JP2011148915A - Polylactic acid-based sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polylactic acid-based sheet excellent in antistatic properties, printability, blocking resistance, and processability and especially suitable for printing applications. <P>SOLUTION: The polylactic acid-based sheet includes a surfactant-applied layer on at least one surface of a polylactic acid-based substrate having a degree of surface orientation ΔP of 0-0.002. The surfactant-applied layer mainly includes an organic sulfonic acid-type surfactant and has specific surface resistivity of less than 1×10<SP>13</SP>Ω/sq. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a polylactic acid-based sheet that is excellent in antistatic properties, printability, blocking resistance, and processability, and is particularly suitable for printing applications.

  In recent years, global warming due to an increase in the concentration of carbon dioxide in the atmosphere has become a global problem, and various industrial fields are actively developing technologies to reduce carbon dioxide emissions into the atmosphere. . In the field of plastic products, conventionally, plastics produced from general-purpose petroleum-derived raw materials have been incinerated after use and released into the atmosphere as carbon dioxide gas. Attention is focused on plant-derived plastics derived from gas. In particular, research and development for the practical use of polylactic acid, which is excellent in transparency and relatively advantageous in terms of cost, is thriving.

  Also in the field of film / sheet, it is expected as a material to replace polyolefin resin, polyester resin, polystyrene resin and acrylic resin by making use of transparency.

  However, since the polylactic acid resin itself has a high degree of electrical insulation, it is very easy to be charged, and the generation and accumulation of static electricity causes various problems in secondary processing such as printing and molding. . Further, since dust and dust are easily adsorbed, there is a problem that the appearance is impaired.

  Generally, as a method for imparting antistatic properties to plastic films and sheets, anionic surfactants such as anionic, cationic and nonionic surfactants or a polymeric surfactant are kneaded into the film / sheet, / The method of apply | coating to the surface of a sheet | seat is employ | adopted (patent document 1, patent document 2).

JP 10-36650 A Japanese Patent Application Laid-Open No. 9-221587

  However, when the conventional method is applied to a polylactic acid-based sheet, the additive that has antistatic performance is blended by the kneading method disclosed in Patent Document 1, and the means for imparting antistatic properties is satisfactory antistatic. In order to satisfy the antistatic performance, a large amount of a low molecular weight additive has to be blended, and there has been a problem that the properties of the sheet / film are remarkably impaired and the appearance is deteriorated.

  Further, as disclosed in Patent Document 2, the method of applying an antistatic agent to the surface of a film / sheet to impart antistatic properties can satisfactorily achieve antistatic properties, but the adhesion of printing ink in printing applications. There is a problem of ink dropout due to insufficient properties, and also causes a problem in secondary processing such as blocking when the coated surfaces are overlapped, such as during sheet storage.

  Therefore, the development of a sheet having practicality is effective in the antistatic performance and secondary processing performance effective for the polylactic acid-based sheet, particularly in printing applications.

  In view of the background of such prior art, the present invention is intended to provide a polylactic acid-based sheet that is excellent in antistatic properties, printability, and blocking resistance and that is particularly suitable for printing applications.

The present invention employs the following means in order to solve the above problems.
(1) A polylactic acid-based sheet having a surfactant coating layer on at least one surface of a polylactic acid-based substrate having a plane orientation degree ΔP of 0 or more and 0.002 or less,
The surfactant coating layer mainly contains an organic sulfonic acid type surfactant,
A polylactic acid sheet having a surface resistivity of less than 1 × 10 ¹³ Ω / □.
(2) Haze (%) is 10% or less, The polylactic acid-type sheet | seat as described in said (1) characterized by the above-mentioned.
(3) When all the components of the polylactic acid-based substrate are 100% by mass, the polylactic acid-based substrate contains 90% by mass to less than 100% by mass of polylactic acid, and the soft component exceeds 0% by mass. The polylactic acid sheet according to any one of (1) to (3), wherein the polylactic acid sheet is contained in an amount of 10% by mass or less.

  ADVANTAGE OF THE INVENTION According to this invention, the polylactic acid-type sheet | seat excellent in antistatic property, printability, blocking resistance, and workability and especially suitable for printing use is provided. By using the sheet of the present invention, it is possible to obtain a printed material with a low environmental load without impairing the printability of a conventional petroleum resin sheet.

  The polylactic acid-based sheet of the present invention is excellent in printability and can be used as a printed matter. Moreover, since it is excellent in moldability, it is also suitable for molding applications. Examples of the printed matter made of the polylactic acid sheet of the present invention include clear files, novelty products such as desk calendar cases, card products such as member cards and prepaid cards, and container products such as clear cases. In particular, a clear file or a desktop calendar case is suitable because it is possible to use ruled lines while being transparent.

