JP2012066388A - Polylactic acid resin sheet and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polylactic acid resin sheet having superior cost and dimensional stability, which is especially suitable for a cutter, and to provide a method of manufacturing the same.SOLUTION: (1) The polylactic acid resin sheet is a non-extended sheet mainly consisting of a polylactic acid resin, and is characterized in that the amount Rh (mm) of sheet warpage return when processing at 80°C for one hour fulfills the following condition: Rh≤2. (2) The polylactic acid resin sheet of the above (1) has the thickness of at least 150 μm, and is characterized in that when the two-dimensional center line average roughness of one surface of the sheet is Ra1 (μm), and the two-dimensional center line average roughness of the other surface is Ra2 (μm), the following conditions are fulfilled: 0.005≤|Ra1-Ra2|≤0.2, wherein the surfaces of Ra1 and Ra2 are chosen so that Ra1<Ra2.

Description

  The present invention relates to a polylactic acid resin sheet that is excellent in step stability and particularly suitable for a cutter, and a method for producing the same.

  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 application of polylactic acid-based resins, which are excellent in transparency and rigidity and relatively advantageous in terms of cost, are active. On the other hand, polylactic acid-based resins have the drawback of low dimensional stability, and improvements are desired.

  On the other hand, in paper packaging containers such as wrap film storage cases, metal and paper cutters have conventionally been used as wrap film cutters. From the viewpoint of ease of separation and disposal after use and durability Plastic cutters are starting to be used. Among them, in consideration of the above-mentioned environmental problems such as global warming, polylactic acid film cutters are being studied by various companies.

  Patent Documents 1 and 2 disclose a technique related to a film cutter obtained by stretching a polylactic acid resin in a biaxial direction.

  Patent Document 3 discloses a technique related to a film cutter containing an inorganic substance in a polylactic acid resin.

JP-A-11-99498 JP 2006-263892 A JP-A-2005-212064

  Sheets that have been biaxially stretched as in the technologies described in Patent Documents 1 and 2 are subjected to a stretching process, so the processing cost remains high, and they are supplied inexpensively and industrially to widely used everyday products such as wrap films. There was a problem that it was not practical.

  In the technique described in Patent Document 3, there is no improvement in thermal dimensional stability especially when the sheet is exposed to a high temperature such as in summer, and the sheet is warped when subjected to heat, and the cutting property is reduced. There was a problem that would be lost.

  Thus, the present invention has been achieved as a result of intensive studies aimed at solving the above-mentioned problems, and is intended to provide a polylactic acid resin sheet that is excellent in cost and dimensional stability and particularly suitable for a cutter. is there.

The present invention employs the following means in order to solve the above problems.
(1) An unstretched sheet mainly composed of a polylactic acid-based resin,
A polylactic acid resin sheet characterized in that a sheet curl amount Rh (mm) when treated at 80 ° C. for 1 hour satisfies the following conditions.
Rh ≦ 2
(2) The thickness is 150 μm or more,
When the two-dimensional centerline average roughness of one surface of the sheet is Ra1 (μm) and the two-dimensional centerline average roughness of the other surface is Ra2 (μm), the following condition is satisfied: (1) The polylactic acid-based resin sheet according to the above.
0.005 ≦ | Ra1-Ra2 | ≦ 0.2
(However, the surfaces of Ra1 and Ra2 are selected so that Ra1 <Ra2.)
(3) A cutter comprising the polylactic acid resin sheet according to (1) or (2).
(4) In a sheet manufacturing method having a step of niping a sheet-like molten polymer with a pair of cooling rolls (R0 and R1) and subsequently taking it into close contact with the cooling roll R1,
Rotation speed V ₀ which cooling roll R0 _(m / min), and the rotation speed V ₁ of the cooling roll R1 _(m / min), polylactic acid-based resin sheet manufacturing method, wherein the following condition is satisfied.
1.03V ₁ ≦ V ₀ ≦ 1.15V ₁
(5) The method for producing a polylactic acid resin sheet according to (4), wherein the rotational speed V ₀ satisfies the following condition.
12 m / min ≦ V ₀ ≦ 40 m / min (6) The surface temperature T ₀ (° C.) of the cooling roll R ₀ and the surface temperature T ₁ (° C.) of the cooling roll R ₁ satisfy the following conditions: (4) The manufacturing method of the polylactic acid-type resin sheet as described in (5).
20 ≦ T ₀ , T ₀ + 3 ≦ T ₁ ≦ 45

  ADVANTAGE OF THE INVENTION According to this invention, the polylactic acid-type resin sheet excellent in cost and dimensional stability and especially suitable for cutters is provided. If the polylactic acid-type resin sheet of this invention is used, a cutter with a low environmental load can be obtained without impairing dimensional stability. Moreover, according to the manufacturing method of this invention, the polylactic acid-type resin sheet suitable for cutters can be manufactured suitably.

