JP5883307B2 - Protective film - Google Patents

Description

  The present invention relates to a protective film (including a sheet), more specifically, a polylactic acid film or sheet that is excellent in heat resistance, excellent in tear resistance, and does not break or tear during manufacturing or processing. It relates to a protective film. This protective film is a protective film for protecting the surface of an automobile wheel; a protective film for protecting the surface of an optical member or electronic component such as a polarizing plate, a wave plate, a retardation plate, a reflective sheet, etc. used in a liquid crystal display or the like. Film: It can be used for a protective film for protecting the surface of a metal layer or a metal oxide layer used for a plasma display panel, an electromagnetic shielding material for CRT, or the like. The protective film is peeled off and removed when it is no longer needed.

  Polylactic acid is a plant-derived biomass polymer and has attracted attention as a resin that replaces petroleum-derived polymers. Polylactic acid is a high-elasticity, high-strength polymer, but has poor toughness and low impact resistance, tear resistance, and flexibility. In addition, since the crystallization speed is slow, almost no crystal growth occurs in normal crystal growth, and although the melting point is about 170 ° C., thermal deformation occurs at a temperature of 60 ° C. or higher of the glass transition temperature, and the film shape is changed. Inability to hold is also an important issue. Therefore, several methods have been proposed in the past in order to improve the heat resistance of the polylactic acid resin film.

  As a countermeasure against these problems, a method has been proposed in which polylactic acid is improved by blending a soft and heat-resistant polymer (Patent Document 1). In addition, a method has been proposed in which aliphatic polyester / core-shell type rubber is added to polylactic acid and uniaxially or biaxially stretched (Patent Document 2). Either method can achieve both impact resistance and heat resistance, but since a large amount of petroleum-derived polymers and additives are blended, there is a problem that the ratio of plant-derived components (biomass degree) is significantly reduced. there were.

  Also, as a technique for imparting flexibility and heat resistance to a polylactic acid film, a resin composition containing polylactic acid, a plasticizer, and a crystal nucleating agent is promoted in a heat treatment step provided after film formation. Has been proposed (Patent Document 3). However, this method has a problem that bleeding out may occur due to the addition of a plasticizer, and an improvement effect on flexibility is obtained, but an improvement effect on tear resistance is poor.

JP 2006-70224 A JP 2009-173715 A Japanese Patent No. 4699180

  Accordingly, the object of the present invention is to have a tear strength that does not cause breakage or tearing during the production or processing of the protective film, when it is wound into a roll, etc., and it can be melted or deformed even at a high temperature exceeding 100 ° C. It is providing the protective film which uses a polylactic acid-type film or sheet | seat without a base as a base material.

  As a result of intensive studies to achieve the above object, the present inventors have a tear strength of a certain value or more as a substrate, and a heating dimensional change rate (%) and a heating load dimensional change rate (%). It has been found that the above-mentioned problems can be solved by using a polylactic acid resin film or sheet that is within a certain value, and the present invention has been completed.

That is, the present invention
A protective film having a releasable pressure-sensitive adhesive layer on at least one surface of a substrate,
The substrate is
Containing polylactic acid (A),
The tear strength (JIS K7128-3 Plastics-Test method for tear strength of films and sheets-Part 3: Conforms to the right-angled tear method) is at least 100 N / mm when tearing in the flow direction (MD direction) ,
The following formula (1) when stored for 1 minute in an atmosphere of 100 ° C.
Heating dimensional change rate (%) = (L2−L1) / L1 × 100 (1)
(In the formula, L1 indicates the length of the marked line before the test, L2 indicates the length of the marked line after the test), and the heating dimensional change rate is ± in both the flow direction (MD direction) and the width direction (TD direction). The following formula (2) when the load is 300 g per 1 mm ² in the flow direction (MD direction) and stored for 1 minute in an atmosphere of 3% or less and 100 ° C.
Heating load dimensional change rate (%) = (L4−L3) / L3 × 100 (2)
(Wherein L3 is the length of the marked line before the test and L4 is the length of the marked line after the test), the dimensional change rate of the heating load is within ± 3% in the flow direction (MD direction).
A protective film comprising a polylactic acid film or sheet is provided.

  The polylactic acid film or sheet constituting the substrate may further contain a modifier (E). In addition, the polylactic acid film or sheet constituting the substrate is (a) a polyglycerol fatty acid ester and / or a polyglycerol condensed hydroxy fatty acid ester as the modifier (E) with respect to the polylactic acid (A). The weight ratio of polylactic acid (A) to (a) polyglycerol fatty acid ester and / or polyglycerol condensed hydroxy fatty acid ester is 99: 1 to 80:20 (the former: the latter (total amount of (a))). You may contain.

  The polylactic acid film or sheet constituting the base material is a core-shell structure polymer having a graft layer on the outside of (b) particulate rubber as the modifier (E) with respect to the polylactic acid (A). Is contained so that the weight ratio of polylactic acid (A) and (b) core-shell structure polymer having a graft layer outside the particulate rubber is 99: 1 to 80:20 (the former: the latter). May be.

  The polylactic acid film or sheet constituting the substrate is composed of (c) a soft aliphatic polyester as the modifier (E), polylactic acid (A) and (c), relative to the polylactic acid (A). ) You may contain so that a weight ratio with soft aliphatic polyester may be 95: 5-60: 40 (the former: the latter).

  The polylactic acid-based film or sheet constituting the substrate further comprises polylactic acid (A) (however, when the modifying agent (E) is included, it comprises polylactic acid (A) and modifying agent (E). Composition) Even if it contains 0.1 to 10 parts by weight of an acidic functional group-modified olefin polymer (B) having an acid value of 10 to 70 mgKOH / g and a weight average molecular weight of 10,000 to 80,000 based on 100 parts by weight. Good. The acidic functional group of the acidic functional group-modified olefin polymer (B) may be an acid anhydride group.

  The polylactic acid-based film or sheet constituting the substrate further comprises polylactic acid (A) (however, when the modifying agent (E) is included, it comprises polylactic acid (A) and modifying agent (E). The composition may contain 0.5 to 15 parts by weight of the fluoropolymer (C) with respect to 100 parts by weight. The fluoropolymer (C) may be a tetrafluoroethylene polymer.

  The polylactic acid-based film or sheet constituting the substrate further comprises polylactic acid (A) (however, when the modifying agent (E) is included, it comprises polylactic acid (A) and modifying agent (E). The composition may contain 0.1 to 15 parts by weight of the crystallization accelerator (D) with respect to 100 parts by weight.

  The polylactic acid film or sheet constituting the substrate may be a film or sheet formed by a melt film formation method, for example, a calendar method.

The present invention also provides:
A method for producing a protective film, which is based on a polylactic acid film or sheet obtained by forming a resin composition containing polylactic acid (A) using a melt film formation method,
A melt film-forming step of melt-forming a resin composition;
After the melt film-forming step, the resin composition is cooled and solidified to obtain a film or sheet;
After the cooling and solidifying step, the film or sheet is heated, and has a crystallization promoting step for promoting crystallization of the film or sheet,
The resin temperature in the melt film formation step is within the range of the melting temperature (Tm) -15 ° C. to (Tm) + 15 ° C. in the temperature rising process of the resin composition,
In at least a part of the crystallization promoting step, crystallization of the film or sheet is promoted within a temperature range of crystallization temperature (Tc) + 10 ° C. to (Tc) + 50 ° C. in the temperature rising process of the resin composition. A method for producing a protective film is provided.

The production method of the protective film is as follows:
A residual stress relaxation step after the melt film formation step and before the cooling and solidification step;
In the residual stress relaxation step, the resin composition may be held within a temperature range of (Tm) -70 ° C to (Tm) -20 ° C.

  The resin composition may further contain a modifier (E).

  The resin composition comprises (a) a polyglycerin fatty acid ester and / or a polyglycerin condensed hydroxy fatty acid ester as the modifier (E) with respect to the polylactic acid (A). ) The polyglycerin fatty acid ester and / or the polyglycerin condensed hydroxy fatty acid ester may be contained in a weight ratio of 99: 1 to 80:20 (the former: the latter (total amount of (a))).

  The resin composition comprises, as the modifier (E), (b) a core-shell structure polymer having a graft layer outside the particulate rubber as the modifier (E) and polylactic acid (A). (B) You may contain so that the weight ratio with the core-shell structure polymer which has a graft layer on the exterior of particulate rubber may become 99: 1-80: 20 (the former: the latter).

  The resin composition comprises (c) a soft aliphatic polyester as the modifier (E), and polylactic acid (A) and (c) a soft aliphatic polyester. You may contain so that a weight ratio may be 95: 5-60: 40 (the former: the latter).

  The resin composition is further added to 100 parts by weight of polylactic acid (A) (however, when the modifying agent (E) is included, the composition comprising polylactic acid (A) and modifying agent (E)). The acid functional group-modified olefin polymer (B) having an acid value of 10 to 70 mgKOH / g and a weight average molecular weight of 10,000 to 80,000 may be contained in an amount of 0.1 to 10 parts by weight. The acidic functional group of the acidic functional group-modified olefin polymer (B) may be an acid anhydride group.

  The resin composition is further added to 100 parts by weight of polylactic acid (A) (however, when the modifying agent (E) is included, the composition comprising polylactic acid (A) and modifying agent (E)). The fluorine-based polymer (C) may contain 0.5 to 15 parts by weight. The fluoropolymer (C) may be a tetrafluoroethylene polymer.

  The resin composition is further added to 100 parts by weight of polylactic acid (A) (however, when the modifying agent (E) is included, the composition comprising polylactic acid (A) and modifying agent (E)). The crystallization accelerator (D) may be contained in an amount of 0.1 to 15 parts by weight.

  The melt film forming method may be a calendar method.

  The protective film of the present invention does not melt or deform the base material even at a high temperature exceeding 100 ° C., and maintains the original rigidity of the base material, and is wound in a roll shape during the production or processing of the protective film. In this case, even if tension is applied, it has a characteristic that it does not break or tear. Furthermore, it is possible to prevent breakage or tearing when the protective film is reattached or finally peeled off.

It is a schematic diagram which shows an example of the calendering machine used when manufacturing the base material (polylactic acid-type film or sheet | seat) of the protective film of this invention. It is a schematic diagram which shows an example of the polishing film-forming machine used when manufacturing the base material (polylactic acid-type film or sheet | seat) of the protective film of this invention.

