to the above-mentioned ratio of 78 to 85% by mass, excellent transparency can be imparted to the molded product. Furthermore, the balance between surface impact strength and rigidity is further improved. In particular, from the viewpoint of the transparency of the molded product, it is preferable to appropriately adjust the monomer ratio so that the difference in the refractive index with the block copolymer (B) is 0.002 or less among the above ratios. . In addition, by using methyl methacrylate (c) in the above-mentioned ratio of 3 to 16% by weight, excellent heat resistance can be imparted to a molded product, and use in a high-temperature region or use in summer. In this case, excellent rigidity and surface impact strength can be exhibited. Furthermore, by using methyl methacrylate (c) in the above ratio, the styrene copolymer (A) can have a relatively low molecular weight while exhibiting an appropriate fluidity at the time of melting, and can be molded in good condition. Workability can be developed. Therefore, the styrene-based copolymer (A), which is a continuous layer, has appropriate flexibility, so that bending whitening of the molding sheet can be favorably prevented. From such a viewpoint, the styrene-based copolymer (A) is preferably a styrene-based copolymer having a mass average molecular weight of 25 × 10 ^{4 to} 35 × 10 ⁴ , and the melt mass flow rate is 5 to 12 g. / 10 min is preferable. As described above, since the styrene-based copolymer (A) can exhibit appropriate fluidity while keeping the molecular weight low, the styrene-based copolymer (A) and the block copolymer (B) can be combined with each other. Temperature conditions for melt-kneading can be set low. As a result, the occurrence of gelation during melt-kneading can be prevented, and the appearance of the finally obtained molded article becomes excellent.

  Such a styrene-based copolymer (A) can be obtained by polymerizing a styrene-based monomer (a), butyl acrylate (b), and methyl methacrylate (c) at a predetermined mass ratio. Examples of the polymerization method include a suspension polymerization polymerization method, a bulk suspension polymerization method, a solution polymerization method, and a bulk polymerization method, and a continuous bulk polymerization method is preferable in terms of productivity, cost, and uniformity of composition.

  In the present invention, the continuous bulk polymerization method particularly employs a polymerization apparatus having a polymerization line in which a plurality of tubular reactors are connected in series, and a mixing element disposed inside the tubular reactor. The continuous bulk polymerization method is preferred because a homogeneous styrene-based copolymer (A) can be efficiently produced.

  The mixing element used here is, for example, an SMX type or SMR type Sulzer type mixing element which changes the flow and direction of the flow of the polymerization liquid flowing into the pipe and repeats the division and merging. Tubular mixer, Kenix type static mixer, Toray type tubular mixer, and the like.

  In addition, in the continuous bulk polymerization method, before the raw material components are introduced into the polymerization apparatus, a stirring reactor is used in advance, and each raw material component is preliminarily polymerized in the stirring reactor. It is preferable to charge the polymerization liquid into a polymerization apparatus constituting a bulk polymerization line, since the uniformity of the obtained styrene-based copolymer (A) is further improved. Stirring reactors that can be used here include, for example, a stirring tank reactor, a stirring tower reactor, and the like, and stirring blades in the stirrer include, for example, an anchor type, a turbine type, a screw type, and a double type. Any of helical type, log bone type, etc. stirring blades can be used.

  The temperature conditions for performing the polymerization of each of the raw material components in a continuous polymerization line connecting such a stirring type reactor and a continuous bulk polymerization apparatus are as follows: the polymerization conversion rate is 120 to 135 in the initial stage of polymerization at a polymerization conversion rate of 35 to 55% by mass. C., and preferably in the range of 140 to 160 C. in the subsequent stage of polymerization. When such a temperature condition is satisfied, the control of the molecular weight of the obtained styrenic copolymer (A) becomes easy, and the productivity is remarkably improved.

  After completion of the polymerization, the polymerization solution is preheated in a preheater, then sent to a devolatilization tank, and after removing the unreacted monomers and the solvent under reduced pressure, pelletizing the styrene-based copolymer. The polymer (A) is obtained.

  In the continuous bulk polymerization method, a solvent may be used to reduce the viscosity of the polymerization solution in the tubular reactor. In this case, the used amount is 5 to 20 parts by mass based on 100 parts by mass of each raw material component in total. As the type of the solvent, ethylbenzene, toluene, xylene and the like which are usually used in the bulk polymerization method are suitable. It is preferable to add a chain transfer agent for controlling the molecular weight of the styrene copolymer (A). The amount of the chain transfer agent to be added is generally in the range of 0.005 to 0.5 parts by mass based on 100 parts by weight of the total amount of the raw material monomers.