  Hereinafter, the polylactic acid resin 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.

  It is important that the polylactic acid resin sheet of the present invention is an unstretched sheet mainly made of polylactic acid resin.

  The term “unstretched” in the present invention means that a so-called stretching process has not been performed. Specifically, the sheet is uniaxially or in a state where the sheet is at a temperature not lower than the glass point transition temperature of the polylactic acid resin and not higher than the melting point. It means that the process of extending 1.1 times or more in the biaxial direction has not been performed. Here, mainly means that the polylactic acid-based resin is 60% by mass or more and 100% by mass or less in the entire sheet of 100% by mass. When the content of the polylactic acid resin is less than 60% by mass, the degree of biomass is lowered, and the significance of using the polylactic acid resin is diminished.

  In addition, when a sheet | seat is a laminated structure, mainly means that polylactic acid-type resin is 60 mass% or more and 100 mass% or less in the whole 100 mass% of several layers.

  The polylactic acid-based resin sheet of the present invention is an unstretched sheet mainly composed of a polylactic acid-based resin, and it is important that the sheet curl amount Rh (mm) when treated at 80 ° C. for 1 hour is Rh ≦ 2. It is.

  When Rh ≦ 2, when used as a cutter, the cutter blade does not warp and has excellent cutting properties. In particular, when it is applied as a film cutter used around a kitchen, it may be exposed to a relatively high temperature, and heat-resistant dimensional stability is required and can be met.

  In the case of R> 2, when used as a cutter, the object to be cut is caught on the cutter blade which is warped, so that the cutting property is impaired, which is not preferable.

  The sheet warp phenomenon occurs because there is an internal strain difference on both sides of the sheet. In order to suppress sheet warpage and satisfy Rh ≦ 2, it is eliminated by suppressing the internal strain difference between both surfaces of the sheet.

  The method for satisfying Rh ≦ 2 in the polylactic acid-based resin sheet of the present invention is not particularly limited. For example, the sheet-like molten polymer is nipped by a pair of cooling rolls (R0 and R1), and then cooled. A sheet manufacturing method (hereinafter referred to as a manufacturing method by a nip method) having a step of pulling while being in close contact with the roll R1 is preferable.

  In the method of casting a molten polymer on a cooling roll which is mainly applied to the production of a thin film, there is no nip roll (roll corresponding to the above-mentioned R0), and only one side of the sheet is cooled. A difference in cooling rate occurs, and as a result, an internal strain difference occurs on both sides of the sheet, and the sheet tends to warp.

  On the other hand, in the manufacturing method by the nip method using a pair of cooling rolls, since both sides of the sheet are cooled using the cooling roll R0 and the cooling roll R1, an internal strain difference is less likely to occur on both sides of the sheet. It is difficult for warping to occur.

To meet Rh ≦ 2 is the manufacturing method according to the above-mentioned nip system, the rotational speed _V 0 which cooling roll R0 (m / min), and the rotation speed _V 1 of the cooling roll R1 (m / min), 1. It is preferable that 03V ₁ ≦ V ₀ ≦ 1.15V ₁ is satisfied.

In the case of V ₀ <1.03 V ₁ , the sheet-like molten polymer surface on the cooling roll R1 side has a higher melt tension than the sheet surface on the R0 side, so the internal strain of the sheet on the R1 side increases, and R1 An internal strain difference occurs between the R0 side and the R0 side, and Rh exceeds 2.

In the case of V ₀ > 1.15 V ₁ , since the sheet-like molten polymer is pulled to the cooling roll R 0 side, the film formation becomes unstable and the flatness of the sheet is impaired.

In the manufacturing method according nip system, a more preferable range of the relationship between the rotational speed _{V 1} of the rotational speed _{V 0} and the cooling roll R1 of the cooling roll R0 is _{1.05V 1 ≦ V 0 ≦ 1.10V 1} .