  Hereinafter, the polylactic acid-based sheet of the present invention will be described. In the following, “sheet” is used to mean a two-dimensional structure such as a film or a plate, and “processed product” is a container such as a printed material or a three-dimensional structure. For example, it is used to mean that the sheet is processed.

  The polylactic acid used for the polylactic acid-based substrate of the polylactic acid-based sheet of the present invention is composed of L-lactic acid and / or D-lactic acid as a main component, and all the monomers in which lactic acid-derived components constitute polylactic acid. A component of 100 mol% to 70 mol% or more and 100 mol% or less is preferred, and homopolylactic acid consisting essentially of L-lactic acid and / or D-lactic acid is preferably used.

  The polylactic acid used in the present invention preferably has crystallinity. The polylactic acid has crystallinity when the polylactic acid is sufficiently crystallized under heating and then subjected to differential scanning calorimetry (DSC) measurement in an appropriate temperature range. Says that heat of fusion is observed. In general, homopolylactic acid has higher melting point and crystallinity as the optical purity is higher. The melting point and crystallinity of polylactic acid are affected by the molecular weight and the catalyst used during polymerization, but normally, homopolylactic acid with an optical purity of 98% or higher has a melting point of about 170 ° C. and relatively high crystallinity. Further, as the optical purity is lowered, the melting point and crystallinity are lowered. For example, the homopolylactic acid having an optical purity of 88% has a melting point of about 145 ° C., and the homopolylactic acid having an optical purity of 75% has a melting point of about 120 ° C. . Homopolylactic acid with an optical purity lower than 70% does not show a clear melting point and is amorphous.

  The polylactic acid used for the polylactic acid-based substrate of the polylactic acid-based sheet of the present invention is a homopolylactic acid having a crystallinity and an amorphous property for the purpose of imparting or improving a necessary function depending on the use of the polylactic acid-based sheet. It is also possible to mix homopolylactic acid. In this case, the proportion of amorphous homopolylactic acid may be determined within a range that does not impair the effects of the present invention. When a relatively high heat resistance is desired when a polylactic acid-based substrate is used, it is preferable that at least one of the polylactic acids used includes polylactic acid having an optical purity of 95% or more.

  The mass average molecular weight of the polylactic acid used for the polylactic acid-based substrate of the polylactic acid-based sheet of the present invention is usually at least 50,000 or more, preferably 80,000 to 400,000, more preferably 100,000 to 300,000. Here, the mass average molecular weight is a molecular weight calculated by a polymethyl methacrylate conversion method after measurement with a chloroform solvent by gel permeation chromatography (GPC).

  By setting the mass average molecular weight of the polylactic acid to at least 50,000, the mechanical properties of the sheet of the present invention having a polylactic acid-based substrate containing the polylactic acid can be improved, and further the sheet of the present invention. The mechanical property of the processed product made of can also be made excellent.

  The polylactic acid used for the polylactic acid-based substrate of the polylactic acid-based sheet of the present invention is a copolymerized polylactic acid obtained by copolymerizing other monomer components having ester forming ability in addition to L-lactic acid and D-lactic acid. It may be. Examples of copolymerizable monomer components include glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid, 6-hydroxycaproic acid, and other hydroxycarboxylic acids, as well as ethylene glycol, propylene glycol, and butane. Compounds containing a plurality of hydroxyl groups in the molecule such as diol, neopentyl glycol, polyethylene glycol, glycerin, pentaerythritol or their derivatives, succinic acid, adipic acid, sebacic acid, fumaric acid, terephthalic acid, isophthalic acid, 2 , 6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, 5-tetrabutylphosphonium sulfoisophthalic acid and the like, or compounds containing a plurality of carboxylic acid groups in the molecule. In addition, it is preferable to select the component which has biodegradability among the above-mentioned copolymerization components according to a use. These copolymer components are preferably contained in an amount of 0 mol% to 30 mol% in 100 mol% of all monomer components constituting polylactic acid.

  Next, the method for producing the polylactic acid-based substrate of the polylactic acid-based sheet of the present invention will be specifically described.

  The polylactic acid used for the polylactic acid-based substrate of the polylactic acid-based sheet of the present invention can be obtained, for example, by the following method. As a raw material, a lactic acid component of L-lactic acid or D-lactic acid is mainly used, and a hydroxycarboxylic acid other than the lactic acid component described above can be used in combination. Further, a cyclic ester intermediate of hydroxycarboxylic acid, for example, lactide, glycolide, etc. can be used as a raw material. Furthermore, dicarboxylic acids and glycols can also be used.