  In the production of the styrenic copolymer (A), a polymerization initiator can be appropriately used. As the polymerization initiator, any general-purpose peroxide-based polymerization initiator can be used. In the present invention, among known peroxide-based polymerization initiators, the styrene-based copolymer (A) can be three-dimensionally polymerized, and the neck-in phenomenon at the time of sheet extrusion molding can be favorably prevented. 2-Bis (4,4-di-t-butylperoxycyclohexyl) propane is preferred.

Next, a block copolymer (B) composed of a polymer block (b1) of a styrene monomer and a polymer block (b2) of a conjugated diene monomer is as follows:
1) a diblock copolymer comprising a polymer block (b1) of a styrene monomer and a polymer block (b2) of a conjugated diene monomer;
2) A triblock composed of a polymer block (b1) of a styrene monomer, a polymer block (b2) of a conjugated diene monomer, and a polymer block (b1) of a styrene monomer. Copolymer,
3) a hydrogenated product of the triblock copolymer,
4) a multi-block copolymer comprising a plurality of polymer blocks exceeding a triblock consisting of a plurality of styrene monomer polymer blocks (b1) and a styrene monomer polymer block (b1); 5) a block copolymer having a random copolymerized portion in addition to the polymer block (b1) of the styrene monomer and the polymer block (b2) of the conjugated diene monomer,
And the like.

  Among these, the triblock copolymer 2) is preferable because the rubbery polymer (B) has excellent morphologically excellent surface impact resistance. In the triblock copolymer, the styrene monomer polymer block (b1) may be partially copolymerized with a conjugated diene monomer, or may be a conjugated diene monomer. In the polymer block (b2), a styrene monomer may be partially copolymerized.

  Here, the styrene monomer constituting the polymer block (b1) includes styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, ethylstyrene, isobutylstyrene, and t-methylstyrene. Butylstyrene, o-bromostyrene, m-bromostyrene, p-bromostyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene and the like. In the present invention, styrene is particularly preferred because it can easily form the above-mentioned alternately laminated state.

  Next, examples of the conjugated diene-based monomer constituting the polymer block (b2) include diene-based monomers such as butadiene, chloroprene, isoprene, and 1,3-pentadiene. Among these, the polybutadiene block is preferable because it is excellent in rubber elasticity expressed by the polymer block (b2) and can impart excellent surface impact strength to the finally obtained styrene resin composition of the present invention. preferable.

  Therefore, the block copolymer (B) is preferably a so-called styrene-butadiene copolymer (SBR), and the triblock type is preferably a styrene-butadiene-styrene copolymer (SBS). Styrene-butadiene-styrene copolymer (SBS) is preferred.

  Further, when the amount of the polymer block (b2) of the conjugated diene monomer in the block copolymer (B) increases, the rubber-like properties of the block copolymer (B) become strong, and plastic deformation occurs during molding. Since it is difficult to carry out, the content of the polymer block (b2) of the conjugated diene monomer in the block copolymer (B) is preferably 20 to 30% by mass.

  The block copolymer (B) described in detail above can be produced from a styrene monomer and a conjugated diene monomer by a known method such as emulsion polymerization or solution polymerization. In particular, when the triblock copolymer is produced, a styrene monomer and a diene monomer are solution-polymerized in a hydrocarbon organic solvent in the presence of an anionic polymerization initiator such as an organic lithium compound to form a triblock copolymer. Is preferred from the viewpoint of easily adjusting the molecular weight of the block copolymer (B) to high.

  The styrene-based resin composition of the present invention is obtained by melt-mixing the styrene-based copolymer (A) and the block copolymer (B). In the present invention, by melting and mixing the two, the layer of the styrene-based monomer polymer block (b1) and the conjugated diene-based block can be formed without destroying the morphology inherent in the block copolymer (B). The styrene-based copolymer (A) can be present as a continuous layer between layers in which layers of the monomer polymer block (b2) are alternately laminated.

  At this time, the mixing ratio of the styrene-based copolymer (A) and the block copolymer (B) is, as described above, a conjugated diene-based monomer which is a raw material component of the block copolymer (B). Is a ratio of 9 to 25% by mass in the styrene-based resin composition based on the mass ratio of the raw materials. If the abundance ratio of the structural unit derived from the conjugated diene-based monomer in the styrene-based resin composition of the present invention is less than 9% by mass, sufficient surface impact strength cannot be imparted to the molded product. On the other hand, if it exceeds 25% by mass, the rigidity of the composition itself becomes insufficient, and drawdown tends to occur during the secondary molding of the molding sheet. Among these ranges, a range of 14 to 25% by mass is particularly preferable because the surface impact strength is significantly improved. Further, the ratio of the structural unit derived from the methyl methacrylate (c) in the styrene resin composition is 1.5 to 6% by mass based on the mass ratio of the raw material, and the structure derived from the butyl acrylate (b). The styrene-based copolymer (A) and the block copolymer (B) are used so that the unit is 2.8 to 9.5% by mass in the styrene-based resin composition based on the raw material mass ratio. Is preferably mixed.