Moreover, in the manufacturing method by the above-mentioned nip method, in order to satisfy Rh ≦ 2, it is preferable that the rotational speed V ₀ (m / min) of the cooling roll R0 satisfies 12 m / min ≦ V ₀ ≦ 40 m / min.

When V ₀ <12 m / min, the productivity is inferior, resulting in an increase in production cost.

In addition, when V ₀ > 40 m / min, the sheet is wound up without being sufficiently cooled, so that the flatness is impaired.

In the manufacturing method by the nip method, a more preferable range of the rotational speed V ₀ (m / min) of the cooling roll R0 is 15 m / min ≦ V ₀ ≦ 30 m / min.

Further, in the manufacturing method using the nip method, in order to satisfy Rh ≦ 2, the surface temperature T ₀ (° C.) of the cooling roll R ₀ and the surface temperature T ₁ (° C.) of the cooling roll R ₁ are 20 ≦ T ₀ , It is preferable to satisfy T ₀ + 3 ≦ T ₁ ≦ 45.

In the case of T ₀ <20, lactide generated due to thermal decomposition of the polylactic acid resin adheres to the surface of the cooling roll R 0, and the sheet surface becomes dirty.

In the case of T ₀ +3> T ₁ , the sheet sticks to the cooling roll R 0 side, film formation becomes unstable, and the flatness of the sheet is impaired.

In the case of T ₁ > 45, the sheet is not sufficiently cooled, so that the sheet is poorly peeled from the cooling roll, the film formation becomes unstable, and the flatness of the sheet is impaired.

In the manufacturing method according nip system, a more preferable range of the surface temperature _{T 1} of the surface temperature _{T 0} and the cooling roll R1 of the cooling roll R0 is _{25 ≦ T 0, T 0 +} 3 ≦ T 1 ≦ 40.

  The surface temperatures of the cooling roll R0 and the cooling roll R1 can be adjusted by electrically heating the temperature of the fluid heat medium circulated inside the cooling roll.

  The polylactic acid resin sheet of the present invention has a thickness of 150 μm or more, the two-dimensional centerline average roughness of one surface of the sheet is Ra1 (μm), and the two-dimensional centerline average roughness of the other surface is Ra2. (Μm), 0.005 ≦ | Ra1−Ra2 | ≦ 0.2 (however, the surfaces of Ra1 and Ra2 are selected so that Ra1 <Ra2 is satisfied) is preferably satisfied.

  When the total thickness of the sheet is less than 150 μm, there is no rigidity. In particular, when the sheet is used as a cutter, there may be a problem that the cutter is deformed when the cutter cuts the workpiece.

  In addition, when the total thickness of the sheet exceeds 500 μm, in particular, when used as a cutter, there may be a problem such as poor cutting performance. Therefore, the total thickness of the sheet is preferably 500 μm or less.

  When the two-dimensional surface roughness | Ra1-Ra2 | is smaller than 0.005 μm, the roll is likely to be blocked. When the sheet is drawn out during molding after winding up into a roll, the sheets are blocked and smoothly formed. Since drawing cannot be performed, there is a problem that the processing speed is reduced.

  On the other hand, when | Ra1-Ra2 | is larger than 0.2 μm, there is a problem that the sheets are easily slipped and thus easily cause winding deviation after being rolled up. Furthermore, when used as a film cutter, if 0.005 ≦ | Ra1-Ra2 | ≦ 0.2, for example, when the film is pulled out from the film container for food packaging, the film and the cutter slide exactly and easily. The film can be pulled out.

In the present invention, the method of 0.005 ≦ | Ra1−Ra2 | ≦ 0.2 is not particularly limited. For example, the rotational speed V ₀ of the cooling roll R0 is 12 m / min ≦ V ₀ ≦ by the nip roll method described above. 40 m / min, and the surface temperature T ₀ (° C.) of the cooling roll R ₀ and the surface temperature T ₁ (° C.) of the cooling roll R ₁ satisfy 20 ≦ T ₀ and T ₀ + 3 ≦ T ₁ ≦ 45. .

  The polylactic acid resin used in the present invention is mainly composed of L-lactic acid and / or D-lactic acid, and lactic acid-derived components are 70 mol in 100 mol% of all monomer components constituting the polylactic acid resin. A homopolylactic acid resin substantially consisting of only L-lactic acid and / or D-lactic acid is preferably used.