  Polylactic acid can be obtained by a method of directly dehydrating and condensing the raw materials or a method of ring-opening polymerization of the cyclic ester intermediate. For example, in the case of producing by direct dehydration condensation, lactic acid or lactic acid and hydroxycarboxylic acid are preferably subjected to azeotropic dehydration condensation in the presence of an organic solvent, particularly a phenyl ether solvent, and particularly preferably a solvent distilled by azeotropic distillation. A polymer having a high molecular weight can be obtained by polymerizing by a method in which water is removed from the solvent and the solvent is brought into a substantially anhydrous state and returned to the reaction system.

  It is also known that a high molecular weight polymer can be obtained by subjecting a cyclic ester intermediate such as lactide to ring-opening polymerization under reduced pressure using a catalyst such as tin octylate. At this time, a method for adjusting the conditions for removing moisture and low molecular weight compounds during heating and refluxing in an organic solvent, a method for suppressing the depolymerization reaction by deactivating the catalyst after completion of the polymerization reaction, and a method for heat-treating the produced polymer Can be used to obtain a polymer with a small amount of lactide.

  In the present invention, as the polylactic acid-based substrate, for example, a film obtained by an existing film production method such as a T-die casting method, an inflation method, or a calendar method can be used. A film by a T-die casting method in which polylactic acid is melt-kneaded and extruded by using T. is preferable. For example, as an example of a production method by T-die casting, polylactic acid having a moisture content of 400 ppm or less is obtained by drying the chip at 60 to 110 ° C. for 3 hours or more, and the cylinder temperature at the time of melt kneading is 150 ° C. The range of -240 degreeC is preferable, and it is more preferable to set it as the range of 200 degreeC-220 degreeC from the meaning which prevents deterioration of polylactic acid. The T die temperature is also preferably in the range of 200 ° C. to 220 ° C. After being extruded from the T die, the sheet is about 0.1 mm to 1.0 mm in thickness by cooling with a cooling roll of 5 to 50 ° C. (Polylactic acid base material) is obtained. Furthermore, it is preferable to perform various surface treatments on the obtained sheet (polylactic acid-based substrate) for the purpose of improving coating suitability. Examples of the surface treatment include corona discharge treatment, plasma treatment, flame treatment, acid treatment, etc., and any method can be used, but continuous treatment is possible, and equipment for existing film forming equipment is used. Corona discharge treatment can be exemplified as the most preferable because of its easy installation and simple processing.

  In the present invention, the thickness of the polylactic acid-based substrate is not particularly limited, but is usually about 0.1 mm to 1.0 mm. When the polylactic acid-based sheet of the present invention is used as a processed product, the thickness of the polylactic acid-based substrate is preferably about 0.15 mm to 0.7 mm, and the polylactic acid-based sheet of the present invention is printed. When used as an application, the polylactic acid base material preferably has a thickness of about 0.1 mm to 0.4 mm.

  In the present invention, the polylactic acid-based substrate is a known antioxidant, UV stabilizer, anti-coloring agent, matting agent, deodorant, flame retardant, weathering agent as long as the effects of the present invention are not impaired. In addition, various additives such as antioxidants, ion exchangers, crystal nucleating agents, color pigments, or lubricants, inorganic fine particles, organic particles, and organic lubricants may be added as necessary, effectively expressing the function. In order to make it preferable content, it is 0.1 to 1.0 mass% in 100 mass% of all the components of a polylactic acid-type base material.

  Examples of the antioxidant include hindered phenols and hindered amines.

  Color pigments include inorganic pigments such as carbon black, titanium oxide, zinc oxide, iron oxide, cyanine, styrene, phthalocyanine, anthraquinone, perinone, isoindolinone, quinophthalone, quinocridone, thio Organic pigments such as indigo can be used.

  As inorganic particles, silicon oxide such as silica, various carbonates such as calcium carbonate, magnesium carbonate and barium carbonate, various sulfates such as calcium sulfate and barium sulfate, various composite oxides such as kaolin and talc, lithium phosphate, Fine particles comprising various phosphates such as calcium phosphate and magnesium phosphate, various oxides such as aluminum oxide, titanium oxide and zirconium oxide, various salts such as lithium fluoride and the like can be used.