[Base material]
The polylactic acid film or sheet used as the base material of the protective film of the present invention is a resin film or sheet containing polylactic acid (A). Since lactic acid, which is a raw material monomer for polylactic acid, has an asymmetric carbon atom, there are L and D isomers of optical isomers. The polylactic acid (A) used in the present invention is a polymer mainly composed of L-form lactic acid. The smaller the content of lactic acid in the D-form that is mixed as an impurity during production, the higher the crystallinity and the higher melting point of the polymer. Therefore, it is preferable to use the L-form purity as high as possible, and the L-form purity is 95%. It is more preferable to use the above. Moreover, polylactic acid (A) may contain other copolymerization components other than lactic acid.

  Examples of the other copolymer components include ethylene glycol, propylene glycol, 1,3-propanediol, butanediol, pentanediol, neopentylglycol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, 1 , 4-cyclohexanedimethanol, glycerin, pentaerythritol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, bisphenol A and other polyol compounds; oxalic acid, malonic acid, glutaric acid, adipic acid, sebacic acid, azelaic acid, dodecanedione Acid, cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, bis (p-carboxyphenyl) methane, anthracene Polycarboxylic acids such as carboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 5-sodium sulfoisophthalic acid, 5-tetrabutylphosphonium isophthalic acid; glycolic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid And hydroxycarboxylic acids such as hydroxybenzoic acid; lactones such as propiolactone, valerolactone, caprolactone, undecalactone, and 1,5-oxepan-2-one. These copolymerization components are preferably 0 to 30 mol%, more preferably 0 to 10 mol%, based on all monomer components constituting the polylactic acid (A).

  The weight average molecular weight of polylactic acid (A) is, for example, 10,000 to 400,000, preferably 50,000 to 300,000, and more preferably 80,000 to 200,000. Moreover, the melt flow rate [JIS K-7210 (test condition 4)] of polylactic acid (A) at 190 ° C. and a load of 21.2 N is, for example, 0.1 to 50 g / 10 minutes, preferably 0.2 to 20 g. / 10 minutes, more preferably 0.5 to 10 g / 10 minutes, and particularly preferably 1 to 7 g / 10 minutes. If the melt flow rate is too high, the mechanical properties and heat resistance of the film or sheet obtained by film formation may be inferior. On the other hand, if the value of the melt flow rate is too low, the load during film formation may become too high.

In the present invention, “weight average molecular weight” refers to that measured by gel permeation chromatography (GPC) (in terms of polystyrene). The measurement conditions of GPC are as follows.
Column: TSKgel SuperHZM-H / HZ2000 / HZ1000
Column size: 4.6 mm I.D. D. × 150mm
Eluent: Chloroform Flow rate: 0.3 ml / min
Detector: RI
Column temperature: 40 ° C
Injection volume: 10 μl

  The production method of polylactic acid is not particularly limited, but typical production methods include lactide method and direct polymerization method. In the lactide method, lactic acid is heated and dehydrated and condensed to give low molecular weight polylactic acid, which is then thermally decomposed under reduced pressure to obtain lactide, which is a cyclic dimer of lactic acid, and this lactide is converted into tin (II) octanoate or the like. In this method, high molecular weight polylactic acid is obtained by ring-opening polymerization in the presence of a metal salt catalyst. The direct polymerization method is a method in which polylactic acid is directly obtained by heating lactic acid in a solvent such as diphenyl ether under reduced pressure and polymerizing it while removing water in order to suppress hydrolysis.

  A commercially available product can be used as the polylactic acid (A). Commercially available products include, for example, trade names “LAISIA H-400”, “LAISIA H-100” (manufactured by Mitsui Chemicals), trade names “TERRAMAC TP-4000”, “TERRAMAC TE-4000” (above, Unitika Ltd.) Manufactured) and the like. Of course, as polylactic acid (A), you may use what was manufactured by the well-known thru | or usual polymerization method (for example, emulsion polymerization method, solution polymerization method, etc.).

  The content of polylactic acid (A) in the polylactic acid film or sheet is usually 60% by weight or more, preferably 70% by weight or more, more preferably 80% by weight or more, particularly preferably, from the viewpoint of increasing the degree of biomass. Is 85% by weight or more. Moreover, the upper limit of content of the said polylactic acid (A) is 97 weight%, for example, Preferably it is 95 weight%, More preferably, it is 93 weight%. Here, the biomass degree is the ratio of the dry weight of the used biomass to the dry weight of the film or sheet. Biomass is a renewable, organic organic resource that excludes fossil resources.

  In the present invention, the polylactic acid film or sheet constituting the substrate may contain an acidic functional group-modified olefin polymer (B). By blending the acidic functional group-modified olefin polymer (B) with the polylactic acid (A), roll lubricity can be imparted. For this reason, when a polylactic acid film or sheet is melted by a calender film forming machine or the like and formed into a film by passing through a gap between the metal rolls, the film or sheet is easily peeled off from the surface of the metal roll, and smooth. It can be formed into a film. The acidic functional group-modified olefin polymer (B) can be used alone or in combination of two or more.

  Examples of the acidic functional group of the acidic functional group-modified olefin polymer (B) include a carboxyl group or a derivative group thereof. The derivative group of a carboxyl group is chemically derived from a carboxyl group, and examples thereof include an acid anhydride group, an ester group, an amide group, an imide group, and a cyano group. Among these, an anhydride group is preferable, and a carboxylic acid anhydride group is more preferable.

  The acidic functional group-modified olefin polymer (B) is abbreviated as, for example, an unsaturated compound containing the above “acidic functional group” (hereinafter referred to as “acidic functional group-containing unsaturated compound”) in an unmodified polyolefin polymer. In some cases).

  Examples of the unmodified polyolefin polymer include high density polyethylene, medium density polyethylene, low density polyethylene, polypropylene, polybutene, poly-4-methylpentene-1, a copolymer of ethylene and α-olefin, and propylene and α-olefin. Polyolefins such as copolymers or oligomers thereof; ethylene-propylene rubber, ethylene-propylene-diene copolymer rubber, butyl rubber, butadiene rubber, low crystalline ethylene-propylene copolymer, propylene-butene copolymer, Polyolefin such as ethylene-vinyl ester copolymer, ethylene-methyl (meth) acrylate copolymer, ethylene-ethyl (meth) acrylate copolymer, ethylene-maleic anhydride copolymer, blend of polypropylene and ethylene-propylene rubber Series Lastmers; and mixtures of two or more of these. Among these, preferred are polypropylene, a copolymer of propylene and α-olefin, low density polyethylene and oligomers thereof, and particularly preferred is a copolymer of polypropylene, propylene and α-olefin and oligomers thereof. It is. Examples of the “oligomers” include those obtained from a corresponding polymer by a molecular weight degradation method by thermal decomposition. Oligomers can also be obtained by polymerization methods.

  Examples of the acidic functional group-containing unsaturated compound include a carboxyl group-containing unsaturated compound and a carboxyl group derivative-containing unsaturated compound. Examples of the carboxyl group-containing unsaturated compound include maleic acid, itaconic acid, chloroitaconic acid, chloromaleic acid, citraconic acid, and (meth) acrylic acid. Examples of the carboxyl group derivative-containing unsaturated compound include, for example, maleic anhydride, itaconic anhydride, chloroitaconic anhydride, chloromaleic anhydride, citraconic anhydride and other carboxylic anhydride group-containing unsaturated compounds; (Meth) acrylate, glycidyl (meth) acrylate, (meth) acrylic acid ester such as 2-hydroxyethyl (meth) acrylate; (meth) acrylamide, maleimide, (meth) acrylonitrile and the like. Among these, a carboxyl group-containing unsaturated compound and a carboxylic acid anhydride group-containing unsaturated compound are preferable, an acid anhydride group-containing unsaturated compound is more preferable, and maleic anhydride is particularly preferable.

  It is important that the weight average molecular weight of the acidic functional group-modified olefin polymer (B) is 10000 to 80000, preferably 15000 to 70000, more preferably 20000 to 60000. If this weight average molecular weight is less than 10,000, it tends to cause bleed-out after film or sheet molding, and if it exceeds 80000, it may separate from polylactic acid (A) during roll kneading. Here, bleed-out refers to a phenomenon in which a low molecular weight component appears on the film or sheet surface over time after the film or sheet is formed.

  The acidic functional group in the acidic functional group-modified olefin polymer (B) may be bonded to any position of the olefin polymer, and the modification ratio is not particularly limited, but the acidic functional group-modified olefin polymer (B). The acid value of is usually 10 to 70 mgKOH / g, preferably 20 to 60 mgKOH / g. If the acid value is less than 10 mgKOH / g, the effect of improving roll lubricity cannot be obtained, and if it exceeds 70 mgKOH / g, it tends to cause plate-out to the roll. Here, the plate-out to the roll means that when the resin composition is melt-formed using a metal roll, the components blended in the resin composition or the oxidized, decomposed, combined, or deteriorated product is a metal. Attaching or depositing on the surface of a roll. In addition, in this invention, an "acid value" means what is measured based on the neutralization titration method of JISK0070-1992.

  The acidic functional group-modified olefin polymer (B) is obtained by reacting an unmodified polyolefin polymer with an acidic functional group-containing unsaturated compound in the presence of an organic peroxide. As the organic peroxide, those generally used as an initiator in radical polymerization can be used. Such a reaction can be performed by either a solution method or a melting method. In the solution method, an acidic functional group-modified olefin polymer (B) is obtained by dissolving a mixture of an unmodified polyolefin polymer and an acidic functional group-containing unsaturated compound in an organic solvent together with an organic peroxide and heating. Can do. The reaction temperature is preferably about 110 to 170 ° C.

  In the melting method, an acidic functional group-modified olefin polymer (B) is obtained by mixing a mixture of an unmodified polyolefin-based polymer and an acidic functional group-containing unsaturated compound with an organic peroxide, melt-mixing and reacting. be able to. Melt mixing can be performed with various mixers such as an extruder, a plastic bender, a kneader, and a Banbury mixer, and the kneading temperature is usually in the temperature range of the melting point to 300 ° C. of the unmodified polyolefin polymer.

  The acidic functional group-modified olefin polymer (B) is preferably maleic anhydride-modified polypropylene. As the acidic functional group-modified olefin polymer (B), commercially available products can be used. For example, trade name “Yumex 1010” (maleic anhydride group-modified polypropylene, acid value: 52 mgKOH / g, manufactured by Sanyo Chemical Industries, Ltd.) (Weight average molecular weight: 32000, modification ratio: 10% by weight), “Yumex 1001” (maleic anhydride group-modified polypropylene, acid value: 26 mg KOH / g, weight average molecular weight: 49000, modification ratio: 5% by weight), “Yumex 2000 (Maleic anhydride group-containing modified polyethylene, acid value: 30 mg KOH / g, weight average molecular weight: 20000, modification ratio: 5% by weight) and the like.