  Moreover, it is preferable that the polylactic acid-type resin used for this invention has crystallinity. The polylactic acid resin has crystallinity when the polylactic acid resin is sufficiently crystallized under heating and then subjected to differential scanning calorimetry (DSC) measurement in an appropriate temperature range. This means that the heat of crystal melting derived from is observed. Usually, the higher the optical purity of the homopolylactic acid resin, the higher the melting point and crystallinity. The melting point and crystallinity of the polylactic acid resin are affected by the molecular weight and the catalyst used at the time of polymerization. Usually, the homopolylactic acid resin having an optical purity of 98% or more has a melting point of about 170 ° C. and relatively low crystallinity. high. Further, as the optical purity is lowered, the melting point and crystallinity are lowered. For example, a homopolylactic acid resin having an optical purity of 88% has a melting point of about 145 ° C., and a homopolylactic acid resin having an optical purity of 75% has a melting point of 120. It is about ℃. A homopolylactic acid resin having an optical purity lower than 70% does not show a clear melting point and becomes amorphous.

  The polylactic acid-based resin used in the present invention is mixed with a crystalline homopolylactic acid-based resin and an amorphous homopolylactic acid-based resin for the purpose of imparting or improving a necessary function depending on the use used as a laminated sheet. It is also possible. In this case, the ratio of the amorphous homopolylactic acid resin may be determined within a range that does not impair the effects of the present invention. In addition, when a relatively high heat resistance is desired when a laminated sheet is used, it is preferable that at least one of the polylactic acid resins used includes a polylactic acid resin having an optical purity of 95% or more.

  The weight average molecular weight of the polylactic acid resin used in the present invention is usually at least 50,000, preferably 80,000 to 400,000, and more preferably 100,000 to 300,000. In addition, the weight average molecular weight as used in the field of this invention means the molecular weight which measured by the gel solvent permeation chromatography (GPC) with the chloroform solvent, and was calculated by the polymethylmethacrylate (PMMA) conversion method.

  By setting the weight average molecular weight of the polylactic acid resin to 50,000 or more, the mechanical properties of the polylactic acid resin sheet of the present invention containing the polylactic acid resin can be improved. The mechanical properties of a processed product made of a polylactic acid resin sheet can also be made excellent.

  Further, the polylactic acid resin used in the present invention may be a copolymerized polylactic acid resin obtained by copolymerizing other monomer components having ester forming ability in addition to L-lactic acid and D-lactic acid. 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 the polylactic acid resin.

  The method for producing the polylactic acid-based resin will be described later in detail, and examples thereof include a direct polymerization method from lactic acid and a ring-opening polymerization method via lactide.

When the polylactic acid resin sheet of the present invention does not require biodegradability, such as packaging for various industrial products, or when it is preferable to have storage durability, the strength is reduced due to hydrolysis of the polylactic acid resin. From the standpoint of suppressing the above and imparting good durability, the carboxyl group terminal concentration in the polylactic acid-based resin is preferably 0 equivalent / 10 ³ kg or more and 30 equivalent / 10 ³ kg or less, more preferably 20 equivalents. / 10 ³ kg or less, more preferably 10 equivalents / 10 ³ kg or less. When the carboxyl group terminal concentration in the polylactic acid-based resin is 30 equivalents / 10 ³ kg or less, the carboxyl group terminal concentration, which also serves as a hydrolysis autocatalyst, is sufficiently low. In many cases, sex can be imparted.

Examples of the method for setting the carboxyl group terminal concentration in the polylactic acid-based resin to 30 equivalents / 10 ³ kg or less include, for example, a method of controlling by the catalyst and thermal history during the synthesis of the polylactic acid-based resin, and the extrusion temperature at the time of forming the sheet And a method of reducing the thermal history such as reducing the retention time or shortening the residence time, a method of blocking the carboxyl group terminal using a reactive compound, and the like.

  In the method of blocking the carboxyl group terminal using a reactive compound, it is preferable that at least a part of the carboxyl group terminal in the polylactic acid resin is blocked, and it is more preferable that the whole amount is blocked. Examples of reactive compounds include condensation reactive compounds such as aliphatic alcohols and amide compounds, and addition reactive compounds such as carbodiimide compounds, epoxy compounds, and oxazoline compounds, but extra by-products are generated during the reaction. An addition reaction type compound is preferable in terms of difficulty, and a carbodiimide compound is particularly preferable from the viewpoint of reaction efficiency.