  As the organic particles, fine particles made of calcium oxalate, terephthalate such as calcium, barium, zinc, manganese, magnesium, or the like are used. Examples of the crosslinked polymer particles include fine particles made of a vinyl monomer such as divinylbenzene, styrene, acrylic acid or methacrylic acid, or a copolymer. In addition, organic fine particles such as polytetrafluoroethylene, benzoguanamine resin, thermosetting epoxy resin, unsaturated polyester resin, thermosetting urea resin, and thermosetting phenol resin are also preferably used.

  The average particle diameter of both inorganic particles and organic particles is not particularly limited, but is preferably 0.01 to 5 μm, more preferably 0.05 to 4.5 μm, and most preferably 0.08 to 4.0 μm.

  Examples of organic lubricants include liquid paraffins, natural paraffins, synthetic paraffins, aliphatic hydrocarbons such as polyethylene, stearic acid, lauric acid, hydroxystearic acid, fatty castors such as hard castor oil, stearic acid amide, oleic acid amide, Fatty acid amides such as erucic acid amide, lauric acid amide, ethylene bis stearic acid amide, ethylene bis oleic acid amide, ethylene bis lauric acid amide, fatty acid metal salts such as aluminum stearate, lead stearate, calcium stearate, magnesium stearate , Fatty acid (partial) esters of polyhydric alcohols such as glycerin fatty acid esters and rubitan fatty acid esters, long chain fatty acid esters such as long chain ester waxes such as butyl stearate and montan wax And the like. Among these, stearic acid amide and ethylene bis-stearic acid amide, which are easy to obtain an effect in a small amount due to appropriate compatibility with polylactic acid, are preferable.

  It is important that the polylactic acid-based sheet of the present invention has a surfactant coating layer on at least one surface of a polylactic acid-based substrate having a plane orientation degree ΔP of 0 or more and 0.002 or less. It is important that the surfactant coating layer formed on at least one surface of the polylactic acid-based substrate mainly contains an organic sulfonic acid type surfactant.

  Here, the surfactant coating layer mainly contains an organic sulfonic acid type surfactant in that 100% by mass of all components of the surfactant coating layer, the surfactant coating layer contains 50 mass of the organic sulfonic acid type surfactant. % To 100% by mass or less. The surfactant coating layer preferably contains 80% by mass or more and 100% by mass or less of an organic sulfonic acid type surfactant in 100% by mass of all components of the surfactant coating layer, and is 90% by mass or more and 100% by mass or less. More preferably, it is more preferably 98% by mass or more and 100% by mass.

  The organic sulfonic acid type surfactant used for the surfactant has high antistatic properties, and has good adhesion between the polylactic acid-based substrate and the surfactant coating layer and the adhesion between the polylactic acid-based sheet of the present invention and the ink. The printability can be improved.

  When an organic sulfonic acid type surfactant and another surfactant, particularly a nonionic surfactant, are used in combination as the surfactant, moisture absorption is likely to occur at high humidity, causing a problem that sheets are blocked. Therefore, when the surfactant coating layer contains a surfactant other than the organic sulfonic acid type surfactant, the amount is preferably less than 1% by mass in 100% by mass of all the components of the surfactant coating layer. .

  As a surfactant, an organic sulfonic acid type surfactant is mainly used, so that antistatic properties can be imparted in a smaller amount compared to the case where other surfactants are used in combination. Become.

  By setting the degree of plane orientation ΔP of the polylactic acid-based substrate in the present invention to 0 or more and 0.002 or less, the workability at the time of molding or ruled line processing can be improved. In the case of an oriented sheet, that is, a sheet having a plane orientation degree ΔP exceeding 0.002, there is a problem that the forming method and conditions are limited and the processing condition width is narrowed when forming or ruled line processing. The plane orientation degree ΔP is more preferably 0.0005 or more and 0.001 or less.

  The method for setting the degree of plane orientation ΔP of the polylactic acid-based substrate to 0 or more and 0.002 or less is not particularly limited. For example, a method of extruding from a T die and then cooling and solidifying with a casting roll at 5 to 50 ° C. Can be mentioned. In cold stretching such as biaxial stretching (stretching at a temperature below the melting point), the degree of plane orientation ΔP may be greater than 0.002.

  Various organic sulfonic acid type surfactants can be applied. Such an organic sulfonic acid type surfactant is composed of an organic sulfonic acid and a base.