Here, the structural unit derived from the conjugated diene-based monomer means an alkylene structure site obtained by the addition reaction of the conjugated diene-based monomer. For example, 1,3-butadiene is used as a conjugated diene-based monomer. When used, they represent but-2-ene-1,4-diyl and but-3-en-1,2-diyl. The content of the structural unit in the styrene-based resin composition can be determined from the area ratio of the chemical peak corresponding to the carbon atom characteristic to each structural unit in C ¹³ -NMR measurement. For example, in the case of but-3-ene-1,2-diyl, the chemical shift of the terminal carbon atom constituting the 1,2-vinyl group is 114 ppm, and in the case of but-2-ene-1,4-diyl, the terminal carbon atom is The content of these structural units can be determined from the area ratio of the peaks of the chemical shift of 125 to 132 ppm.

  In addition, a specific method of melt-mixing the styrene-based copolymer (A) and the block copolymer (B) is, for example, to uniformly dry-blend the two with a mixer, and then mix the mixture with an extruder. A method of charging and melt-kneading, or a method of charging the styrene-based copolymer (A) and the block copolymer (B) into an extruder and melt-kneading them.

  For example, pellets or pearls of the styrene copolymer (A) and the block copolymer (B) are dry-blended in advance using a mixer such as a Banbury mixer, and the resulting mixture is charged into an extruder, or Alternatively, there is a method in which pearls are directly charged into an extruder and melt-kneaded at 190 to 240 ° C. by the extruder. The melt-kneaded mixture may be directly formed into a sheet, or may be formed into pellets once and then formed again into a molten sheet by an extruder. Examples of the method of melt-kneading include, for example, a method of melt-kneading with a single-screw and twin-screw extruder, a kneader, and an open roll. In addition, the resin temperature at the time of extrusion is a melting temperature of the styrene-based copolymer (A) and the block copolymer (B) in order to suppress gel formation and improve the appearance of a molded product, And it is preferable that it is 210 degrees C or less.

  In the present invention, when the styrene-based copolymer (A) and the block copolymer (B) are polymerized from each raw material component, or when both are melt-kneaded, an antioxidant and a mold release agent are appropriately used. Various additives such as an agent, an ultraviolet absorber, a colorant, a heat stabilizer, a plasticizer, and a dye may be mixed. These additives can be added during kneading or during polymerization of each polymer. Specific examples of such additives include mineral oils, plasticizers such as ester plasticizers and polyester plasticizers, antioxidants, chain transfer agents, higher fatty acids, higher fatty acid esters, metal salts of higher fatty acids, and silicon oil. And these may be used alone or in combination of two or more.

  In the present invention, in order to further improve the surface impact strength, the structural unit of the styrene monomer is adjusted to 50% by mass or less, and the polymer block of the styrene monomer and the conjugated diene monomer are adjusted. A block copolymer composed of a polymer block and a styrene resin composition can be added to the styrene resin composition at a ratio of 2 to 15% by mass in the styrene resin composition.

  As a method for producing a molding sheet from the styrene-based resin composition of the present invention, the styrene-based copolymer (A) and the block copolymer (B) are melt-kneaded by the method described above, and then a T-die is used. And a method of forming a sheet by a calender molding method and an inflation extrusion molding method. In this way, a sheet having a thickness of 0.02 to 3 mm, preferably 0.03 to 1 mm, suitable for secondary molding can be produced.

  The sheet for molding thus obtained is excellent in transparency, surface impact strength, rigidity, resistance to bending whitening, and moldability. For example, as for transparency, the sheet cloud value using a 0.4 mm thick sheet based on JIS K7105 is 5 or less. Further, the surface impact strength is 0.8 J or more in DuPont impact strength with a sheet having a thickness of 0.4 mm, exhibiting an unprecedented performance. Further, the heat resistance of the molded product is also improved, and the molded product does not deform under high temperature and high humidity conditions (for example, a temperature of 65 ° C., a humidity of 80%, and a standing time of 8 hours).