  For the purpose of improving the heat resistance of the polylactic acid resin sheet of the present invention, a resin having a glass transition temperature higher than that of the polylactic acid resin may be mixed. For example, poly (meth) acrylate resins, polyacetals, polyamides, polyphenylene sulfide resins, polyether ketone resins, polyesters, polysulfones, polyphenylene oxides, polyimides, polyether imides, polyvinyl compounds, and other thermoplastic resins, phenol resins, melamine resins, Examples thereof include thermosetting resins such as polyester resins, silicone resins, and epoxy resins.

  As the resin having a glass transition temperature higher than that of the polylactic acid-based resin used in the present invention, a poly (meth) acrylate-based resin is preferable because it has a suitable dispersibility in the polylactic acid-based resin. Although there is a concern about a decrease in impact resistance by mixing a poly (meth) acrylate resin, practical impact resistance can be maintained by mixing an impact modifier described later. A rubber component is a preferred example of the impact modifier that is mixed at the same time when the poly (meth) acrylate resin is mixed.

  The polylactic acid-based resin sheet of the present invention is a known antioxidant, UV stabilizer, anti-coloring agent, matting agent, deodorant, flame retardant, weathering agent, anti-resistance, and the like within a range that does not impair the effects of the present invention. As the oxidizing agent, ion exchange agent, crystal nucleating agent, coloring pigment, or the like, or as a lubricant, inorganic fine particles, organic particles, or an organic lubricant may be added as necessary.

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, and quinocridone. Organic pigments such as thioindigo can be used.

  In addition, when adding particles for the purpose of improving the slipperiness and blocking resistance of processed products, for example, as inorganic particles, various kinds of silicon oxide such as silica, calcium carbonate, magnesium carbonate, barium carbonate, etc. Various sulfates such as carbonate, calcium sulfate and barium sulfate, various composite oxides such as kaolin and talc, various phosphates such as lithium phosphate, calcium phosphate and magnesium phosphate, aluminum oxide, titanium oxide, zirconium oxide, etc. Fine particles composed of various oxides, 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 3 μm, and most preferably 0.08 to 2 μm.

  For the purpose of improving impact resistance, the polylactic acid resin sheet of the present invention may contain 2% by mass or more and 20% by mass or less of an impact resistance improver in 100% by mass of the entire sheet. Preferably they are 2.5 mass% or more and 15 mass% or less. As the content of the impact resistance improving agent increases, the impact resistance improving effect is improved. However, even if the content exceeds 20% by mass, a significant improvement in the impact resistance improving effect is often not obtained. .

  In addition, the impact resistance improving agent mentioned here means an additive having an effect of improving the brittleness characteristic that the polylactic acid resin originally has, which is brittle and easily cracked. In order to exert such an effect, when added to and mixed with a polylactic acid resin, the polylactic acid resin has a sea-island structure in which the additive is an island and the additive is usually an island. Examples thereof include an additive having a structure dispersed in a size that can be accommodated in a sphere having a diameter of about 10 μm. In this case, it is effective to select a so-called soft additive having a lower elastic modulus than the polylactic acid resin.

  Specific examples of such impact modifiers include, for example, ethylene-propylene copolymers, ethylene / propylene-nonconjugated diene copolymers, ethylene-1-butene copolymers, ethylene-acrylic acid copolymers, and Its alkali metal salt (so-called ionomer), ethylene-glycidyl (meth) acrylate copolymer, ethylene-alkyl acrylate copolymer (for example, ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer) , Acid-modified ethylene-propylene copolymer, diene rubber (eg, polybutadiene, polyisoprene, polychloroprene), copolymer of diene and vinyl monomer (eg, styrene-butadiene random copolymer, styrene-butadiene block copolymer) Coalescence, styrene-butadiene-styrene broth Copolymer, styrene-isoprene random copolymer, styrene-isoprene block copolymer, styrene-isoprene-styrene block copolymer, butadiene-grafted 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, epichlorohydride Rubber, aliphatic polyester, polyester elastomer and polyamide elastomer.

  Furthermore, those having various cross-linking degrees, those having various microstructures such as cis structure and trans structure, and multilayered polymers composed of a core layer and one or more shell layers covering the core layer are used. Can do.