  The organic sulfonic acid constituting the organic sulfonic acid type surfactant is 1) alkyl such as octyl sulfonic acid, dodecyl sulfonic acid, tetradecyl sulfonic acid, stearyl sulfonic acid, tetracosyl sulfonic acid, 2-ethylhexyl sulfonic acid, etc. Alkyl sulfonic acid having 8 to 24 carbon atoms, 2) aromatic sulfonic acid such as phenyl sulfonic acid and naphthyl sulfonic acid, 3) octyl phenyl sulfonic acid, dodecyl phenyl sulfonic acid, dibutyl phenyl sulfonic acid, dinonyl phenyl sulfonic acid Alkylbenzene sulfonic acid having 6 to 18 carbon atoms in the alkyl group, and 4) alkylnaphthalene sulfonic acid having 2 to 18 carbon atoms in the alkyl group, such as 4) dimethylnaphthylsulfonic acid, diisopropylnaphthylsulfonic acid, dibutylnaphthylsulfonic acid, etc. Can be mentioned.

  Bases constituting the organic sulfonic acid type surfactant include 1) alkali metals such as sodium, potassium and lithium, 2) phosphonium such as tetrabutylphosphonium, tributylbenzylphosphonium, triethylhexadecylphosphonium and tetraphenylphosphonium, 3 ) Ammonium such as tetrabutylammonium, tributylbenzylammonium, triphenylbenzylammonium and the like.

  As the organic sulfonic acid type surfactant mainly contained in the surfactant coating layer of the polylactic acid-based sheet of the present invention, those obtained by appropriately combining the above-described organic sulfonic acid and base can be applied. As the sulfonic acid, an alkyl sulfonate having 8 to 24 carbon atoms in the alkyl group, an alkylbenzene sulfonate having 6 to 18 carbon atoms in the alkyl group, and an alkyl naphthalene sulfonate having 2 to 18 carbon atoms in the alkyl group are preferable. Specifically, tetradecyl sulfonate, dodecyl phenyl sulfonate, and dimethyl naphthyl sulfonate are more preferable, and more specifically, sodium tetradecyl sulfonate, sodium dodecyl phenyl sulfonate, sodium dimethyl naphthyl sulfonate, and dodecyl phenyl. Lithium sulfonate is particularly preferred

  In the present invention, the surfactant coating layer formed on at least one surface of the polylactic acid-based substrate may be various resins, for example, resins such as acrylic polymers, as long as the object of the present invention is not impaired. May be included.

  In the present invention, as a method for forming a surfactant coating layer on at least one surface of a polylactic acid-based substrate, various coating methods can be applied, and are not particularly limited. For example, a roll coating method, a gravure coating method, a wire The bar method, reverse coating method, air knife coating method, curtain flow method, spray coating method, and dipping method may be applied alone or in combination.

  In the present invention, it is preferable to use a so-called in-line coating method when a surfactant is applied on a polylactic acid-based substrate to form a surfactant coating layer. Since this method does not use an organic solvent and requires only one process, there is little decrease in mechanical strength in terms of physical properties, and in terms of process, there is no loss of the raw material of the sheet because it is a single process. It is beneficial to.

In the present invention, the solid content coating amount of the surface active agent coating layer ^is preferably ^{1mg / m 2 ~50mg / m 2} . When the solid content coating amount of the surfactant is less than 1 mg / m ² , the antistatic property becomes insufficient. On the other hand, when it exceeds 50 mg / m ² , blocking tends to occur. More preferably from ^{10mg / m 2 ~30mg / m 2} . The polylactic acid-based sheet of the present invention is a sheet having a surfactant coating layer on at least one surface of a polylactic acid-based substrate. Therefore, the coating liquid for forming the surfactant coating layer can be applied to only one side or both sides of the polylactic acid base material depending on the use of the sheet. A uniform coating film is obtained by drying after application. It is preferable to perform drying after application | coating of the coating liquid for surfactant coating layer formation for 2 to 60 second at 60 to 90 degreeC.

It is important that the surface specific resistance value of the polylactic acid-based sheet of the present invention is less than 1.0 × 10 ¹³ Ω / □. When the surface specific resistance value is 1.0 × 10 ¹³ Ω / □ or more, in the secondary processing, the running property of the sheet in the processing machine is deteriorated and blocking due to charging is remarkable. The surface specific resistance value is preferably as small as possible, but if it is about 1.0 × 10 ¹⁰ Ω / □, it is a sufficient value when printing a polylactic acid-based sheet for use as a printing application. .

  The polylactic acid sheet of the present invention preferably has a haze of 10% or less. If the haze is 10% or less, it is a processed product using such a sheet, and it is preferably used as a processed product having high design properties such as excellent color appearance and good appearance as a product, particularly in printing applications. be able to. When the haze is larger than 10%, the transparency is insufficient, which may not be preferable for practical use. Further, if the haze is less than 1%, the sheet is easily scratched, and when such a sheet is printed, the appearance may be deteriorated. Therefore, the more preferable haze of the polylactic acid-based sheet of the present invention is It is 1% or more and 10% or less, more preferably 2% or more and 8% or less.