  In the present invention, the molding sheet can be further shaped into a desired shape by air pressure molding, heat and pressure molding, or the like. Since the molding sheet has bending whitening resistance, is excellent in balance between surface impact strength and rigidity, and has good moldability, it can be used, for example, in blister packages, food packaging trays, lids, cups, and various types of containers. It can be applied to applications such as trays, carrier tapes, shrink films, etc., and is particularly useful as a blister package because of its excellent bending whitening resistance and good heat resistance.

  On the other hand, the styrene-based resin composition of the present invention can be applied not only to the above-mentioned sheet application but also to a shrink film. Examples of a method for producing a shrink film include a method in which the styrene-based resin composition of the present invention is melt-kneaded, extruded, and stretched in at least one direction.

  The method of stretching the shrink film is not particularly limited, and a method of stretching uniaxially or biaxially, simultaneously or sequentially, is preferable.

  Here, the stretching method is, in the case of flat uniaxial stretching, mainly stretching in the extrusion direction at a speed difference between heating rolls, or in the direction perpendicular to the extrusion direction with a tenter or the like, and in the case of biaxial stretching, A method in which the film is longitudinally stretched in the extrusion direction at a speed difference between the heating rolls and then horizontally stretched in a tenter or the like, or simultaneously stretched vertically and horizontally in a tenter.

  In the case of annular uniaxial stretching, there is a method in which the draft is adjusted by stretching the sheet extruded in a cylindrical shape while suppressing expansion in the cross-sectional diametric direction of the bubble. In this case, there is a method in which the sheet is stretched by an extrusion method, and simultaneously or sequentially stretched in the sectional diameter direction of the bubble while blowing air into the inside of the bubble of the sheet extruded in a cylindrical shape.

  Further, the transparent styrene-based resin composition of the present invention, in addition to the respective uses of the sheet and shrink film, rigidity, surface impact, rich in moldability, injection molding from the point that even more excellent transparency can be expressed, It can be applied to various molding applications such as profile extrusion molding, vacuum molding, air pressure molding and the like, and can also be used as housings and parts for home appliances, various parts for OA equipment, stationery, miscellaneous goods and the like.

  ADVANTAGE OF THE INVENTION According to this invention, the surface impact strength in the molded article of a styrene resin composition can be improved remarkably, and the balance between surface impact strength and rigidity can be improved.

  Furthermore, in addition to preventing appearance defects due to whitening at the time of bending or impact of the molding sheet, excellent transparency and heat resistance can be imparted to a secondary molded product of the molding sheet. Therefore, the styrene resin composition of the present invention is extremely useful for applications such as blister packages, food packaging trays, lids, cups, various storage trays, carrier tapes, shrink films, and the like.

Next, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. The “parts” or “%” below are based on mass unless otherwise specified.
[Production of styrenic copolymer (A)]
For the production of the styrene copolymer (A), a continuous polymerization apparatus comprising a polymerization line shown in the process diagram shown in FIG. 3 was used. The polymerization apparatus includes a plunger pump (1), a stirring reactor (2), a gear pump (3), (7), (11), a tubular reactor (4) having a mixing element disposed therein, (5), (6), (8), (9), and (10). In FIG. 3, the arrows indicate the direction of the flow of the polymerization liquid. The raw material components are first sent to the stirred reactor (2) by the plunger pump (1), and the initial graft polymerization is performed under stirring. By the gear pump (3), it is introduced into the circulation polymerization line (I) composed of the tubular reactors (4), (5), (6) and the gear pump (7), and the circulation polymerization line (I) If the polymerization solution is circulated inside, polymerization is performed. On the other hand, the tubular reactors (8), (9), (10) and the gear pump (11) form a non-circulating polymerization line (II), and one of the polymerization liquids in the circulation line (I) is formed. The part flows into the polymerization line (II), and polymerization is performed in the polymerization line (II) to a desired degree of polymerization.

  Here, the polymerization in the circulating polymerization line (I) is performed by reacting the styrene monomer (a) with butyl acrylate (b) and methyl methacrylate (c) at the outlet of the circulating polymerization line (I). The polymerization is carried out so that the total polymerization conversion is usually 35 to 55% by mass, preferably 40 to 50% by mass. The ratio of the flow rate of the polymerization liquid circulating in the circulation type polymerization line (I) to the flow rate of the polymerization liquid flowing out of the non-circulation type polymerization line (II), and the reflux ratio R, are output to the polymerization line (II). The flow rate of the mixed solution refluxing in the circulation polymerization line (I) is set to F1 (liter / hour), and the flow rate F2 of the mixed solution flowing from the circulation polymerization line (I) to the non-circulation polymerization line (II) is F2 ( Liter / hour), R = F1 / F2 is usually adjusted in the range of 3 to 15.

  After the polymerization is completed, the polymerization solution is sent to a preheater and then to a devolatilization tank by a gear pump (11), and after removing unreacted monomers and a solvent under reduced pressure, pelletizing the styrene-based copolymer. The polymer (A) is obtained.

(Production of styrene-based copolymer (A-1))
A mixed solution comprising 82 parts of styrene (SM), 12 parts of butyl acrylate (BuA), 6 parts of methyl methacrylate (MMA), and 8 parts of ethylbenzene was prepared. 0.025 parts of 2,2-bis (4,4-di-peroxycyclohexyl) propane and 0.01 part of n-dodecylmercaptan as a chain transfer agent per 100 parts of the monomer mixture were added to the polymerization apparatus. Was used for continuous bulk polymerization under the following conditions.

Reaction temperature in stirred reactor (2): 115 ° C
Reaction temperature in the circulation polymerization line (I): 132 ° C
Reaction temperature in polymerization line (II): 150 ° C
Next, the mixed solution obtained by the polymerization was heated to 215 ° C. with a heat exchanger to remove volatile components under reduced pressure, and then pelletized to obtain a styrene-based copolymer (A-1). Table 1 shows the physical properties of the obtained styrenic copolymer.

(Production of styrene copolymer (A-2))
A mixed solution consisting of 82 parts of styrene (SM), 12 parts of butyl acrylate (BuA), 6 parts of methyl methacrylate (MMA) and 9 parts of ethylbenzene was added as a polymerization initiator in an amount of 0.025 to 100 parts of the monomer mixture. Parts of 2,2-bis (4,4-di-peroxycyclohexyl) propane and a styrene copolymer except that 0.02 parts of n-dodecyl mercaptan were added as a chain transfer agent to 100 parts of the monomer mixture. A styrenic copolymer (A-2) was obtained in the same manner as the polymer (A-1). Table 1 shows the physical properties of the obtained styrenic copolymer.

(Production of styrene copolymer (A-3))
A mixed solution consisting of 82 parts of styrene (SM), 8 parts of butyl acrylate (BuA), 10 parts of methyl methacrylate (MMA) and 9 parts of ethylbenzene was used as a polymerization initiator in an amount of 0.025 to 100 parts of the monomer mixture. Parts of 2,2-bis (4,4-di-peroxycyclohexyl) propane and a styrene-based copolymer except that 0.03 part of n-dodecylmercaptan was added to 100 parts of the monomer mixture as a chain transfer agent. A styrenic copolymer (A-3) was obtained in the same manner as in the polymer (A-1). Table 1 shows the physical properties of the obtained styrenic copolymer.

(Production of styrene copolymer (A-4))
A mixed solution consisting of 82 parts of styrene (SM), 5 parts of butyl acrylate (BuA), 13 parts of methyl methacrylate (MMA), and 6 parts of ethylbenzene was added as a polymerization initiator in an amount of 0.025 to 100 parts of the monomer mixture. Part of t-butyl peroxyisopropyl monocarbonate, 0.03 part of n-dodecyl mercaptan was added to 100 parts of the monomer mixture as a chain transfer agent, and the polymerization line shown in the process diagram of FIG. Under the conditions, bulk polymerization was continuously performed.

Reaction temperature in the stirred reactor (2): 119 ° C
Reaction temperature in the circulation polymerization line (I): 124 ° C
Reaction temperature in polymerization line (II): 150 ° C
The mixed solution obtained by the polymerization was heated to 215 ° C. with a heat exchanger, volatile components were removed under reduced pressure, and then pelletized to obtain a styrene-based copolymer (A-4). Table 1 shows the physical properties of the obtained styrenic copolymer.

(Production of styrene-based copolymer (A-5))
A mixed solution consisting of 82 parts of styrene (SM), 5 parts of butyl acrylate (BuA), 13 parts of methyl methacrylate (MMA) and 9 parts of ethylbenzene was added as a polymerization initiator in an amount of 0.025 to 100 parts of the monomer mixture. Parts of 2,2-bis (4,4-di-peroxycyclohexyl) propane and a styrene-based copolymer except that 0.03 part of n-dodecylmercaptan was added to 100 parts of the monomer mixture as a chain transfer agent. A styrenic copolymer (A-5) was obtained in the same manner as in the polymer (A-1). Table 1 shows the physical properties of the obtained styrenic copolymer.

(Production of styrene-based copolymer (A-6))
In a mixed solution consisting of 82 parts of styrene (SM), 18 parts of butyl acrylate (BuA) and 9 parts of ethylbenzene, 0.026 parts of 2,2-bis (4 , 4-di-peroxycyclohexyl) propane was added, and continuous bulk polymerization was carried out using the polymerization line shown in the process diagram of FIG. 3 under the following conditions.
Reaction temperature in stirred reactor (2): 115 ° C
Reaction temperature in circulation polymerization line (I): 132 ° C
Reaction temperature in non-circulation polymerization line (II): 150 ° C
The mixed solution obtained by the polymerization was heated to 215 ° C. with a heat exchanger, volatile components were removed under reduced pressure, and the mixture was pelletized to obtain a styrene copolymer (A-6). Table 1 shows the physical properties of the obtained styrenic copolymer.

[Production of styrene resin composition and evaluation of physical properties]
(Styrene-butadiene-styrene block copolymer (B))
The styrene-butadiene-styrene block copolymer (B) used in each of the following Examples and Comparative Examples is as follows.

Styrene-butadiene-styrene block copolymer (B1):
Chevron Phillips SBS (trade name “K Resin KR05”)
Content of structural units derived from styrene: 75% by mass
Content of structural units derived from butadiene: 25% by mass
MFR: 7g / 10min

Styrene-butadiene-styrene block copolymer (B2)
Chevron Phillips SBS (trade name “K Resin DK11”
Content of structural units derived from styrene: 75% by mass,
Content of structural units derived from butadiene: 25% by mass,
MFR: 8 g / 10 min. )
Hereinafter, the styrene-butadiene-styrene block copolymers (B1) and (B2) are abbreviated as “block copolymer (B1)” and “block copolymer (B2)”, respectively.

(Measured by ^C 13 -NMR)
Structural units derived from the conjugated diene-based monomer in the styrene-based resin compositions obtained in each of Examples and Comparative Examples, structural units derived from methyl methacrylate (c), and derived from butyl acrylate (b) The content of the structural unit to be measured was measured as follows.

  120 mg of the sample obtained in each example or comparative example was dissolved in 0.5 ml of CDC13, and about 5 mg of a relaxation reagent was added to the solution and filled in a sample tube for NMR measurement. Quantitative 13 C-NMR was measured by a gate coupling method using NMR “GSX-400” manufactured by JEOL Ltd.

  The content of each structural unit was determined from the area ratio of the chemical peaks of carbon atoms shown below.

In the case of a carbon atom to be measured and a corresponding chemical shift styrene-derived structural unit, an aromatic carbon atom: 142 to 146 ppm
In the case of a structural unit derived from methyl methacrylate, a carbonyl carbon atom:
175ppm
In the case of a structural unit derived from butyl acrylate, the carbon atom of the butyl group bonded to the oxygen atom: 63 ppm
In the case of a structural unit derived from butadiene (but-3-ene-1,2-diyl), a terminal carbon atom constituting a 1,2-vinyl group: 114 ppm
In the case of a structural unit derived from butadiene (but-2-ene-1,4-diyl), a terminal carbon atom: 125 to 132 ppm

[Physical property evaluation method]
The methods for evaluating the physical properties of the molding sheet in each of the following Examples and Comparative Examples are as follows.

(Haze measurement)
In accordance with JIS K7105, a haze value indicating the transparency of a 0.4 mm-thick sheet test piece was measured using a turbidity and haze meter (manufactured by Nippon Denshoku Industries Co., Ltd.).

(Measurement of DuPont impact strength)
Using a DuPont impact tester (manufactured by Toyo Seiki Seisaku-Sho, Ltd.), the 50% breaking energy of a 0.4 mm-thick sheet test piece was determined under the conditions of a weight of 300 g, a tip radius of the shooting core of 6.3 mm, and a cradle radius of 6.3 mm. Was.

(Measurement of tensile modulus)
The tensile modulus was measured at a test speed of 1 mm / min in accordance with JIS K7161.

(Measurement of melt mass flow rate)
Based on JIS K7210, the melt mass flow rate was measured at a temperature of 200 ° C. and a load of 5 kgf.

(Bending whitening test)
A 0.4 mm thick sheet was bent at 180 °, and then the thickness of the whitened portion when the sheet was returned to the original state was measured with a vernier caliper.

(Evaluation of sheet appearance)
The extruded sheet was evaluated as ○ when no appearance defects such as fish eyes, hard spots and sharkskin were generated, and evaluated as x when it did.

(Heat resistance evaluation)
A 0.4 mm thick sheet is formed into a 170 × 130 × 35 (mm) box by a vacuum forming machine, and the formed product is left in a constant temperature bath at a temperature of 65 ° C. and a humidity of 80% for 8 hours to deform the formed product. It was confirmed. The case where no deformation was observed in the molded product was evaluated as ○, and the case where it was deformed was evaluated as ×.

(Measurement of neck-in)
Extruded sheet of width (W) were measured, and the die width as W _0, was calculated neck-in from the following equation.

Neck-in _{(mm) =} W 0 -W

Example 1
The following styrene-butadiene-styrene block copolymer (B1) was added to the styrene-based copolymer (A-1) at a mass ratio of (A-1) / (B1) = 50/50, and extruded. A sheet having a thickness of 0.4 mm was prepared.

  Various physical properties were measured using the obtained sheet. The measured values are shown in Table 3. The sheet forming conditions are as follows.

Sheet forming machine: UEV type 30mm extruder manufactured by Union Plastics Co., Ltd. Cylinder temperature: 210 ° C, T-die set temperature: 210 ° C
T-die lip width: 200mm
Pickup speed: 1m / min
Screw rotation speed: 65 rpm

Example 2
The block copolymer (B2) was added to the styrene-based copolymer (A-1) at a mixing ratio of (A-1) / (B2) = 40/60, and the thickness was reduced to 0 under the same conditions as in Example 1. A sheet of 0.4 mm was prepared and various physical properties were measured. The measured values are shown in Table 2.

Example 3
The block copolymer (B2) was added to the styrene-based copolymer (A-1) at a mixing ratio of (A-1) / (B2) = 40/60 to a thickness of 0.4 mm under the following extrusion conditions. Sheets were prepared and various physical properties were measured.

<Extrusion conditions>
Sheet forming machine: 120mm extruder manufactured by Hitachi Zosen Corporation Cylinder temperature: 210 ° C, T-die set temperature: 210 ° C
T-die lip width: 1030mm
Pickup speed: 22m / min
Screw rotation speed: 60rpm
Further, a part of the sheet was cut out, stained with osmium tetroxide, ultra-thin sections were prepared from a cross section in the CD direction with an ultramicrotome, and a transmission electron microscope (TEM) was photographed. The results are shown in FIG.

Example 4
The block copolymer (B2) was added to the styrene-based copolymer (A-1) at a mixing ratio of (A-1) / (B2) 30/70, and a thickness of 0.1 was obtained under the same conditions as in Example 1. A 4 mm sheet was prepared and various physical properties were measured. The measured values are shown in Table 2.

Example 5
The block copolymer (B1) was added to the styrene-based copolymer (A-2) at a mixing ratio of (A-3) / (B1) = 50/50, and a thickness of 0 was obtained under the same conditions as in Example 1. A sheet of 0.4 mm was prepared and various physical properties were measured. The measured values are shown in Table 3.

Example 6
The block copolymer (B1) was added to the styrene-based copolymer (A-3) at a mass ratio of (A-4) / (B1) = 50/50, and a thickness of 0 was obtained under the same conditions as in Example 1. A sheet of 0.4 mm was prepared and various physical properties were measured. The measured values are shown in Table 3.

Example 7
A block copolymer (B1) and a styrene-butadiene block having a styrene monomer structural unit content of 43% by mass and a butadiene monomer structural unit content of 57% by mass in a styrene copolymer (A-1). A copolymer elastomer ("TR2003" manufactured by JSR Corporation) was added at a ratio of (A-1) / (B1) / (TR2003) = 40/50/10, and a thickness of 0 was obtained under the same conditions as in Example 1. A sheet of 0.4 mm was prepared and various physical properties were measured. The measured values are shown in Table 3.

Example 8
The block copolymer (B1) was added to the styrene-based copolymer (A-4) at a mixing ratio of (A-4) / (B1) = 50/50, and a thickness of 0 was obtained under the same conditions as in Example 1. A sheet of 0.4 mm was prepared and various physical properties were measured. The measured values are shown in Table 3.

Example 9
The block copolymer (B1) was added to the styrene-based copolymer (A-5) at a mixing ratio of (A-5) / (B1) = 50/50, and a thickness of 0 was obtained under the same conditions as in Example 1. A sheet of 0.4 mm was prepared and various physical properties were measured. The measured values are shown in Table 3.

Example 10
The block copolymer (B1) was added to the styrene-based copolymer (A-1) at a mixing ratio of (A-5) / (B1) = 40/60, and the thickness was reduced to 0 under the same conditions as in Example 1. A sheet of 0.4 mm was prepared and various physical properties were measured. The measured values are shown in Table 3.

Comparative Example 1
The block copolymer (B1) was added to the styrene-based copolymer (A-6) at a mixing ratio of (A-6) / (B1) = 40/60, and the thickness was reduced to 0 under the same conditions as in Example 1. A sheet of 0.4 mm was prepared and various physical properties were measured. The measured values are shown in Table 4.

Comparative Example 2
The block copolymer (B2) was added to the styrene-based copolymer (A-6) at a mixing ratio of (A-6) / (B1) = 40/60, and the thickness was reduced to 0 under the same conditions as in Example 1. A sheet of 0.4 mm was prepared and various physical properties were measured. The measured values are shown in Table 4.

  In addition, a part of the obtained sheet was cut out, stained with osmium tetroxide, ultra-thin sections were prepared from a cross section in the CD direction using an ultramicrotome, and photographed with a transmission electron microscope (TEM). FIG. 2 shows the results.

Comparative Example 3
The block copolymer (B2) was added to the styrene-based copolymer (A-6) at a mixing ratio of (A-6) / (B1) = 30/60, and a thickness of 0 was obtained under the same conditions as in Example 1. A sheet of 0.4 mm was prepared and various physical properties were measured. The measured values are shown in Table 4.

(Note that "TR2003" in the table is a thermoplastic elastomer "TR2003" manufactured by JSR Corporation (styrene-butadiene block copolymer having a styrene monomer structural unit content of 43% by mass and a butadiene monomer structural unit content of 57% by mass). Union).)

FIG. 1 is a transmission electron microscope (TEM) photograph of the styrene resin composition obtained in Example 3. FIG. 2 is a transmission electron microscope (TEM) photograph of the styrene resin composition obtained in Comparative Example 2. FIG. 3 is a process diagram showing an example of a continuous bulk polymerization line incorporating a tubular reactor having a mixing element disposed therein.

Explanation of reference numerals

(1): Plunger pump
(2): Stirred reactor
(3): Gear pump
(4): A tubular reactor having a mixing element disposed inside
(5): A tubular reactor having a mixing element disposed inside
(6): Tubular reactor having a mixing element disposed inside
(7): Gear pump
(8): Tubular reactor having a mixing element disposed inside
(9): A tubular reactor having a mixing element disposed inside
(10): tubular reactor having a mixing element disposed inside
(11): Gear pump
(I): Circulation polymerization line
(II): Non-circulation type polymerization line

Claims (8)

A styrene-based copolymer (A) and a block copolymer (B) composed of a polymer block of a styrene-based monomer (b1) and a polymer block of a conjugated diene-based monomer (b2) are included. A styrenic resin composition,
The styrene-based copolymer (A) is a copolymer of a styrene-based monomer (a), butyl acrylate (b) and methyl methacrylate (c),
The block copolymer (B) has a multilayer structure in which layers of the polymer block (b1) and layers of the polymer block (b2) of diene-based monomers are alternately laminated; and
A styrene-based resin composition comprising a structural unit derived from the conjugated diene-based monomer in a ratio of 9 to 25% by mass in the styrene-based resin composition in terms of a raw material mass ratio. The styrene-based resin composition according to claim 1, wherein the styrene-based resin composition contains structural units derived from the methyl methacrylate (c) in a ratio of 1.5 to 6% by mass in the styrene-based resin composition based on the raw material mass ratio. The styrene-based resin according to claim 1 or 2, wherein the styrene-based resin composition contains a structural unit derived from the butyl acrylate (b) in a ratio of 2.8 to 9.5% by mass in the styrene-based resin composition. Composition. The styrene copolymer (A) is a copolymer of 78 to 85% by mass of a styrene monomer (a), 6 to 19% by mass of butyl acrylate (b), and 3 to 16% by mass of methyl methacrylate (c). A polymer, and the block copolymer (B) contains a polymer block (b2) of a conjugated diene-based monomer in the block copolymer (B) at a ratio of 20 to 30% by mass. The styrenic resin composition according to claim 1, wherein The styrenic resin composition according to claim ⁴ , wherein the styrenic copolymer (A) is a styrenic copolymer having a mass average molecular weight of 25 x 10 ^{4 to} 35 x 10 ⁴ . The block copolymer (B) composed of the styrene monomer polymer block (b1) and the conjugated diene monomer polymer block (b2) has a mass average molecular weight of 130,000 to 170, The styrene resin composition according to claim 1, wherein the styrene resin composition has a molecular weight distribution (Mw / Mn) of 1.3 to 1.7. A molding sheet comprising the styrene resin composition according to claim 1. A blister package comprising the styrene resin composition according to claim 1.

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