  As the impact resistance improver used in the present invention, aliphatic polyesters other than polylactic acid resins are preferable in that they have suitable dispersibility in polylactic acid resins and a higher effect can be obtained with a small amount. And aliphatic aromatic polyesters are preferred.

  Aliphatic polyesters and aliphatic aromatic polyesters other than polylactic acid-based resins are not particularly limited, and specifically, polyglycolic acid, poly-3-hydroxybutyric acid, poly-4-hydroxybutyric acid, poly-4- Examples include hydroxyvaleric acid, poly-3-hydroxyhexanoic acid or polycaprolactone, polyethylene adipate, polyethylene succinate, polybutylene succinate, polybutylene succinate adipate, and the like.

  Furthermore, in order to improve impact resistance and maintain the biodegradability of the polylactic acid resin sheet, it is preferable to use a polybutylene succinate resin which is an aliphatic polyester other than the polylactic acid resin. More preferred are polybutylene succinate and polybutylene succinate adipate, which have a large impact resistance improving effect and are compatible with the polylactic acid resin.

  The weight average molecular weight of the polybutylene succinate resin used in the present invention is preferably 100,000 to 300,000. Examples of these polybutylene succinate resins include “GsPla” FZ71PD (trade name, product number; Mitsubishi Chemical) and Bionore # 3003 (trade name, product number; Showa Polymer). For example, polybutylene succinate is 1 Obtained by polycondensation of -4 butanediol and succinic acid.

  As the impact resistance improver used in the present invention, a multilayer structure polymer is also given as a preferred example in that it has suitable dispersibility in a polylactic acid resin and a higher effect can be obtained with a small amount. It is done.

  The multilayer structure polymer is composed of an innermost layer (core layer) and one or more layers (shell layer) covering the innermost layer (core layer), and a polymer having a structure in which adjacent layers are composed of different types of polymers. is there. The number of layers constituting the multilayer structure polymer is not particularly limited, and may be two or more layers, and may be three or more layers or four or more layers. The multilayer polymer preferably has at least one rubber layer inside. The type of the rubber layer is not particularly limited as long as it is composed of a polymer component having rubber elasticity. In addition, from the viewpoint that impact resistance can be improved while maintaining transparency even though it is not biodegradable, the multilayer structure polymer contained as an impact resistance improver is a core-shell type acrylic polymer. Is preferred.

  More specifically, examples of the type of the rubber layer include rubbers formed by polymerizing an acrylic component, a silicone component, a styrene component, a nitrile component, a conjugated diene component, a urethane component, an ethylene propylene component, or the like. Examples of the polymer component preferably used as the rubber layer include acrylic components such as ethyl acrylate units and butyl acrylate units, silicone components such as dimethylsiloxane units and phenylmethylsiloxane units, styrene units and α-methylstyrene units. The rubber is composed of a polymer obtained by polymerizing a styrene component, a nitrile component such as an acrylonitrile unit or a methacrylonitrile unit, or a conjugated diene component such as a butadiene unit or an isoprene unit. A rubber composed of a copolymer obtained by combining two or more of these components is also preferable. For example, (1) acrylic components such as ethyl acrylate units and butyl acrylate units, dimethylsiloxane units, and phenylmethylsiloxane Rubber composed of components copolymerized with silicone components such as units, (2) Components copolymerized with acrylic components such as ethyl acrylate units and butyl acrylate units, and styrene components such as styrene units and α-methylstyrene units (3) rubber composed of a component obtained by copolymerizing an acrylic component such as an ethyl acrylate unit or a butyl acrylate unit and a conjugated diene component such as a butadiene unit or an isoprene unit, and (4) ethyl acrylate. Acrylic components such as units and butyl acrylate units and di Rubber composed of a silicone component and component obtained by copolymerizing a styrene component such as styrene units or α- methylstyrene units such as chill siloxane units and phenyl methyl siloxane units and the like. In addition to these components, a rubber obtained by copolymerizing and crosslinking a crosslinkable component such as a divinylbenzene unit, an allyl acrylate unit, or a butylene glycol diacrylate unit is also preferable.

  A preferred example of the multilayer structure polymer is a multilayer structure polymer composed of a core layer and one shell layer, the core layer is a dimethylsiloxane / butyl acrylate polymer, and the outermost layer is a methyl methacrylate polymer. The core layer is a butadiene / styrene polymer, the outermost layer is a methyl methacrylate polymer, the core layer is a butyl acrylate polymer, and the outermost layer is a methyl methacrylate polymer. Furthermore, it is more preferable that either one or both of the rubber layer and the outermost layer is a polymer containing glycidyl methacrylate units.

  The melt kneading method of the polylactic acid resin and the impact resistance improver is not particularly limited, and a commonly used mixer such as a kneader, roll mill, Banbury mixer, single screw or twin screw extruder may be used. it can. 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 method of subjecting a polylactic acid resin and an impact modifier to dry blending and then supplying to a melt kneader, or a polylactic acid resin and an impact modifier previously melt kneaded. Examples thereof include a method of melt-kneading the master batch and the polylactic acid resin after producing the master batch. In addition, if necessary, a method in which other components are melt-kneaded at the same time, or a master batch in which a polylactic acid resin and other additives are melt-kneaded in advance are prepared, and then the master batch and the polylactic acid resin are melt-kneaded A method may be used.

  The polylactic acid resin in 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.

  The polylactic acid resin 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.

  The cutter made of the polylactic acid resin sheet of the present invention is preferably used as a cutter for cutting paper or film. It is particularly suitable for a film cutter, and can be easily cut not only for polyvinylidene chloride films but also for stretched or unstretched films such as polyethylene.

  The cutter of the present invention can be formed by punching a sheet, and the shape of the blade formed by punching is preferably a saw blade shape, and is preferably an acute blade. The tip angle of the blade, the size, length, and shape of the blade are not particularly limited.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited thereto.
[Measurement and evaluation method]
Measurements and evaluations shown in the examples were performed under the following conditions.

(1) Warpage amount Rh
A polylactic acid resin sheet was cut to a size of 300 mm in width (perpendicular to the film forming direction) and 8.5 mm in length (parallel to the film forming direction), and a hot air oven set at 80 ° C. (GPHH manufactured by Tabay Espec Corp.) -200), the amount of sheet warpage after standing for 1 hour was measured using a caliper.

  For the measurement of the amount of warpage, three samples per level were put in an oven, the maximum value of the amount of warpage of each sample was determined, and the average of the maximum values of the three samples was defined as the amount of warpage Rh.

The amount of warping refers to the maximum value of the amount of lifting from the four-sided plane when the concave sheet is placed on a flat surface with the central dent down and the lifted ends facing upward. The measurement position of the sheet for the amount of warpage was the lower side portion of the sheet in the thickness direction (the side of the sheet and the lower side in the thickness direction (plane side)).
(2) Cutability Sheets obtained in Examples and Comparative Examples are punched into a saw blade shape by punching, and a commercially available wrap film paper container for food packaging ((A): wrap film made of polyvinylidene chloride, width 300 mm, length 50m, (B): polyethylene wrap film, width 300mm, length 50m), the film cutter attached was replaced with the cutter of the present invention, and the paper container was allowed to stand in a thermostat set at 80 ° C for 1 hour. . Then, each was loaded with a wrap film, the wrap film was pulled out from the paper container by 300 mm, and the cutting with the replaced cutter was repeated 10 times to evaluate the cut performance.
○: Easily cut Δ: Cuttable ×: Not cutable (3) Sheet thickness The thickness was measured at 10 points with a micro gauge with respect to the full width of the sheet, and the average value t (μm) of the thickness was obtained to obtain the sheet thickness. .
(4) Centerline average roughness: Ra
Two-dimensional centerline average roughness (Ra) was measured with a universal surface shape measuring instrument SE-3FA (manufactured by Kosaka Laboratory Ltd.). Measurement conditions are a stylus tip radius: 2 μm, a measurement force: 0.7 mN, a measurement length of 25 mm, and a cut-off: 0.08 mm.
(5) Coefficient of dynamic friction: μd
According to JIS-K-7125 (1999), a slip tester (manufactured by Toyo Tester Kogyo Co., Ltd.) was used and the load was 200 g. The value was calculated using the following formula. The combination of different surfaces means that two sheet samples are prepared and overlapped so that the Ra1 surface of one sample and the Ra2 surface of the other sample are in contact with each other.
Coefficient of dynamic friction: μd = resistance value / load (6) Sheet appearance The appearance of the obtained sheet was visually observed and evaluated according to the following criteria.
○: The sheet is smooth and practical without any problem in flatness.
X: The sheet is not smooth, and there is a problem in flatness, so that it is not practical.
[Polylactic acid resin used]
(PLA-1):
A poly L-lactic acid resin having a poly D-lactic acid content of 5.0 mol%, a melting point of 150 ° C., and a weight average molecular weight of 220,000 in terms of PMMA. (4042D from NATure Works)
[Poly (meth) acrylate resin]
(PMMA-1):
Polymethylmethacrylate (“SUMIPEX” HT50Y manufactured by Sumitomo Chemical)
[Used inorganic particle masterbatch]
(MB-1):
Titanium oxide (25% by mass in 100% by mass of masterbatch), ethylenebisstearyl acid (2% by mass in 100% by mass of masterbatch), PLA-1 (73% in 100% by mass of masterbatch) based master chip (titanium oxide) (Average particle size: 0.2 μm)
[Preparation of polylactic acid resin sheet]
Example 1
Using two bent twin-screw extruders, polylactic acid resin and inorganic particles so that the sheet has three layers of layer A / layer B / layer A (thickness ratio of each layer: 1/8/1) The master batch is supplied to two vent type twin screw extruders for layer A and layer B at the ratios shown in Table 1, extruded from a T die die with a die temperature set at 210 ° C., and rotated in a direction in contact with each other. Then, the sheet was nipped between the cooling rolls R0 and R1, and subsequently taken into close contact with the cooling roll R1, cooled and solidified into a sheet, and an unstretched sheet having a thickness of 250 μm was prepared.