  In order to adjust the haze to 10% or less, the haze can be controlled by changing the content of the soft component in the polylactic acid-based substrate or by containing inorganic particles or organic particles as necessary. More specifically, the haze can be brought close to 10% by increasing the content of the soft component. In order to bring the haze closer to 1%, the reverse operation is possible. Moreover, if the content of the particles in the polylactic acid-based substrate is increased, the haze can be brought close to 10%.

  In the present invention, the polylactic acid-based substrate preferably contains polylactic acid and a soft component. When the total component of the polylactic acid-based substrate is 100% by mass, the polylactic acid-based substrate is polylactic acid. It is preferable to contain 90 mass% or more and less than 100 mass%, and also contains a soft component more than 0 mass% and 10 mass% or less. When 100% by mass of the total components of the polylactic acid-based substrate is less than 90% by mass of polylactic acid or more than 10% by mass of the soft component, the plant degree is lowered and the advantage of using polylactic acid is reduced. End up. When 100% by mass of the total component of the polylactic acid-based substrate does not contain a soft component and the amount of polylactic acid is 100% by mass, there are problems such as a decrease in impact resistance of the sheet and a decrease in transparency. More preferably, in 100% by mass of all components of the polylactic acid-based substrate, the polylactic acid-based substrate contains 98% by mass to 99% by mass of polylactic acid and 1% by mass to 2% by mass of the soft component. .

  Examples of the soft component include an ethylene-propylene copolymer, an ethylene / propylene-nonconjugated diene copolymer, an ethylene-1-butene copolymer, an ethylene-acrylic acid copolymer and an alkali metal salt thereof (so-called ionomer), ethylene -Glycidyl (meth) acrylate copolymer, ethylene-acrylic acid alkyl ester copolymer (for example, ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer), acid-modified ethylene-propylene copolymer, Diene rubber (for example, polybutadiene, polyisoprene, polychloroprene), copolymer of diene and vinyl monomer (for example, styrene-butadiene random copolymer, styrene-butadiene block copolymer, styrene-butadiene-styrene block copolymer) Coalescence, styrene-isopropyl Copolymer, styrene-isoprene block copolymer, styrene-isoprene-styrene block copolymer, polybutadiene grafted with styrene, butadiene-acrylonitrile copolymer), polyester-diol dicarboxylic acid block Copolymer, polyisobutylene, copolymer of isobutylene and butadiene or isoprene, natural rubber, thiocol rubber, polysulfide rubber, acrylic rubber, silicone rubber, polyurethane rubber, polyether rubber, epichlorohydrin rubber, aliphatic polyester, polyester Based elastomers and polyamide based elastomers.

  Further, the soft component used for the polylactic acid base material of the polylactic acid-based sheet of the present invention includes those having various degrees of crosslinking, those having various microstructures such as cis structure and trans structure, core layer and the like. A multilayer structure polymer composed of one or more shell layers to be covered can be used.

  As a soft component used for the polylactic acid base material of the polylactic acid-based sheet of the present invention, an aliphatic polyester other than polylactic acid is preferable. Furthermore, it is preferable to use a polybutylene succinate resin in order to improve impact resistance while maintaining transparency and to maintain the biodegradability of the polylactic acid sheet. More preferred are polybutylene succinate and polybutylene succinate adipate, which have a large impact resistance improving effect and are compatible with polylactic acid.

  There are no particular limitations on the method of melt-kneading the polylactic acid and the soft component, and a commonly used mixer such as a kneader, roll mill, Banbury mixer, single-screw or twin-screw extruder can be used. Among these, from the viewpoint of productivity, it is preferable to use a single screw or twin screw extruder.

  The mixing order is not particularly limited. For example, a polybutylene succinate resin, which is a polylactic acid and a soft component, is dry blended and then supplied to a melt kneader, or a master batch in which polylactic acid and a soft component are melt kneaded in advance. And a method of melt-kneading the master batch and polylactic acid. In addition, if necessary, a method of melt-kneading other components at the same time, or a method of preparing a master batch in which polylactic acid and other additives are melt-kneaded in advance, and then melt-kneading the master batch and polylactic acid are used. Also good.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by a following example.
[Measurement and evaluation method]
Measurements and evaluations shown in the examples were performed under the following conditions.