  The content of the acidic functional group-modified olefin polymer (B) in the polylactic acid film or sheet is not particularly limited. For example, polylactic acid (A) (provided that the modifier (E) is included, polylactic acid is included) (A) Composition comprising (A) and modifier (E)) Acid functional group-modified olefin polymer (B) having an acid value of 10 to 70 mgKOH / g and a weight average molecular weight of 10,000 to 80,000 per 100 parts by weight. 0.1 to 10 parts by weight may be contained, and from the viewpoint of sustaining the roll slip effect without plate-out to the roll and maintaining the degree of biomass, preferably 0.1 to 5 parts by weight, particularly preferably 0 .3 to 3 parts by weight. If the content of the acidic functional group-modified olefin polymer (B) is less than 0.1 parts by weight, the effect of improving roll lubricity is difficult to obtain, and if it exceeds 10 parts by weight, the effect according to the amount added cannot be obtained. In addition, a decrease in biomass degree becomes a problem.

  In the present invention, a fluorine-based polymer (C) may be used in addition to the above components in the polylactic acid film or sheet constituting the substrate. The fluorine-based polymer (C) is used, for example, as a melt tension adjusting agent or a crystallization accelerator. Examples of the fluorine-based polymer (C) include tetrafluoroethylene-based polymers, polychlorotrifluoroethylene, polyvinylidene fluoride, and polyvinyl fluoride. A fluorine-type polymer (C) can be used individually by 1 type or in combination of 2 or more types. As the fluoropolymer (C), a tetrafluoroethylene polymer (C ′) can be particularly preferably used.

  The tetrafluoroethylene-based polymer (C ′) may be a tetrafluoroethylene homopolymer or a copolymer of tetrafluoroethylene and another monomer. Examples of the tetrafluoroethylene-based polymer (C ′) include polytetrafluoroethylene, perfluoroalkoxyalkane (copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether), and perfluoroethylene propene copolymer (tetrafluoroethylene and hexafluoro). Copolymer with propylene), ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene-perfluorodioxole copolymer and the like. Among these, polytetrafluoroethylene is preferable. The tetrafluoroethylene-based polymer (C ′) can be used alone or in combination of two or more.

  When the fluorine-based polymer (C) is blended with the polylactic acid (A) -containing resin composition, the melt tension is improved and the melt viscosity is also increased. For example, when the film is formed using a calendar roll, the film is formed. It is possible to prevent the elongation and peeling failure when the resin composition leaves the roll. In particular, fluorine-based polymers such as tetrafluoroethylene-based polymer (C ′) also have a function as a crystal nucleating agent for polylactic acid (A), so that the temperature of the resin composition immediately after film formation is the crystallization temperature. By setting in the vicinity, crystallization of polylactic acid (A) can be further promoted. Thus, crystallization of polylactic acid (A) can be promoted by blending the fluorine-based polymer (C) [particularly, tetrafluoroethylene-based polymer (C ′)].

  The function of the tetrafluoroethylene polymer (C ′) as a crystal nucleating agent for the polylactic acid (A) is considered to depend on the crystal structure of the tetrafluoroethylene polymer (C ′). As a result of wide-angle X-ray diffraction, the plane spacing of the polylactic acid crystal lattice was 4.8 angstroms, whereas that of the tetrafluoroethylene polymer (C ′) was 4.9 angstroms. From this, it is considered that the tetrafluoroethylene-based polymer (C ′) can act as a crystal nucleating agent for the polylactic acid (A) by having an epitaxy action. Here, the epitaxy action means that polylactic acid (A) grows on the surface of the tetrafluoroethylene polymer (C ′) and aligns with the crystal plane of the crystal surface of the tetrafluoroethylene polymer (C ′). This refers to the growth pattern in which lactic acid (A) is arranged.

  The surface spacing of the tetrafluoroethylene-based polymer (C ′) is governed by the crystal form of the tetrafluoroethylene portion even if it is a copolymer of tetrafluoroethylene and other monomers. Is the same. Accordingly, the amount of the other monomer component of the copolymer is not particularly limited as long as the crystal form of polytetrafluoroethylene can be maintained and the physical properties are not greatly changed. Usually, the tetrafluoroethylene polymer (C The ratio of the other monomer component in ′) is desirably 5% by weight or less.

  The tetrafluoroethylene polymer (C ′) may be obtained by any polymerization method, but is preferably obtained by emulsion polymerization. Since the tetrafluoroethylene-based polymer obtained by emulsion polymerization is easy to fiberize, it becomes easy to take a network structure in polylactic acid (A), and improves the melt tension of the resin composition containing polylactic acid (A). It is considered to work effectively.

  Further, in order to uniformly disperse the polylactic acid (A), the particles of the tetrafluoroethylene polymer (C ′) are compatible with the polylactic acid (A) such as a (meth) acrylic acid ester polymer. You may use what modified | denatured with the polymer with favorable property. Examples of such tetrafluoroethylene-based polymer (C ′) include acrylic-modified polytetrafluoroethylene.

  The weight average molecular weight of the fluorine-based polymer (C) [tetrafluoroethylene-based polymer (C ′) etc.] is not particularly limited, but is usually 1 million to 10 million, preferably 2 million to 8 million.

  Commercial products may be used as the fluorine-based polymer (C) [tetrafluoroethylene-based polymer (C ′) etc.]. For example, as a commercial product of polytetrafluoroethylene, trade names “Fluon CD-014”, “Fluon CD-1”, “Fluon CD-145” manufactured by Asahi Glass Co., Ltd. and the like can be mentioned. Examples of commercially available products of acrylic-modified polytetrafluoroethylene include Metabrene A series such as trade names “Metabrene A-3000” and “Metabrene A-3800” manufactured by Mitsubishi Rayon Co., Ltd.

  The content of the fluorine-based polymer (C) in the polylactic acid-based film or sheet [particularly, the content of the tetrafluoroethylene-based polymer (C ′)] is not particularly limited, but for example, polylactic acid (A) (however, modified In the case where the quality agent (E) is contained, 0.5 to 15 parts by weight of the fluoropolymer (C) is contained with respect to 100 parts by weight of the polylactic acid (A) and the modifier (E). From the viewpoint of improving the melt tension and maintaining the degree of biomass, and obtaining a good surface state, it is preferably 0.7 to 10 parts by weight, more preferably 1 to 5 parts by weight. When the content of the fluoropolymer (C) [particularly, the content of the tetrafluoroethylene polymer (C ′)] is less than 0.5 parts by weight, the effect of improving the melt tension is difficult to obtain, and exceeds 15 parts by weight. And the effect according to addition amount is not acquired, and the fall of a biomass degree becomes a problem.

  The specific method for producing the polylactic acid type film or sheet is not particularly limited, but for example, (1) a resin composition containing polylactic acid (A) is formed using a melt film formation method such as a calender method. (2) Forming a resin composition in which a crystallization accelerator is blended with polylactic acid (A), and (3) a combination thereof. The melt film forming method will be described later.

  As the crystallization accelerator, those other than the fluorine-based polymer [for example, tetrafluoroethylene-based polymer (C ′), etc.] that can be used as the crystallization accelerator in the fluorine-based polymer (C) can be used. . Such a crystallization accelerator [may be referred to as crystallization accelerator (D)] is not particularly limited as long as an effect of promoting crystallization is recognized, but is a crystal lattice of polylactic acid (A). It is desirable to select a substance having a crystal structure having a face spacing close to the face spacing. This is because a substance having a crystal lattice spacing close to that of polylactic acid (A) is more effective as a crystal nucleating agent for polylactic acid (A). Examples of such a crystallization accelerator (D) include organic materials such as melamine polyphosphate, melamine cyanurate, zinc phenylphosphonate, calcium phenylphosphonate, magnesium phenylphosphonate, inorganic talc, clay. Etc. Of these, zinc phenylphosphonate is preferred because the face spacing is closest to the face spacing of polylactic acid (A), and a good crystallization promoting effect is obtained. The crystallization accelerator (D) can be used alone or in combination of two or more.

  A commercial item can be used as a crystallization promoter (D). For example, as a commercial product of zinc phenylphosphonate, a trade name “Eco Promote” manufactured by Nissan Chemical Co., Ltd. may be mentioned.

  The content of the crystallization accelerator (D) in the polylactic acid film or sheet is not particularly limited. For example, polylactic acid (A) (provided that the modifier (E) is included, polylactic acid (A) ) And a composition comprising the modifier (E)) 100 parts by weight, 0.1 to 15 parts by weight of the crystallization accelerator (D), from the viewpoint of better crystallization promotion effect and biomass degree maintenance, Preferably it is 0.3-10 weight part. When the content of the crystallization accelerator (D) is less than 0.1 parts by weight, the effect of promoting crystallization is difficult to obtain. When the content exceeds 15 parts by weight, the effect according to the amount added cannot be obtained. Decrease in biomass degree becomes a problem. As the fluoropolymer (C), a tetrafluoroethylene polymer (C ′) is replaced with polylactic acid (A) (provided that the modifier (E) contains polylactic acid (A) and the modifier (E When the composition is used at a ratio of 0.1 to 15 parts by weight with respect to 100 parts by weight, the content of the crystallization accelerator (D) is polylactic acid (A) (provided that the modifier (E ) Is contained in 100 parts by weight of the composition comprising polylactic acid (A) and modifier (E)), from the viewpoint of better crystallization promoting effect and maintaining the degree of biomass. 1 to 5 parts by weight, more preferably 0.3 to 3 parts by weight. In this case, if the content of the crystallization accelerator (D) is less than 0.1 parts by weight, the effect of promoting crystallization is difficult to obtain, and if it exceeds 5 parts by weight, the effect according to the amount added is obtained. In addition, a decrease in the degree of biomass becomes a problem.

  In the present invention, the polylactic acid-based film or sheet has a tear strength of 100 N / mm or more, preferably 150 N / mm or more when it is torn at least in the flow direction (MD direction). When a polylactic acid film or sheet having such tear strength is used as the base material of the protective film, even when the protective film is produced or when the protective film is processed, there is a step that takes tension, No breakage or tearing occurs. Further, even when wound into a roll shape or subjected to a punching process or the like, no breakage or tearing occurs. Furthermore, no breakage or tearing occurs when the protective film is re-applied or finally peeled off.

  In the present invention, the tear strength can be measured according to JIS K7128-3 Plastics-Tear Strength Test Method for Films and Sheets-Part 3: Right Angle Tear Method. A polylactic acid-based film or sheet having a tear strength of 100 N / mm or more when tearing at least in the flow direction (MD direction) is not only at the time of production of the film or sheet, but also in a roll-like winding. Since no breakage or tearing occurs at the time of processing, etc., various processing becomes possible, and the range of use is dramatically expanded.

  In the present invention, the polylactic acid-based film or sheet has a heating dimensional change rate within ± 3% in both the flow direction (MD direction) and the width direction (TD direction), preferably within ± 2%. Within ± 1%. When a polylactic acid film or sheet having such a heating dimensional change rate is used as a base material for a protective film, it will not melt or deform even under high temperature conditions exceeding, for example, 100 ° C., and heat resistance is required. It can be used even for various purposes.

In the present invention, the heating dimensional change rate is expressed by the following formula (1) when stored at 100 ° C. for 1 minute.
Heating dimensional change rate (%) = (L2−L1) / L1 × 100 (1)
(In the formula, L1 represents a marked line length before the test, and L2 represents a marked line length after the test).

  In the present invention, the polylactic acid film or sheet has a dimensional change rate of heating load within ± 3%, preferably within ± 2% in both the flow direction (MD direction) and the width direction (TD direction). Within ± 1%. When a polylactic acid film or sheet having such a heating load dimensional change rate is used as the base material of the protective film, it will not melt or deform even under high temperature conditions exceeding, for example, 100 ° C. Even necessary applications can be used sufficiently.

In the present invention, the heating load dimensional change rate is expressed by the following formula (2) when a load of 300 g per 1 mm ² is applied in the flow direction (MD direction) in an atmosphere of 100 ° C. and stored for 1 minute.
Heating load dimensional change rate (%) = (L4−L3) / L3 × 100 (2)
(In the formula, L3 represents the marked line length before the test, and L4 represents the marked line length after the test).

  In the present invention, a specific method for further improving the physical properties of the polylactic acid film or sheet includes, for example, a method of forming a film of a resin composition in which a modifier (E) is blended with polylactic acid (A). .

  Examples of the modifier (E) include (a) polyglycerin fatty acid ester or polyglycerin condensed hydroxy fatty acid ester, (b) a core-shell structure polymer having a graft layer outside the particulate rubber, and (c) soft fat. Group polyesters and the like can be mentioned. These can be used individually by 1 type or in combination of 2 or more types.

  In the present invention, the polylactic acid film or sheet comprises (a) a polyglycerol fatty acid ester and / or a polyglycerol condensed hydroxy fatty acid ester as a modifier (E) with respect to the polylactic acid (A). The weight ratio of A) to (a) polyglycerol fatty acid ester and / or polyglycerol condensed hydroxy fatty acid ester is 99: 1 to 80:20 (the former: the latter (total amount of (a))). Is preferable, and it is more preferable to contain so that it may become 95: 5-90: 10 (the former: the latter (total amount of (a))). Each of the polyglycerol fatty acid ester and the polyglycerol condensed hydroxy fatty acid ester can be used alone or in combination of two or more.

  (A) If the amount of the polyglycerin fatty acid ester and / or the polyglycerin condensed hydroxy fatty acid ester is too small, the effect of improving physical properties is not sufficient. On the other hand, if the amount of (a) polyglycerin fatty acid ester and / or polyglycerin condensed hydroxy fatty acid ester is too large, the crystallinity and crystallization rate tend to decrease, and (a) polyglycerin fatty acid ester and / or poly The glycerin condensed hydroxy fatty acid ester may bleed out. (A) When a polylactic acid-based film or sheet containing a polyglycerin fatty acid ester or a polyglycerin condensed hydroxy fatty acid ester in the above range is used as the base material of the protective film, the tear resistance is reduced without reducing the heat resistance. The effect that it can improve is produced.

  In the (a) polyglycerol fatty acid ester or polyglycerol condensed hydroxy fatty acid ester, the polyglycerol fatty acid ester is an ester obtained by reacting polyglycerol with a fatty acid. Examples of the polyglycerol that is a constituent component of the polyglycerol fatty acid ester include diglycerol, triglycerol, tetraglycerol, pentaglycerol, hexaglycerol, heptaglycerol, octaglycerol, nonaglycerol, decaglycerol, and dodecaglycerol. These are used individually by 1 type or in mixture of 2 or more types. The average degree of polymerization of polyglycerol is preferably 2 to 10.

  As the fatty acid which is the other component of the polyglycerol fatty acid ester, for example, a fatty acid having 12 or more carbon atoms is used. Specific examples of fatty acids include lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, eicosadienoic acid, arachidonic acid, behenic acid, erucic acid, ricinoleic acid, 12-hydroxystearic acid, hydrogenated Castor oil fatty acid and the like. These are used individually by 1 type or in mixture of 2 or more types.

  The polyglycerol condensed hydroxy fatty acid ester is an ester obtained by reacting polyglycerol and condensed hydroxy fatty acid. What was illustrated as a structural component of the said polyglycerol fatty acid ester as a polyglycerol which is a structural component of polyglycerol condensed hydroxy fatty acid ester is mentioned.

  The condensed hydroxy fatty acid which is the other component of the polyglycerol condensed hydroxy fatty acid ester is a condensate of hydroxy fatty acid. The hydroxy fatty acid may be any fatty acid having one or more hydroxyl groups in the molecule, and examples thereof include ricinoleic acid, 12-hydroxystearic acid, hydrogenated castor oil fatty acid, and the like. The condensation degree of the condensed hydroxy acid is, for example, 3 or more, preferably 3-8. The condensed hydroxy fatty acid is used alone or in combination of two or more.

  Commercially available products can be used as the polyglycerol fatty acid ester and the polyglycerol condensed hydroxy fatty acid ester. Examples of commercially available products of polyglycerin fatty acid esters include the tyrazole series such as trade names “Tirabazole VR-10” and “Tirabazole VR-2” manufactured by Taiyo Kagaku Co., Ltd.

  In the present invention, the polylactic acid-based film or sheet is obtained by adding, to the polylactic acid (A), a modifier (E) (b) a core-shell structure polymer having a graft layer outside the particulate rubber, It is preferable to contain the lactic acid (A) and (b) the core-shell structure polymer having a graft layer outside the particulate rubber so that the weight ratio is 99: 1 to 80:20 (the former: the latter), It is more preferable to contain so that it may become 97: 3-90: 10 (the former: the latter). (B) The core-shell structure polymer having a graft layer outside the particulate rubber can be used singly or in combination of two or more.

  (B) If the amount of the core-shell structure polymer having a graft layer outside the particulate rubber is too small, the effect of improving physical properties is not sufficient. On the other hand, if the amount of (b) the core-shell structure polymer having the graft layer on the outside of the particulate rubber is too large, the degree of crystallization and the crystallization speed are liable to decrease, and (b) the outside of the particulate rubber. In some cases, a core-shell structure polymer having a graft layer on the surface bleeds out. (B) When a polylactic acid film or sheet containing a core-shell structure polymer having a graft layer outside the particulate rubber in the above range is used as the base material of the protective film, without reducing the heat resistance, This produces the effect of improving tear resistance.

  In the core-shell structure polymer (b) having a graft layer outside the particulate rubber, examples of the particulate rubber constituting the core include acrylic rubber, butadiene rubber, and silicone / acrylic composite rubber. Can be mentioned. Examples of the polymer constituting the shell include styrene resins such as polystyrene and acrylic resins such as polymethyl methacrylate.

  The average particle diameter (aggregate of primary particles) of the core-shell structure polymer is, for example, 50 to 500 μm, preferably 100 to 250 μm. When this is blended with polylactic acid (A) and melt-kneaded, primary particles are dispersed. The average particle diameter of the primary particles is, for example, 0.1 to 0.6 μm.

  A commercial item can be used as said core-shell structure polymer. Examples of commercial products of the core-shell structure polymer include paraloid series (particularly, paraloid EXL series) such as trade name “Paraloid EXL2315” manufactured by Rohm and Haas Japan, and trade name “Metabrene” manufactured by Mitsubishi Rayon Co., Ltd. Metabrene S type such as “S-2001”, Metabrene W type such as “Metabrene W-450A”, Metabrene C type such as “Metabrene C-223A”, Metabrene E type such as “Metabrene E-901”, and the like.

  In the present invention, the polylactic acid film or sheet comprises (c) a soft aliphatic polyester as a modifier (E) and polylactic acid (A) and (c) soft fat with respect to the polylactic acid (A). It is preferable to contain it so that a weight ratio with a group polyester may be 95: 5-60: 40 (the former: latter), and it may contain so that it may become 90: 10-80: 20 (the former: latter). Further preferred. (C) A soft aliphatic polyester can be used individually by 1 type or in combination of 2 or more types.

  (C) If the amount of the soft aliphatic polyester is too small, the physical property modification effect is not sufficient. On the other hand, if the amount of (c) soft aliphatic polyester is too large, the degree of crystallization and the crystallization speed are likely to decrease, and (c) the soft aliphatic polyester may bleed out. (C) When a polylactic acid film or sheet containing a soft aliphatic polyester in the above range is used as the base material of the protective film, the effect of improving the tear resistance without lowering the heat resistance is produced. .

  (C) Soft aliphatic polyester includes aliphatic polyester and aliphatic-aromatic copolymer polyester. (C) The soft aliphatic polyester (aliphatic polyester, aliphatic-aromatic copolymer polyester) is a polyester obtained from a polyhydric alcohol such as a diol and a polycarboxylic acid such as a dicarboxylic acid, Examples include polyesters in which at least aliphatic diols are used and at least aliphatic dicarboxylic acids are used as dicarboxylic acids; polymers of aliphatic hydroxycarboxylic acids having 4 or more carbon atoms, and the like. Examples of the aliphatic diol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,2-butanediol, and 1,4-butane. Aliphatic diels having 2 to 12 carbon atoms such as diol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, cyclohexanediol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol ( And an alicyclic diol). Examples of the aliphatic dicarboxylic acid include succinic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid. Examples thereof include saturated aliphatic dicarboxylic acids having 2 to 12 carbon atoms (including alicyclic dicarboxylic acids) such as acids. In the polyester in which at least an aliphatic diol is used as the diol component and at least an aliphatic dicarboxylic acid is used as the dicarboxylic acid component, the ratio of the aliphatic diol to the entire diol component is, for example, 80% by weight or more, preferably 90%. % By weight or more, more preferably 95% by weight or more, and the remainder may be an aromatic diol or the like. In the polyester in which at least an aliphatic diol is used as the diol component and at least an aliphatic dicarboxylic acid is used as the dicarboxylic acid component, the proportion of the aliphatic dicarboxylic acid in the entire dicarboxylic acid component is, for example, 20% by weight. As mentioned above, Preferably it is 30 weight% or more, More preferably, it is 50 weight% or more, An aromatic dicarboxylic acid (for example, terephthalic acid etc.) etc. may be sufficient as the remainder. Examples of the aliphatic hydroxycarboxylic acids having 4 or more carbon atoms include hydroxycarboxylic acids having 4 to 12 carbon atoms such as hydroxybutyric acid, hydroxyvaleric acid, hydroxypentanoic acid, hydroxyhexanoic acid, hydroxydecanoic acid, and hydroxydodecanoic acid. Is mentioned. (C) The weight average molecular weight of the soft aliphatic polyester (aliphatic polyester, aliphatic-aromatic copolymer polyester) is, for example, 50,000 to 400,000, preferably 80,000 to 250,000.

  (C) Representative examples of soft aliphatic polyesters include polybutylene succinate, polybutylene succinate adipate, polyethylene succinate, polyethylene succinate adipate, polybutylene adipate terephthalate, polybutylene sebacate terephthalate, polyhydroxyl alkanoate Etc.

  (C) Commercially available products can be used as the soft aliphatic polyester. For example, as polybutylene succinate, trade name “GS Pla AZ91T” manufactured by Mitsubishi Chemical Corporation, as polybutylene succinate adipate, trade name “GS Pla AD92W” manufactured by Mitsubishi Chemical Corporation, as polybutylene adipate terephthalate, The product name “Eco-Flex” manufactured by BASF Japan may be mentioned.

  In this invention, the polylactic acid-type film or sheet | seat may contain various additives as needed in the range which does not impair the effect of this invention. Such additives include antioxidants, ultraviolet absorbers, plasticizers, stabilizers, mold release agents, antistatic agents, colorants (white pigments, etc.), anti-drip agents, flame retardants, hydrolysis inhibitors, A foaming agent, a filler, etc. are mentioned.

  In the present invention, since the polylactic acid film or sheet has a high degree of crystallization, it is excellent in solvent resistance. For example, the degree of swelling of the polylactic acid film or sheet is, for example, 2.5 or less, preferably 2.0 or less, with respect to any solvent of ethyl acetate and toluene. The degree of swelling was determined by immersing a film or sheet sample (50 mm × 50 mm × 0.05 mm thickness) in a solvent for 15 minutes, removing the solvent on the surface of the taken film or sheet sample with a waste cloth, and immersing the weight after immersion. Can be measured by dividing by previous weight.

  In the present invention, the polylactic acid film or sheet can maintain a high level of mechanical properties such as rigidity and elastic properties. For example, the initial elastic modulus of the polylactic acid film or sheet in the present invention is usually 1000 MPa or more, preferably 1500 MPa or more in the flow direction (MD direction). The upper limit of the initial elastic modulus is generally about 3500 MPa (for example, about 3000 MPa) in the flow direction (MD direction). The breaking strength of the polylactic acid film or sheet in the present invention is usually 30 MPa or more, preferably 35 MPa or more in the flow direction (MD direction). The upper limit of the breaking strength is generally about 150 MPa (for example, about 120 MPa).

  Furthermore, the elongation of the polylactic acid film or sheet in the present invention is usually 2.5% or more, preferably 3.5% or more in the flow direction (MD direction). The upper limit of elongation is generally about 15% (for example, about 12%) in the flow direction (MD direction). When (c) soft aliphatic polyester is used as the modifier (E), the elongation of the polylactic acid film or sheet is usually 5% or more, preferably 10 in the flow direction (MD direction). %, More preferably 20% or more, and the upper limit of elongation is generally 150%, preferably 120%, more preferably 100% in the flow direction (MD direction).

The initial elastic modulus, breaking strength, and elongation were measured using a tensile tester according to the plastic-tensile property test method of JIS K 7161.
Apparatus: Tensile tester (Autograph AG-20kNG, manufactured by Shimadzu Corporation)
Sample size: thickness 0.05 mm x width 10 mm x length 100 mm (note that the direction parallel to the length direction is the flow direction (MD) during film formation)
Measurement condition:
Distance between chucks: 50mm
Tensile speed: 300 mm / min

  In the present invention, the thickness of the polylactic acid film or sheet is not particularly limited, but is usually 10 to 500 μm, preferably 20 to 400 μm, more preferably 30 to 100 μm.

[Method for producing protective film]
The production method of the protective film in the present invention is as follows:
A method for producing a protective film, which is based on a polylactic acid film or sheet obtained by forming a resin composition containing polylactic acid (A) using a melt film formation method,
A melt film-forming step of melt-forming a resin composition;
After the melt film-forming step, the resin composition is cooled and solidified to obtain a film or sheet;
After the cooling and solidifying step, the film or sheet is heated, and has a crystallization promoting step for promoting crystallization of the film or sheet,
The resin temperature in the melt film formation step is within the range of the melting temperature (Tm) -15 ° C. to (Tm) + 15 ° C. in the temperature rising process of the resin composition,
In at least a part of the crystallization promoting step, crystallization of the film or sheet is promoted within a temperature range of crystallization temperature (Tc) + 10 ° C. to (Tc) + 50 ° C. in the temperature rising process of the resin composition. It is characterized by that.

  For example, a polylactic acid film or sheet is a polylactic acid film or sheet in which each component is uniformly dispersed by a continuous melt kneader such as a twin screw extruder, or a batch melt kneader such as a pressure kneader, a Banbury mixer, or a roll kneader. A lactic acid (A) -containing resin composition can be prepared, and this can be produced by forming a film and cooling and solidifying it by an extrusion method such as a T-die method or an inflation method, a calendar method, a polishing method, or the like. The melt film formation method is preferably a method in which a molten resin composition is formed into a desired thickness by passing through a gap between two metal rolls, and more preferably a calendar method. Polishing method, particularly preferably calendar method.

The resin temperature in the melt film forming step is within the range of the melting temperature (Tm) -15 ° C. to (Tm) + 15 ° C. in the temperature rising process of the resin composition. The melting temperature (Tm) of the resin composition is preferably in the range of −15 ° C. to (Tm) + 5 ° C., and the melting temperature (Tm) in the temperature rising process of the resin composition is in the range of −10 ° C. to (Tm). More preferably, the melting temperature (Tm) in the temperature rising process of the resin composition is in the range of −5 ° C. to (Tm).
In particular, when the resin composition does not contain the modifier (E), the melting temperature (Tm) -15 ° C. to (Tm) + 5 ° C. in the temperature rising process of the resin composition. It is preferable that it is within a range of the melting temperature (Tm) -10 ° C. to (Tm) in the temperature rising process of the resin composition.
In particular, when the resin composition further contains a modifier (E), the melting temperature (Tm) in the temperature rising process of the resin composition is in the range of −10 ° C. to (Tm) + 5 ° C. The melting temperature (Tm) in the process of raising the temperature of the resin composition is more preferably in the range of −5 ° C. to (Tm).
By setting to such a temperature range, there is an effect that orientation crystallization during film formation can be suppressed.

  In particular, from the viewpoint of always controlling to a predetermined temperature, it is desirable that the resin composition is brought into contact with a metal roll having a predetermined surface temperature in the melt film forming step. Accordingly, it is desirable that the polylactic acid (A) -containing resin composition be easily peelable from the metal roll also in this step. From this point of view, the addition of the above-mentioned acidic functional group-modified olefin polymer (B) is desirable. Is preferred.

Further, the method for producing a protective film according to the present invention includes a method of maintaining the resin composition within a certain temperature range after the melt film-forming step and before the cooling and solidifying step, whereby a residual stress of the resin composition is obtained. It is preferable to have a residual stress relaxation process that relaxes. The constant temperature (residual stress relaxation temperature) is not particularly limited, but is, for example, within a temperature range of (Tm) -70 ° C. to (Tm) -20 ° C., preferably (Tm) -60 ° C. to (Tm ) Within a temperature range of −20 ° C., more preferably within a temperature range of (Tm) −60 ° C. to (Tm) −23 ° C., and even more preferably (Tm) −50 ° C. to (Tm) −25 ° C. And is particularly preferably within the temperature range of (Tm) -50 ° C to (Tm) -30 ° C.
In particular, when the resin composition does not contain the modifier (E), the residual stress relaxation temperature is preferably within the temperature range of (Tm) -60 ° C to (Tm) -23 ° C. , (Tm) -50 ° C. to (Tm) -30 ° C. is more preferable.
In particular, when the resin composition further contains a modifier (E), the residual stress relaxation temperature is within the temperature range of (Tm) -60 ° C to (Tm) -20 ° C. Is more preferable, and is more preferably within a temperature range of (Tm) -60 ° C to (Tm) -23 ° C, and more preferably within a temperature range of (Tm) -50 ° C to (Tm) -25 ° C. , (Tm) -50 ° C to (Tm) -30 ° C is particularly preferable. There may be a difference in the preferable temperature range depending on the type of the modifier (E).
By setting to such a temperature range, the effect of relaxing the residual stress is further enhanced, and the risk of causing extreme heat shrinkage during use of the obtained film or sheet is further reduced, so that the obtained crystallized film or sheet is obtained. The shape can be maintained up to near the melting point of polylactic acid, and can be sufficiently used even in applications requiring heat resistance, which could not be used so far. In the residual stress relaxation step, a specific method for maintaining the resin composition at a constant temperature is not particularly limited, and examples thereof include a method of bringing a film sample into contact with a take-off roll maintained at a constant temperature.

  In at least a part of the crystallization promoting step, crystallization of the film or sheet is promoted within a temperature range of crystallization temperature (Tc) + 10 ° C. to (Tc) + 50 ° C. in the temperature rising process of the resin composition. However, it is preferable that crystallization is accelerated within the temperature range of the crystallization temperature (Tc) + 20 ° C. to (Tc) + 45 ° C. in the temperature rising process of the resin composition. It is more preferable that crystallization is accelerated within a temperature range of crystallization temperature (Tc) + 20 ° C. to (Tc) + 40 ° C. By setting to such a temperature range, the effect of promoting crystallization is further improved, and the production speed is further improved.

  In particular, from the viewpoint of always controlling to a predetermined temperature, it is desirable that the film or sheet is brought into contact with a metal roll having a predetermined surface temperature in the crystallization promoting step. Therefore, it is desirable that the film or sheet can be easily peeled off from the metal roll also in this step, and the addition of the above-mentioned acidic functional group-modified olefin polymer (B) is also preferable from this viewpoint.

  The time for the crystallization promoting step is preferably as long as possible, and ultimately depends on the degree of crystallization of the resin composition, so it cannot be specified unconditionally, but usually 10 to 120 seconds, preferably 20 to 90. Second, more preferably 30 to 60 seconds.

  In the crystallization promotion step, even if the crystallization temperature (Tc) in the temperature-decreasing process of the resin composition changes due to the addition of another crystal nucleating agent or the like, the measurement is performed in advance with a differential scanning calorimeter (DSC). By carrying out and grasping the maximum temperature of the exothermic peak accompanying the crystallization in the temperature lowering process, it is possible to always obtain the optimum temperature condition for the crystallization promoting step. At that time, the shape change of the film or sheet obtained by heating at the temperature hardly needs to be considered, but it is preferably a temperature at which the heat deformation rate of the obtained film or sheet is 40% or less. .

  A uniaxial or biaxial stretching process (preferably a biaxial stretching process) may be performed before and / or after the crystallization promoting step. In some cases, the crystallization can be further improved by performing the stretching treatment. The extending | stretching process temperature is 60-100 degreeC, for example.

  As a method for producing a polylactic acid film or sheet including the crystallization promoting step, a method of continuously performing from the melt film forming step to the cooling and solidifying step is preferable in terms of productivity because the processing time is shortened. Furthermore, it is more preferable to provide a crystallization step continuously after the cooling and solidification step (for example, passing a heating roll or the like). Examples of such a method include a method using a calendar film forming machine, a polishing film forming machine, and the like.

[Calendar film formation]
FIG. 1 shows a schematic diagram of an example of a calendar film forming machine used in such a manufacturing method. In the following, FIG. 1 will be described in detail.

  The resin composition in a molten state is rolled between four calender rolls of the first roll 1, the second roll 2, the third roll 3, and the fourth roll 4, and gradually thinned. It adjusts so that it may become desired thickness when passing between the roll 3 and the 4th roll 4. FIG. In the case of calendar film formation, the film formation of the resin composition in the first roll 1 to the fourth roll 4 corresponds to the “melt film formation process”. The take-off roll 5 indicates a roll group in which the melt-formed resin composition 8 first comes into contact. The take-off roll 5 is composed of one or two or more (three in FIG. 1) roll groups. 4 plays a role of peeling the molten resin composition 8. Thus, when the take-off roll 5 is composed of a plurality of rolls and the temperature of each roll can be adjusted, the temperature of each roll is preferably the same, but if within the desired temperature range, May be different.

  The take-off roll 5 plays a role of relaxing the residual stress by bringing the film sample into contact with the take-off roll (residual stress relaxation step). In this case, the surface temperature of the take-off rolls (three in FIG. 1) is made substantially the same, and the temperature is often the stress relaxation temperature (° C.), but the three take-off roll temperatures are different from each other. It may be. In this case, it is preferable that these take-off roll temperatures are all within the above-described temperature range.

  The two cooling rolls 6 and 7 serve to cool and solidify the resin composition 8 by allowing the resin composition 8 to pass between them, and to mold the surface into a desired shape (cooling). Solidification step). Therefore, one roll (for example, the cooling roll 6) is usually a metal roll, and the roll surface is designed to bring out the surface shape of the resin composition 8, and the other roll (for example, the cooling roll 7). ) Rubber rolls are used. In addition, the arrow in a figure shows the rotation direction of a roll. 9 is a bank (resin pool).

  Thereafter, although not shown in FIG. 1, the cooled and solidified film is heated with a heating roll controlled at an arbitrary temperature to promote crystallization (crystallization promoting step).

[Polishing film formation]
FIG. 2 shows a schematic diagram of an example of a polishing film forming machine used in such a manufacturing method. In the following, FIG. 2 will be described in detail.

  An extruder tip 10 of an extruder (not shown) is disposed between the heated second roll 2 and third roll 3, and the second roll 3 and third roll 3 are set at a preset extrusion speed. In the meantime, the molten resin composition 8 is continuously extruded. The extruded resin composition 8 is rolled and thinned between the second roll 2 and the third roll 3, and finally has a desired thickness when it passes between the third roll 3 and the fourth roll 4. It is adjusted to become. In the case of polishing film formation, film formation of the resin composition 8 on the second roll 4 to the fourth roll 4 corresponds to a “melt film formation process”. Thereafter, it passes through one or more (three in FIG. 2) take-off rolls 5 (residual stress relaxation step), and finally passes through cooling rolls (cooling rolls 6 and 7 in FIG. 2) (cooling solidification). Step), a solidified film or sheet is produced.

  Thereafter, although not shown in FIG. 2, the cooled and solidified film is heated with a heating roll controlled to an arbitrary temperature to promote crystallization (crystallization promoting step).

  In the present invention, the surface of the base material is subjected to a conventional surface treatment, for example, chromic acid treatment, ozone exposure, flame exposure, high-voltage impact exposure, ionizing radiation, in order to enhance the adhesion to the adjacent layer as necessary. An oxidation treatment or the like by a chemical or physical method such as treatment may be performed.

[Removable adhesive layer]
The protective film of the present invention has a removable pressure-sensitive adhesive layer on at least one surface of the substrate.

  The pressure-sensitive adhesive constituting the removable pressure-sensitive adhesive layer is not particularly limited. For example, a rubber-based pressure-sensitive adhesive, an acrylic pressure-sensitive adhesive, a vinyl alkyl ether-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, a polyester-based pressure-sensitive adhesive, and a polyamide-based pressure-sensitive adhesive layer. Known adhesives such as pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, styrene-diene block copolymer-based pressure-sensitive adhesives, and adhesives with improved creep characteristics in which a hot-melt resin having a melting point of about 200 ° C. or less is blended with these pressure-sensitive adhesives An agent can be used 1 type or in combination of 2 or more types. As long as it has removability, the pressure-sensitive adhesive may be any known removable pressure-sensitive adhesive such as a solvent type, an emulsion type, or a hot melt type.

  In general, as the removable pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive having a base polymer of natural rubber or various synthetic rubbers; one or more of (meth) acrylic acid alkyl esters are used as monomer components. An acrylic pressure-sensitive adhesive having an acrylic polymer (homopolymer or copolymer) as a base polymer is used. In the present invention, an acrylic adhesive having an acrylic polymer as a base polymer is particularly preferably used.

Examples of the (meth) acrylic acid alkyl ester used as the monomer component of the acrylic polymer include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and (meth) acrylic. Isopropyl acid, butyl (meth) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, ( Heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isodecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, Pentamethyl (meth) acrylate, hexadecyl (meth) acrylate, Meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl and the like (meth) (meth) acrylic acid C _1-20 alkyl esters such as eicosyl acrylate.

  The acrylic polymer is a unit corresponding to another monomer component copolymerizable with the (meth) acrylic acid alkyl ester, if necessary, for the purpose of modifying cohesive strength, heat resistance, crosslinkability and the like. May be included. Examples of such a monomer component include an aliphatic cyclic skeleton such as cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cyclohexylmethyl (meth) acrylate, and bornyl (meth) acrylate (meta ) Acrylic acid ester; (meth) acrylic acid ester having an aromatic carbon ring such as phenyl (meth) acrylate and benzyl (meth) acrylate; acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, Carboxylic group-containing monomers such as maleic acid, fumaric acid and crotonic acid; Acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, (meth) Acrylic acid hydroxybuty , Hydroxyl group-containing monomers such as hydroxyhexyl (meth) acrylate, hydroxyoctyl (meth) acrylate, hydroxydecyl (meth) acrylate, hydroxylauryl (meth) acrylate, (4-hydroxymethylcyclohexyl) methyl methacrylate; Contains sulfonic acid groups such as sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, (meth) acryloyloxynaphthalene sulfonic acid Monomer; (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methylolpropane (meth) a (N-substituted) amide-containing monomers such as rilamide; (meth) acrylic such as aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, and t-butylaminoethyl (meth) acrylate Acid aminoalkyl monomers; (meth) acrylic acid alkoxyalkyl monomers such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate; N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N- Maleimide monomers such as phenylmaleimide; N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-laurylitaconimide Itaconimide monomers such as conimide; succinimide monomers such as N- (meth) acryloyloxymethylenesuccinimide, N- (meth) acryloyl-6-oxyhexamethylenesuccinimide, N- (meth) acryloyl-8-oxyoctamethylenesuccinimide; Vinyl acetate, vinyl propionate, N-vinyl pyrrolidone, methyl vinyl pyrrolidone, vinyl pyridine, vinyl piperidone, vinyl pyrimidine, vinyl piperazine, vinyl pyrazine, vinyl pyrrole, vinyl imidazole, vinyl oxazole, vinyl morpholine, N-vinyl carboxylic acid amides, Vinyl monomers such as styrene, α-methylstyrene, N-vinylcaprolactam; cyano group-containing monomers such as acrylonitrile and methacrylonitrile Epoxy group-containing acrylic monomers such as glycidyl (meth) acrylate; polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, methoxyethylene glycol (meth) acrylate, methoxypolypropylene glycol (meth) acrylate, etc. Glycol-based acrylic ester monomers; N- (meth) acryloylmorpholine, tetrahydrofurfuryl (meth) acrylate, fluorine (meth) acrylate, silicone (meth) acrylate and other heterocyclic rings, halogen atoms, silicon atoms, etc. Monomers: hexanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl Recall di (meth) acrylate, pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, epoxy acrylate, polyester acrylate, urethane acrylate, etc. Polyfunctional monomers; Olefin monomers such as isoprene, butadiene, and isobutylene; Vinyl ether monomers such as vinyl ether. These monomer components can be used alone or in combination of two or more.

  The acrylic polymer can be produced by a known radical polymerization method such as solution polymerization, bulk polymerization, and emulsion polymerization. The acrylic polymer may be any of a random copolymer, a block copolymer, a graft polymer, and the like. In polymerization, a commonly used polymerization initiator or chain transfer agent can be used.

  The weight average molecular weight of the base polymer constituting the pressure-sensitive adhesive is, for example, 10,000 to 5,000,000, preferably 20,000 to 1,000,000. If the weight average molecular weight of the base polymer is too low, the adherence to the adherend is excellent, but contamination such as adhesive residue tends to occur on the adherend after re-peeling. On the other hand, when the weight average molecular weight of the base polymer is too high, contamination due to adhesive residue or the like on the adherend after re-peeling is reduced, but the followability to the adherend tends to be lowered.

  For adhesives, in addition to the base polymer, if necessary, crosslinking agents (epoxy crosslinking agents, isocyanate crosslinking agents, melamine crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, metal chelate compounds, etc.), crosslinking Accelerator (crosslinking catalyst), tackifier (for example, rosin derivative resin, polyterpene resin, petroleum resin, oil-soluble phenol resin, etc.), thickener, plasticizer, filler, foaming agent, anti-aging agent, antioxidant And an appropriate additive such as an ultraviolet absorber, an antistatic agent, a surfactant, a leveling agent, a colorant, a flame retardant, and a silane coupling agent. In particular, it is preferable to add a crosslinking agent in order to impart removability to the pressure-sensitive adhesive.

  The removable pressure-sensitive adhesive layer can be formed by a known or conventional method. For example, a method of applying the pressure-sensitive adhesive composition onto a base material (if an intermediate layer is present on the base material, the intermediate layer), a method of applying the pressure-sensitive adhesive composition onto an appropriate separator to form a pressure-sensitive adhesive layer Thereafter, a method of transferring (transferring) the pressure-sensitive adhesive layer onto a base material (in the case where an intermediate layer is present on the base material, the intermediate layer) may be mentioned. The coating can be performed by a coater, an extruder, a printing machine or the like generally used for forming the pressure-sensitive adhesive layer.

  The thickness of the releasable pressure-sensitive adhesive layer can be appropriately selected depending on the application and the like, and is, for example, about 1 to 100 μm, preferably about 1 to 50 μm.

  The adhesive strength at 25 ° C. of the releasable pressure-sensitive adhesive layer (180 ° peel peeling, polyethylene terephthalate film, tensile speed 300 mm / min) may be in a range where re-peeling is possible, for example, less than 3 N / 20 mm. . The lower limit is, for example, about 0.01 N / 20 mm.

  The protective film of the present invention may have another layer (intermediate layer) between the substrate and the releasable pressure-sensitive adhesive layer as necessary. Moreover, a separator for protecting the removable pressure-sensitive adhesive layer may be provided on the removable pressure-sensitive adhesive layer until the protective film is used.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. The present invention is not limited by these. In addition, evaluation in an Example etc. was performed as follows.

  The materials used in the examples are shown below.

<Polylactic acid (A)>
A1: Trade name “Terramac TP-4000” (manufactured by Unitika)
<Acid functional group-modified olefin polymer (B)>
B1: Maleic anhydride group-containing modified polypropylene (weight average molecular weight 32000, acid value 52 mgKOH / g,
(Product name “Yumex 1010”, manufactured by Sanyo Chemical Industries)
<Fluoropolymer (C)>
C1: Acrylic-modified polytetrafluoroethylene (trade name “Metabrene A-3000”, manufactured by Mitsubishi Rayon Co., Ltd.)
<Crystal Accelerator (D)>
D1: zinc phenylphosphonate (trade name “Eco Promote”, manufactured by Nissan Chemical Industries, Ltd.)
<Modifier (E)>
E (a): polyglycerol fatty acid ester (number average molecular weight Mn1300,
Product name “Tirabazole VR-17” (manufactured by Taiyo Kagaku)
E (b): Core-shell structure polymer (acrylic rubber / polymethyl methacrylate-styrene core-shell structure polymer,
Product name “Paraloid EXL2315” manufactured by Dow Chemical Co.)
E (c): Soft aliphatic polyester (polybutylene adipate terephthalate,
(Product name "Eco-Flex", manufactured by BASF Japan)

(Examples 1-7)
A resin composition was prepared at the blending ratio shown in Table 1 below, melted and kneaded with a Banbury mixer, and then a calender film was formed with a reverse L-shaped four-calendar so as to have a thickness of 50 μm (melting). Film forming step). Next, as shown in FIG. 1, immediately after the melt film formation step, three rolls (take-off rolls) that can be heated to an arbitrary temperature are arranged so that the melt-formed resin composition can pass alternately up and down. Then, the resin composition was solidified by passing through a cooling roll to produce a film. Thereafter, as shown in Table 1 below, the cooled and solidified film was heated with a heating roll controlled to an arbitrary temperature to promote crystallization (crystallization promoting step).

  The temperature of the resin composition in the melt film formation step (“resin temperature in the melt film formation step”) was the surface temperature of the roll corresponding to the fourth roll 4 in FIG. Regarding the temperature of the resin composition in the crystallization promotion step (“crystallization promotion temperature”), the surface temperature of the heating roll was set as the crystallization promotion temperature. The film forming speed was 5 m / min.

(Comparative Examples 1-9)
A resin composition was prepared at a blending ratio shown in Table 2 below, and a calendar film was formed under the film forming conditions shown in Table 2 except that the crystallization promotion step was not performed.

  The physical properties of the substrate were measured as follows.

<Melting temperature (° C)>
The temperature at the top of the endothermic peak that accompanies the melting in the re-heating process of the resin composition after film formation, measured by DSC (differential scanning thermal analyzer), is the melting temperature (Tm; also referred to as crystal melting peak temperature). It was.

<Crystallization temperature (℃)>
The temperature at the peak top of the exothermic peak accompanying the crystallization in the temperature rising process from room temperature of the resin composition after film formation, measured by DSC, is the crystallization temperature (Tc; crystallization temperature at temperature rising, crystallization). Also called peak temperature).

<Resin temperature (° C) in melt film formation process>
As described above, the surface temperature of the fourth roll was measured in both the example and the comparative example, and was defined as “resin temperature in the melt film formation process” (resin temperature in the melt film formation process).

<Residual stress relaxation temperature (℃)>
In this embodiment, the residual stress was relaxed by bringing the film sample into contact with a take-off roll. At that time, the surface temperature (take-off roll temperature) of the three take-off rolls in FIG. 1 was made substantially the same, and the temperature was taken as the stress relaxation temperature (° C.). Further, the three take-off roll temperatures may be different from each other as long as they are within the temperature range.

<Acceleration temperature for crystallization (℃)>
In this embodiment, the deposited film was heated with a heating roll controlled to an arbitrary temperature to promote crystallization. This heating roll temperature was defined as the crystallization acceleration temperature.

<Film formation results>
(1) Plate out to roll: Evaluate the surface of the roll by visual inspection, and determine that there is no contamination on the surface of the roll as "O" (None) and that the surface of the roll is dirty as "X" (Yes). did.
(2) Peelability: Evaluated by the peelability of the melt-formed resin composition from the fourth roll 4 in FIG. 1, “○” (good) indicates that the take-off roll 5 can be taken off, and the take-off roll 5 The state where it was not possible to pick up was determined as “x” (defective).
(3) Film surface state: The obtained film surface is visually observed, and the film surface is smooth and smooth, “◯” (good), bank mark (unevenness due to uneven flow of resin) and shark skin The state with a pinhole was determined as “x” (defective).

<Tear strength (N / mm)>
JIS K7128-3 Plastics-Test method for tear strength of films and sheets-Part 3: Measured according to the right angle tear method. The measurement apparatus and measurement conditions used are as follows.
Apparatus: Tensile tester (Autograph AG-20kNG, manufactured by Shimadzu Corporation)
Sample size: Specimen shape based on JIS standard
Condition: Tensile speed 200mm / min
In addition, the sample used for evaluation was cut out so that the tearing direction was the flow direction (hereinafter referred to as MD direction) during film formation.
Tear strength calculation method: Calculated using the following equation (3).
T = (F / d) (3)
T: Tear strength (N / mm)
F: Maximum tensile load (N)
d: Test piece thickness (mm)

<Amount of crystallization after film formation ΔHc ′ (J / g)>
After measuring by DSC, the heat quantity ΔHc (J / g) of the exothermic peak accompanying crystallization in the temperature rising process of the film sample after film formation, and then heating to 200 ° C. and cooling to 0 ° C. Again, from the amount of heat ΔHm (J / g) associated with melting when the temperature is raised, the amount of crystallization after film formation (melting endotherm of the crystallization part during film formation) using the following equation (5): ΔHc ′ was calculated.
ΔHc ′ = ΔHm−ΔHc (5)

The DSC used in the measurement of the crystallization temperature, the melting temperature, the relative crystallization rate, and the crystallization heat amount ΔHc ′ after film formation is as follows.
Device: DSC6220 manufactured by SII Nano Technology
The measurement conditions are as follows.
Measurement temperature range: 20 ° C. → 200 ° C. → 0 ° C. → 200 ° C. (In other words, following the measurement in the temperature increasing process from 20 ° C. to 200 ° C., the measurement in the temperature decreasing process from 200 ° C. to 0 ° C. is performed. Finally, we measured in the process of re-heating from 0 ° C to 200 ° C)
Temperature increase / decrease rate: 2 ° C / min
Measurement atmosphere: under nitrogen atmosphere (200 ml / min)
In addition, since there was no exothermic peak accompanying crystallization in the reheating process, it was determined that the crystallizable region crystallized 100% at a temperature decreasing rate of 2 ° C./min. The validity of the calculation formula was confirmed.

<Heating dimensional change rate>
The film was cut out 100 mm × 100 mm, 50 mm marked lines were written in each of the flow direction (hereinafter referred to as MD direction) and the width direction (hereinafter referred to as TD direction) during film formation, and the film was heated to 120 ° C. The dimensional change after taking out for 1 minute and taking out was confirmed.
Heating dimensional change rate calculation method: The marked line length L1 before the test and the marked line length L2 after the test were measured and calculated using the following formula (1).
Heating dimensional change rate (%) = (L2−L1) / L1 × 100 (1)
(Pass / fail judgment) Each of the MD direction and the TD direction is acceptable within ± 3%.

<Heat load dimensional change rate>
Cut out the film to 100 mm (MD direction) × 20 mm (TD direction), write a 50 mm rating line in the MD direction, apply a load of 300 g per mm ^{2 in} the MD direction, and put it in an oven heated to 100 ° C. for 1 minute, The dimensional change of MD after taking out was confirmed.
Calculation method of heating load dimensional change rate: The evaluation line length L3 before the test and the evaluation line length L4 after the test were measured and calculated using the following formula (2).
Heating dimensional change rate (%) = (L4−L3) / L3 × 100 (2)
(Pass / fail judgment) Acceptance is within ± 3%.
In addition, this evaluation is a substitute evaluation in consideration of the drying process at the time of actual pressure-sensitive adhesive coating, and it is assumed that a certain amount of tension is applied to the film and wound into a roll.

  The evaluation results of Examples 1 to 7 and Comparative Examples 1 to 9 are shown in Tables 1 and 2 below. First, in Example 1 and Comparative Examples 1 to 3 to which no modifier was added, Example 1 was shown to be excellent in tear resistance and heat resistance. On the other hand, Comparative Example 1 having no crystallization step has good tear resistance, but cannot withstand deformation under heating load because the amount of crystallization heat is small. In Comparative Example 2, the heat resistance is good because it is crystallized during film formation, but the tear resistance is poor. Further, in Comparative Example 3, since the take-off roll temperature is low, the residual stress is not relaxed, and both the tear resistance and the heat resistance are poor.

  In Examples 2 to 3 and Comparative Examples 4 to 5 in which E (a) was added as a modifier, Examples 2 to 3 were shown to have excellent tear resistance and heat resistance. Furthermore, the tear strength is higher than that of Example 1 to which no modifier is added, and the effect of blending the modifier is observed. On the other hand, Comparative Example 4 having no crystallization process has good tear resistance, but cannot withstand deformation under heating load because the amount of crystallization heat is small. In Comparative Example 3, the heat resistance is good because it is crystallized during film formation, but the tear resistance is poor.

  In Examples 4 to 5 and Comparative Examples 6 to 7 to which E (b) was added as a modifier, Examples 4 to 5 were shown to have excellent tear resistance and heat resistance. Furthermore, the tear strength is higher than that of Example 1 to which no modifier is added, and the effect of blending the modifier is observed. On the other hand, Comparative Example 6 having no crystallization step has good tear resistance, but cannot withstand deformation under heating load because the amount of crystallization heat is small. Further, Comparative Example 5 has good heat resistance because it is crystallized during film formation, but has poor tear resistance.

  In Examples 6 to 7 and Comparative Examples 8 to 9 to which E (c) was added as a modifier, Examples 6 to 7 were shown to have excellent tear resistance and heat resistance. Furthermore, the tear strength is higher than that of Example 1 to which no modifier is added, and the effect of blending the modifier is observed. On the other hand, Comparative Example 8 having no crystallization process has good tear resistance, but cannot withstand deformation under heating load because the amount of crystallization heat is small. Further, Comparative Example 7 has good heat resistance because it is crystallized during film formation, but has poor tear resistance.

DESCRIPTION OF SYMBOLS 1 1st roll 2 2nd roll 3 3rd roll 4 4th roll 5 Take off roll 6 Cooling roll 7 Cooling roll 8 Resin composition 9 Bank (resin pool)
10 Extruder tip

Claims (22)

A protective film having a releasable pressure-sensitive adhesive layer on at least one surface of a substrate,
The substrate is
Containing polylactic acid (A),
The tear strength (JIS K7128-3 Plastics-Test method for tear strength of films and sheets-Part 3: Conforms to the right-angled tear method) is at least 100 N / mm when tearing in the flow direction (MD direction) ,
The following formula (1) when stored for 1 minute in an atmosphere of 100 ° C.
Heating dimensional change rate (%) = (L2−L1) / L1 × 100 (1)
(In the formula, L1 indicates the length of the marked line before the test, L2 indicates the length of the marked line after the test), and the heating dimensional change rate is ± in both the flow direction (MD direction) and the width direction (TD direction). The following formula (2) when the load is 300 g per 1 mm ² in the flow direction (MD direction) and stored for 1 minute in an atmosphere of 3% or less and 100 ° C.
Heating load dimensional change rate (%) = (L4−L3) / L3 × 100 (2)
(Wherein L3 is the length of the marked line before the test and L4 is the length of the marked line after the test), the dimensional change rate of the heating load is within ± 3% in the flow direction (MD direction).
A protective film comprising a polylactic acid film or sheet.   The protective film according to claim 1, wherein the polylactic acid film or sheet constituting the substrate further contains a modifier (E).   The polylactic acid-based film or sheet constituting the substrate has (a) a polyglycerin fatty acid ester and / or a polyglycerin condensed hydroxy fatty acid ester as the modifier (E) with respect to the polylactic acid (A). The weight ratio of polylactic acid (A) to (a) polyglycerol fatty acid ester and / or polyglycerol condensed hydroxy fatty acid ester is 99: 1 to 80:20 (the former: the latter (total amount of (a))). The protective film according to claim 2, which is contained.   A core-shell structure polymer in which the polylactic acid film or sheet constituting the substrate has a graft layer on the outside of the particulate rubber as the modifier (E) with respect to the polylactic acid (A) In such a manner that the weight ratio of polylactic acid (A) to (b) core-shell structure polymer having a graft layer outside the particulate rubber is 99: 1 to 80:20 (the former: the latter). The protective film according to claim 2 or 3.   The polylactic acid film or sheet constituting the substrate is composed of (c) a soft aliphatic polyester as the modifier (E), polylactic acid (A) and (c). The protective film according to any one of claims 2 to 4, wherein the protective film is contained so that a weight ratio to the soft aliphatic polyester is 95: 5 to 60:40 (the former: the latter).   The polylactic acid-based film or sheet constituting the substrate further comprises polylactic acid (A) (provided that the modifying agent (E) contains polylactic acid (A) and the modifying agent (E)). The composition comprises 0.1 to 10 parts by weight of an acidic functional group-modified olefin polymer (B) having an acid value of 10 to 70 mgKOH / g and a weight average molecular weight of 10,000 to 80,000 per 100 parts by weight. The protective film of any one of -5.   The protective film according to claim 6, wherein the acidic functional group of the acidic functional group-modified olefin polymer (B) is an acid anhydride group.   The polylactic acid-based film or sheet constituting the substrate further comprises polylactic acid (A) (provided that the modifying agent (E) contains polylactic acid (A) and the modifying agent (E)). The protective film according to any one of claims 1 to 7, comprising 0.5 to 15 parts by weight of the fluoropolymer (C) with respect to 100 parts by weight of the composition).   The protective film according to claim 8, wherein the fluorine-based polymer (C) is a tetrafluoroethylene-based polymer.   The polylactic acid-based film or sheet constituting the substrate further comprises polylactic acid (A) (provided that the modifying agent (E) contains polylactic acid (A) and the modifying agent (E)). The protective film according to any one of claims 1 to 9, comprising 0.1 to 15 parts by weight of a crystallization accelerator (D) with respect to 100 parts by weight of the composition). A method for producing a protective film, which is based on a polylactic acid film or sheet obtained by forming a resin composition containing polylactic acid (A) using a melt film formation method,
A melt film-forming step of melt-forming a resin composition;
After the melt film-forming step, the resin composition is cooled and solidified to obtain a film or sheet;
After the cooling and solidifying step, the film or sheet is heated, and has a crystallization promoting step for promoting crystallization of the film or sheet,
The resin temperature in the melt film formation step is within the range of the melting temperature (Tm) -15 ° C. to (Tm) + 15 ° C. in the temperature rising process of the resin composition,
In at least a part of the crystallization promoting step, crystallization of the film or sheet is promoted within a temperature range of crystallization temperature (Tc) + 10 ° C. to (Tc) + 50 ° C. in the temperature rising process of the resin composition. The manufacturing method of the protective film characterized by the above-mentioned. A residual stress relaxation step after the melt film formation step and before the cooling and solidification step;
  The method for producing a protective film according to claim 11, wherein in the residual stress relaxation step, the resin composition is maintained in a temperature range of (Tm) -70 ° C to (Tm) -20 ° C. The method for producing a protective film according to claim 11 or 12, wherein the resin composition further contains a modifier (E). The resin composition comprises (a) a polyglycerol fatty acid ester and / or a polyglycerol condensed hydroxy fatty acid ester as the modifier (E) with respect to the polylactic acid (A). 14) The polyglycerin fatty acid ester and / or the polyglycerin condensed hydroxy fatty acid ester is contained so that the weight ratio is 99: 1 to 80:20 (the former: the latter (total amount of (a))). Manufacturing method of the protective film. When the resin composition is a polylactic acid (A), the modifying agent (E) is (b) a core-shell structure polymer having a graft layer outside the particulate rubber, and the polylactic acid (A). (B) It contains so that the weight ratio with the core-shell structure polymer which has a graft layer on the exterior of particulate rubber may become 99: 1-80: 20 (the former: the latter). A method for producing a protective film. The resin composition comprises (c) a soft aliphatic polyester as the modifier (E) with respect to the polylactic acid (A), and a polylactic acid (A) and (c) a soft aliphatic polyester. The manufacturing method of the protective film of any one of Claims 13-15 contained so that a weight ratio may be 95: 5-60: 40 (the former: the latter). The resin composition is further added to 100 parts by weight of polylactic acid (A) (provided that the modifier (E) contains a polylactic acid (A) and a modifier (E)). In any one of Claims 11-16 containing 0.1-10 weight part of acidic functional group modification | denaturation olefin polymers (B) whose acid value is 10-70 mgKOH / g and whose weight average molecular weight is 10000-80000. The manufacturing method of the protective film of description. The method for producing a protective film according to claim 19, wherein the acidic functional group of the acidic functional group-modified olefin polymer (B) is an acid anhydride group. The resin composition is further added to 100 parts by weight of polylactic acid (A) (provided that the modifier (E) contains a polylactic acid (A) and a modifier (E)). The manufacturing method of the protective film of any one of Claims 11-18 containing 0.5-15 weight part of fluorine-type polymers (C). The method for producing a protective film according to claim 19, wherein the fluoropolymer (C) is a tetrafluoroethylene polymer. The resin composition is further added to 100 parts by weight of polylactic acid (A) (provided that the modifier (E) contains a polylactic acid (A) and a modifier (E)). The manufacturing method of the protective film of any one of Claims 11-20 containing 0.1-15 weight part of crystallization promoters (D). The method for producing a protective film according to any one of claims 11 to 21, wherein the melt film formation method is a calendar method.

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