At that time, the surface temperature T ₀ of the cooling roll R0 is 30 ° C., the surface temperature T ₁ of the cooling roll R1 is 40 ° C., the rotational speed V ₀ of the cooling roll R0 is 15.8 m / min, and the rotational speed V of the cooling roll R1. ₁ was 15.0 m / min.

The evaluation results of the obtained sheet are shown in Table 1.
(Examples 2-6, Comparative Examples 1-4)
In the same manner as in Example 1, the raw materials were changed to the composition ratios shown in Table 1, and the rotational speeds and surface temperatures of the cooling rolls R0 and R1 were prepared under the conditions shown in Table 1, respectively.

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

  The sheets produced in Examples 1 to 6 were excellent in cutability, and Example 4 was particularly excellent. On the other hand, all the sheets produced in Comparative Examples 1 to 4 have difficulty in cutting and sheet flatness, and lack practicality.

Claims (6)

An unstretched sheet mainly composed of a polylactic acid-based resin,
A polylactic acid resin sheet characterized in that a sheet curl amount Rh (mm) when treated at 80 ° C. for 1 hour satisfies the following conditions.
Rh ≦ 2 The thickness is 150 μm or more,
When the two-dimensional centerline average roughness of one surface of the sheet is Ra1 (μm) and the two-dimensional centerline average roughness of the other surface is Ra2 (μm), the following conditions are satisfied: Item 10. A polylactic acid resin sheet according to Item 1.
0.005 ≦ | Ra1-Ra2 | ≦ 0.2
(However, the surfaces of Ra1 and Ra2 are selected so that Ra1 <Ra2.)   A cutter comprising the polylactic acid resin sheet according to claim 1. In the sheet manufacturing method including a step of niping the sheet-like molten polymer with a pair of cooling rolls (R0 and R1), and subsequently drawing the molten polymer in close contact with the cooling roll R1,
Rotation speed V ₀ which cooling roll R0 _(m / min), and the rotation speed V ₁ of the cooling roll R1 _(m / min), polylactic acid-based resin sheet manufacturing method, wherein the following condition is satisfied.
1.03V ₁ ≦ V ₀ ≦ 1.15V ₁ The rotation speed V ₀ is, polylactic acid resin sheet manufacturing method according to claim 4, wherein the following condition is satisfied.
12 m / min ≦ V ₀ ≦ 40 m / min The surface temperature T ₀ of the cooling roll R0 _(° C.), and the surface temperature T ₁ of the cooling roll R1 _(° C.) is a polylactic acid-based resin sheet according to claim 4 or 5, wherein the following condition is satisfied Production method.
20 ≦ T ₀ , T ₀ + 3 ≦ T ₁ ≦ 45