(1) Antistatic property Based on JIS-K6911 (established in 1962), the surface of the coated surface of the coated sheet using a resiliency chamber manufactured by ADC Co., Ltd. and a digital ultrahigh resistance / microammeter The specific resistance value was measured in an atmosphere at a temperature of 23 ° C. and a humidity of 65%.

(2) Printability (A) Adhesiveness between polylactic acid-based substrate and surfactant coating layer The adhesion between the polylactic acid-based substrate and the surfactant coating layer was evaluated by an antifogging test. First, an adhesive tape (24 mm width made by Nichiban Co., Ltd.) was applied to the coated surface of a coating sheet provided with a surfactant coating layer on the surface of a polylactic acid-based substrate. Is immediately peeled off, and 300 ml of hot water at about 80 ° C. is put into a 500 ml beaker, and then the coated surface including the portion where the tape is peeled off is placed on the beaker and held for about 15 seconds. The cloudiness of the surface was observed. The appearance was evaluated in four stages.
○: Not fogged at all.
Δ: A slight part becomes cloudy.
X: Cloudiness is confirmed as a whole.
(B) Adhesion between coating sheet and ink Using an ultraviolet curable ink (UV STP Indigo manufactured by T & K TOKA), an ink layer was applied to a thickness of about 2 μm on the coating sheet by a roll coating method. Thereafter, ultraviolet rays having an irradiation intensity of 80 W / cm ² were irradiated for 8 seconds at an irradiation distance of 9 cm and cured to prepare a sample.

The adhesion between the coated sheet and the ink was evaluated by tape peeling using a cross-cut method described in JIS-K5600 (established in 1999). First, six parallel vertical and horizontal parallel lines were drawn at 1 mm intervals on a sample piece using a cutter knife to produce 36 squares in a grid pattern. Adhesive tape (“Cello Tape (registered trademark)” 24 mm width manufactured by Nichiban Co., Ltd., 24 mm width) is pasted on these grids, and after evenly adhering, the adhesive tape is peeled off instantaneously and the ink layer of the test piece is peeled off. Was evaluated based on the following criteria from the proportion of the cells remaining without peeling.
○: 90% or more Δ: 50% or more and less than 90% ×: less than 50% (3) Two anti-blocking coated sheets are cut into A4 size and 200 g in a state where the coated surfaces of the coated sheets are overlapped. A load of / cm ² was applied and left for 24 hours in an atmosphere of 40 ° C., and then the peeling state of the stacked sheets was observed.
○: No blocking. Good peeling.
(Triangle | delta): Although interference spots are seen, it peels easily.
X: Interference spots are seen, and there are places where peeling is difficult.

(4) Haze (%)
According to JIS-K7105 (established in 1981), haze was measured using a haze meter HGM-2DP type (manufactured by Suga Test Instruments Co., Ltd.). The measurement was performed three times per level, and was determined from the average value of the three measurements. In addition, when the surfactant coating layer was formed only on one side of the substrate, the measurement was performed from the surfactant coating layer side.

(6) Degree of plane orientation ΔP
Using an automatic birefringence meter KOBRA-21ADH manufactured by Oji Scientific Instruments Co., Ltd., birefringences Δx, Δy, Δz in the three principal axis directions of the sheet-like sample are obtained, and Δx = γ-β, Δy = γ-α, Δz = A-β (γ ≧ β, α is the refractive index in the thickness direction of the sheet).
ΔP = {(γ + β) / 2} −α = (Δy−Δz) / 2
[Polylactic acid used]
(PLA-1):
Homopolylactic acid having a mass average molecular weight = 220,000, D-form content = 5.0 mol%, melting point = 150 ° C., water content = 330 ppm.

In addition, said mass mean molecular weight was measured using Japan Waters Co., Ltd. product Warters2690, polymethylmethacrylate as a standard, column temperature of 40 degreeC, and the chloroform solvent.
[Soft ingredients used]
(FL-1):
Polybutylene succinate resin (Mitsubishi Chemical Corporation, trade name “GsPla” FZ71PD)
(FL-2):
Polylactic acid-diol / dicarboxylic acid block copolymer (manufactured by Dainippon Ink & Chemicals, trade name “Puramate” PD-150)
(FL-3):
Core-shell type acrylic polymer (Rohm & Haas, trade name “Paraloid” BPM500)
[Used inorganic particle masterbatch]
(IP-1):
Silica (10% by mass in 100% by mass of masterbatch) / PLA-1 (90% by mass in 100% by mass of masterbatch) based masterbatch (silica average particle size: 3.4 to 4.0 μm)
[Surfactant used]
(SA-1):
Alkyl sulfonate (trade name “Elecut” C-052, manufactured by Takemoto Yushi Co., Ltd.)
(SA-2):
Sodium alkyl sulfonate (trade name “Chemistat” 3033N, manufactured by Sanyo Chemical Co., Ltd.)
(SA-3):
Acrylic polymer / alkyl sulfonate mixture (manufactured by Takemoto Yushi Co., Ltd., trade name “Elecut” C-031K)
(SA-4):
Acrylic polymer / alkyl sulfonate mixture (manufactured by Takemoto Yushi Co., Ltd., trade name “Elecut” C-037)
(SA-5):
Coconut fatty acid diethanolamide (manufactured by Sanyo Kasei Co., Ltd., trade name “Chemistat” 2500)
[Preparation of polylactic acid sheet]
Example 1
PLA-1, FL-1, and IP-1 were supplied to a vented twin screw extruder at a blending ratio (mass ratio) of 93: 2: 5, melt-kneaded while degassing the vacuum vent, and the die temperature Was co-extruded from a T die die set at 220 ° C., sandwiched between metal casting drums whose surface temperature was adjusted to 40 ° C., and solidified by cooling to produce a base sheet having a thickness of 0.2 mm, and then one side at a time. Corona treatment is applied to both surfaces, and an aqueous coating solution of surfactant SA-1 is applied to both surfaces one by one by a gravure roll method, dried through a drying furnace, and finally the coating amount shown in Table 1 is obtained. After forming the surfactant coating layer, the coating sheet was wound up with a winder.

  The evaluation results of the obtained sheet are shown in Table 1.

(Example 2)
A polylactic acid sheet was obtained in the same manner as in Example 1 except that the coating amount of the surfactant described in Table 1 was changed.

(Example 3)
A polylactic acid-based sheet was used in the same manner as in Example 1 except that the soft component described in Table 1 was used and the blending ratio (mass ratio) of PLA-1, FL-2, and IP-1 was changed to 90: 5: 5. Got.

Example 4
Polylactic acid was used in the same manner as in Example 1 except that PLA-1, FL-3, and IP-1 were used and the blending ratio (mass ratio) was changed to 87: 8: 5 using the soft ingredients listed in Table 1. A system sheet was obtained.

(Examples 5 and 6)
A polylactic acid-based sheet was obtained in the same manner as in Example 1 except that the type of surfactant described in Table 1 was changed.

(Example 7)
A polylactic acid sheet was obtained in the same manner as in Example 1 except that SA-2 and SA-5 were used as the surfactant and the blending ratio (mass ratio) was changed to 99.5: 0.5.

(Comparative Examples 1, 2, 4)
A polylactic acid-based sheet was obtained in the same manner as in Example 1 except that the type and amount of surfactant described in Table 1 were changed.

(Comparative Example 3)
Example 1 except that the blending ratio (mass ratio) of PLA-1, FL-1, and IP-1 was changed to 90: 5: 5, and the surfactant types and application amounts described in Table 1 were changed. Similarly, a polylactic acid sheet was obtained.
(Comparative Example 5)
A base sheet was prepared in the same manner as in Example 1, and a polylactic acid base sheet was obtained without applying a surfactant.

  The polylactic acid-based sheets of Examples 1 to 6 were excellent in antistatic property, printability, and blocking resistance in any sheet. In Example 7, although the blocking resistance was slightly inferior, the antistatic property and the printability were excellent.

  On the other hand, in the comparative examples, each sheet was inferior in one or more of any of the antistatic properties, printability, and anti-blocking properties, and was clearly different from the examples. Comparative Examples 1 to 4 are considered to have such a result because the surfactant coating layer contains less than 50% by mass of the organic sulfonic acid type surfactant. On the other hand, Comparative Example 5 is considered to have such a result because it does not have a surfactant coating layer.

Claims (3)

A polylactic acid-based sheet having a surfactant coating layer on at least one surface of a polylactic acid-based substrate having a plane orientation degree ΔP of 0 or more and 0.002 or less,
The surfactant coating layer mainly contains an organic sulfonic acid type surfactant,
A polylactic acid sheet having a surface resistivity of less than 1 × 10 ¹³ Ω / □.   2. The polylactic acid-based sheet according to claim 1, wherein the haze (%) is 10% or less. When all the components of the polylactic acid base material are 100% by mass, the polylactic acid base material contains 90% by mass or more and less than 100% by mass of polylactic acid, and more than 0% by mass and 10% by mass of the soft component. The polylactic acid-based sheet according to any one of claims 1 to 3, further comprising: