JPWO2009063694A1 - Method for producing cellulose ester film and cellulose ester film - Google Patents

Abstract

An object of the present invention is to provide a method for producing a cellulose ester film with high foreign matter failure and high production efficiency, and has been achieved by the following. In a method for producing a cellulose ester film in which at least a cellulose ester, an ultraviolet absorber and a plasticizer are mixed and melted, extruded from a die, and cast on a cooling roll, a means for supplying heated gas to a die discharge port, A method for producing a cellulose ester film, comprising: means for exhausting, means for cooling the exhausted gas and separating a compound contained in the exhausted gas from the gas, and means for recovering the separated compound .

Description

  The present invention relates to a method for producing a cellulose ester film useful as an optical film for liquid crystal display devices and the like, and a cellulose ester film.

  As a method for producing a cellulose ester film useful as an optical film, a melt casting method in which cellulose ester is heated and melted and extruded from a die onto a cooling roll is known.

  The melt casting method originally requires a large amount of plasticizer because the melt viscosity of cellulose ester is high, and is still forced to be heated at a high temperature. The ultraviolet absorber usually added to the plasticizer and the cellulose film by high-temperature heating volatilizes in the heating process and is likely to be deposited near the manufacturing apparatus, particularly the die lip, to cause process contamination. Contamination in the vicinity of the lip further leads to foreign matter failure of the film, which has been a major obstacle to increasing production efficiency.

  Patent Document 1 describes that a low molecular component that volatilizes from a molten resin discharged from a die is sucked and removed.

However, this method alone does not solve the problem of immediately clogging the piping that is the passage of the sucked gas because of the large amount of the volatilized plasticizer, and the production efficiency has not been improved. In addition, since the amount of the recovered compound becomes enormous, it is necessary to provide a treatment method separately.
JP 2006-335050 A

  An object of this invention is to provide the manufacturing method of a cellulose-ester film with few foreign material failures and high production efficiency.

  It is another object of the present invention to provide a technique for reusing a huge amount of collected material obtained by the manufacturing method.

  The object of the present invention has been achieved by the following means.

  1. In a method for producing a cellulose ester film in which at least a cellulose ester, an ultraviolet absorber and a plasticizer are mixed and melted, extruded from a die, and cast on a cooling roll, a means for supplying heated gas to a die discharge port, A method for producing a cellulose ester film, comprising: means for exhausting, means for cooling the exhausted gas and separating a compound contained in the exhausted gas from the gas, and means for recovering the separated compound .

  2. The method for producing a cellulose ester film according to the above 1, wherein the means for cooling the exhausted gas and separating the compound contained in the exhausted gas from the gas is a rotating drum.

  3. 3. The method for producing a cellulose ester film according to 1 or 2, wherein the means for recovering the separated compound is a blade adjacent to the rotating drum.

  4). A cellulose ester film comprising at least a cellulose ester, an ultraviolet absorber and a plasticizer, wherein the cellulose ester film contains the recovered compound described in any one of 1 to 3 above.

  According to the present invention, it is possible to provide a method for producing a cellulose ester film with high foreign matter failure and high production efficiency. Moreover, it became possible to provide the cellulose-ester film by which the bleed-out was improved using the collection | recovery obtained by the manufacturing method.

Schematic showing around the die of the manufacturing apparatus of the present invention Schematic showing the entire cellulose ester film production apparatus of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mixed melt 2 Die 3 Heated gas 4-1 Gas containing volatile substance 4-2 Gas from which volatile substance was removed 5 Rotating drum 6 Blade 7 Collected material 8 Heater for gas heating 9 Heat exchanger 101 Extruder 102 Filter 103 Static mixer 104 Die (including thickness adjusting means)
DESCRIPTION OF SYMBOLS 105 Touch roll 106 1st cooling roll 107 2nd cooling roll 108 Peeling roll 109 Dancer roll 110 Stretcher 111 Slitter 112 Thickness measuring means 113 Embossing ring and back roll 114 Winding machine 115 Film wound up

<Cellulose ester film>
The cellulose ester film of the present invention comprises at least a cellulose ester, an ultraviolet absorber and a plasticizer.

<Cellulose ester>
The cellulose ester of the present invention is not particularly limited, but is a carboxylic acid ester having about 2 to 22 carbon atoms as a cellulose ester capable of melt casting film formation, and may be an aromatic carboxylic acid ester, particularly having a carbon number. A lower fatty acid ester of 6 or less is preferable.

  The acyl group bonded to the hydroxyl group may be linear or branched or may form a ring. Furthermore, another substituent may be substituted. When the degree of substitution is the same, birefringence decreases when the number of carbon atoms is large, and therefore, the number of carbon atoms is preferably selected from acyl groups having 2 to 6 carbon atoms. The cellulose ester preferably has 2 to 4 carbon atoms, more preferably 2 to 3 carbon atoms.

  Specifically, the cellulose ester includes cellulose acetate propionate, cellulose acetate butyrate, or a mixed fatty acid ester of cellulose to which a propionate group or a butyrate group is bonded in addition to an acetyl group such as cellulose acetate propionate butyrate. Can be used.

  The butyryl group forming butyrate may be linear or branched. As the cellulose ester preferably used in the present invention, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, and cellulose acetate phthalate are particularly preferably used.

  Preferred cellulose esters other than cellulose acetate phthalate for the present invention preferably satisfy the following formulas (1) and (2).

Formula (1) 2.0 <= X + Y <= 3.0
Formula (2) 0 ≦ Y ≦ 1.5
In the formula, X is the degree of substitution of the acetyl group, and Y is the degree of substitution of the propionyl group or butyryl group, or a mixture thereof.

  Further, in order to obtain optical characteristics that meet the purpose, resins having different degrees of substitution may be mixed and used. The mixing ratio is preferably 10:90 to 90:10 (mass ratio).

  Of these, cellulose acetate propionate is particularly preferably used. In cellulose acetate propionate, 1.0 ≦ X ≦ 2.5, preferably 0.1 ≦ Y ≦ 1.5, and 2.0 ≦ X + Y ≦ 3.0.

  The measuring method of the substitution degree of an acyl group can be measured according to ASTM-D817-96.

  The number average molecular weight of the cellulose ester used in the present invention is preferably in the range of 60,000 to 300,000 because the mechanical strength of the resulting film is strong. Furthermore, the thing of 70000-200000 is used preferably.

  The weight average molecular weight Mw and number average molecular weight Mn of the cellulose ester were measured using gel permeation chromatography (GPC).

  The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) Mw = 100000 to 500 calibration curves with 13 samples were used. Thirteen samples are used at approximately equal intervals.

  The cellulose ester such as cellulose acetate phthalate of the present invention can be produced by a known method. Specifically, it can be synthesized with reference to the method described in JP-A-10-45804.

<Ultraviolet absorber>
Although the ultraviolet absorber used in the present invention is not particularly limited, for example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, triazine compounds, nickel complex compounds, inorganic powders Examples include the body.

  For example, 5-chloro-2- (3,5-di-sec-butyl-2-hydroxylphenyl) -2H-benzotriazole, (2-2H-benzotriazol-2-yl) -6- (linear and side Chain dodecyl) -4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, and the like, and tinuvin 928 (U1), tinuvin 900 (U2), tinuvin 109 (U3), tinuvin 400 (U4), Tinuvin 171, Tinuvin 234, Tinuvin 326, Tinuvin 327 (U5), Tinuvin 328 (U6), etc., are all commercially available from Ciba Specialty Chemicals. it can.

  The UV absorbers preferably used in the present invention are benzotriazole UV absorbers, benzophenone UV absorbers, and triazine UV absorbers, particularly preferably benzotriazole UV absorbers and benzophenone UV absorbers. .

  In addition, a discotic compound such as a compound having a 1,3,5 triazine ring is also preferably used as the ultraviolet absorber.

  The cellulose ester film of the present invention preferably contains two or more ultraviolet absorbers.

  As the UV absorber, a polymer UV absorber can also be preferably used, and in particular, a polymer type UV absorber described in JP-A-6-148430 is preferably used.

  The amount of UV absorber used is not uniform depending on the type of UV absorber, usage conditions, etc., but when the dry film thickness of the cellulose ester film is 30 to 200 μm, 0.5 to 10 mass relative to the cellulose ester. % Is preferable, and 0.6 to 4% by mass is more preferable.

<Plasticizer>
The plasticizer of the present invention is not particularly limited, but preferably a polycarboxylic acid ester plasticizer, a glycolate plasticizer, a phthalate ester plasticizer, a fatty acid ester plasticizer, and a polyhydric alcohol ester plasticizer, It is selected from polyester plasticizers, acrylic plasticizers and the like.

  Of these, when two or more plasticizers are used, at least one plasticizer is preferably a polyhydric alcohol ester plasticizer.

  The polyhydric alcohol ester plasticizer is a plasticizer comprising an ester of a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule. Preferably it is a 2-20 valent aliphatic polyhydric alcohol ester.

  In order to lower the melting temperature of the film constituent material, it can be achieved by adding a plasticizer having a melting point or glass transition temperature lower than the glass transition temperature of the cellulose ester.

  The cellulose ester film of the present invention preferably contains 1 to 25% by mass of an ester compound having a molecular weight of 350 to 1500, preferably 400 to 1000, having a structure in which an organic acid and a trivalent or higher alcohol are condensed. By adding 1% by mass or more, the effect of improving the flatness is recognized, and when it is less than 25% by mass, bleeding out is difficult and the temporal stability of the film is excellent, which is preferable.

  The organic acid in the ester compound having a structure in which the organic acid of the present invention and a trivalent or higher-valent alcohol are condensed is represented by the following general formula (1).

In the formula, R _{1 to} R ₅ represent a hydrogen atom or a cycloalkyl group, an aralkyl group, an alkoxy group, a cycloalkoxy group, an aryloxy group, an aralkyloxy group, an acyl group, a carbonyloxy group, an oxycarbonyl group, or an oxycarbonyloxy group. These may be further substituted. L represents a linking group and represents a substituted or unsubstituted alkylene group, an oxygen atom, or a direct bond.

The cycloalkyl group represented by R _{1 to} R ₅ is preferably a cycloalkyl group having 3 to 8 carbon atoms, and specifically, a group such as cyclopropyl, cyclopentyl, cyclohexyl and the like. These groups may be substituted, and preferred substituents include halogen atoms such as chlorine atom, bromine atom, fluorine atom, hydroxyl group, alkyl group, alkoxy group, cycloalkoxy group, aralkyl group (this phenyl group). The group may be further substituted with an alkyl group or a halogen atom), an alkenyl group such as a vinyl group or an allyl group, or a phenyl group (this phenyl group may be further substituted with an alkyl group or a halogen atom). Phenoxy group (this phenyl group may be further substituted by an alkyl group or a halogen atom), an acyl group having 2 to 8 carbon atoms such as an acetyl group or a propionyl group, an acetyloxy group, or a propionyloxy group. And an unsubstituted carbonyloxy group having 2 to 8 carbon atoms such as a group.

The aralkyl group represented by R _{1 to} R ₅ represents a group such as a benzyl group, a phenethyl group, and a γ-phenylpropyl group, and these groups may be substituted. Preferred substituents include The group which may be substituted with the said cycloalkyl group can be mentioned similarly.

Examples of the alkoxy group represented by R _{1 to} R ₅ include an alkoxy group having 1 to 8 carbon atoms, specifically, methoxy, ethoxy, n-propoxy, n-butoxy, n-octyloxy, isopropoxy. , Alkoxy groups such as isobutoxy, 2-ethylhexyloxy, or t-butoxy.

  These groups may be substituted, and preferred substituents include halogen atoms such as chlorine atom, bromine atom, fluorine atom, hydroxyl group, alkoxy group, cycloalkoxy group, aralkyl group (this phenyl group). May be substituted with an alkyl group or a halogen atom), an alkenyl group, a phenyl group (this phenyl group may be further substituted with an alkyl group or a halogen atom), an aryloxy group (for example, phenoxy) An acyl group such as an acetyl group or a propionyl group, or an aryl group such as an acetyloxy group or a propionyloxy group (the phenyl group may be further substituted with an alkyl group or a halogen atom). Arylcarbonyl groups such as unsubstituted acyloxy groups and benzoyloxy groups Shi group.

Examples of the cycloalkoxy group represented by R _{1 to} R ₅ include an unsubstituted cycloalkoxy group having 1 to 8 carbon atoms, specifically, cyclopropyloxy, cyclopentyloxy, cyclohexyl. And groups such as oxy.

  In addition, these groups may be substituted, and preferred substituents include the same groups that may be substituted with the cycloalkyl group.

Examples of the aryloxy group represented by R _{1 to} R ₅ include a phenoxy group, and the phenyl group includes a substituent that is exemplified as a group that may be substituted with the cycloalkyl group such as an alkyl group or a halogen atom. May be substituted.

Examples of the aralkyloxy group represented by R _{1 to} R ₅ include a benzyloxy group, a phenethyloxy group, and the like. These substituents may be further substituted. Preferred substituents include the above-mentioned cycloalkyl. The group which may be substituted with a group can be mentioned similarly.

Examples of the acyl group represented by R _{1 to} R ₅ include an unsubstituted acyl group having 2 to 8 carbon atoms such as an acetyl group and a propionyl group (the hydrocarbon group of the acyl group includes alkyl, alkenyl, alkynyl). These substituents may be further substituted, and preferred substituents include the same groups that may be substituted with the cycloalkyl group.

The carbonyloxy group represented by R _{1 to} R ₅ is an unsubstituted acyloxy group having 2 to 8 carbon atoms such as acetyloxy group and propionyloxy group (the hydrocarbon group of the acyl group is alkyl, alkenyl, alkynyl). And arylcarbonyloxy groups such as a benzoyloxy group, and these groups may be further substituted with the same groups as those which may be substituted with the cycloalkyl group.

The oxycarbonyl group represented by R _{1 to} R ₅ represents an alkoxycarbonyl group such as a methoxycarbonyl group, an ethoxycarbonyl group or a propyloxycarbonyl group, or an aryloxycarbonyl group such as a phenoxycarbonyl group.

  These substituents may be further substituted, and preferred examples of the substituent include the same groups that may be substituted with the cycloalkyl group.

The oxycarbonyloxy group represented by R _{1 to} R ₅ represents a C 1-8 alkoxycarbonyloxy group such as a methoxycarbonyloxy group, and these substituents may be further substituted and are preferably substituted. Examples of the group include the same groups that may be substituted on the cycloalkyl group.

Any one of R _{1 to} R ₅ may be connected to each other to form a ring structure.

The linking group represented by L represents a substituted or unsubstituted alkylene group, an oxygen atom, or a direct bond, and the alkylene group is a group such as a methylene group, an ethylene group, or a propylene group. These groups may be further substituted with the groups mentioned as the groups that may be substituted with the groups represented by R _{1 to} R ₅ .

  Among these, a direct bond and an aromatic carboxylic acid are particularly preferable as the linking group represented by L.

In addition, the organic acid represented by the general formula (1) constituting the ester compound serving as a plasticizer in the present invention includes at least R ₁ or R ₂ having the alkoxy group, acyl group, oxycarbonyl group, carbonyl group. Those having an oxy group or an oxycarbonyloxy group are preferred. A compound having a plurality of substituents is also preferred.

  In the present invention, the organic acid for substituting the hydroxyl group of the trivalent or higher alcohol may be a single type or a plurality of types.

  In the present invention, the trihydric or higher alcohol compound that reacts with the organic acid represented by the general formula (1) to form a polyhydric alcohol ester compound is preferably a 3-20 valent aliphatic polyhydric alcohol. In the present invention, the trihydric or higher alcohol is preferably represented by the following general formula (3).

Formula (3) R '-(OH) m
In the formula, R ′ represents an m-valent organic group, m represents a positive integer of 3 or more, and the OH group represents an alcoholic hydroxyl group. Particularly preferred is a polyhydric alcohol having 3 or 4 as m.

  Examples of preferred polyhydric alcohols include the following, but the present invention is not limited to these.

  Adonitol, arabitol, 1,2,4-butanetriol, 1,2,3-hexanetriol, 1,2,6-hexanetriol, glycerin, diglycerin, erythritol, pentaerythritol, dipentaerythritol, tripentaerythritol, ga Examples include lactitol, inositol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, and xylitol.

  In particular, glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol are preferable.

  The ester of the organic acid represented by the general formula (1) and a trihydric or higher polyhydric alcohol can be synthesized by a known method. In the examples, typical synthesis examples are shown. A method of condensing an organic acid represented by the general formula (1) and a polyhydric alcohol in the presence of an acid, for example, There are a method of reacting with a polyhydric alcohol by leaving it as a chloride or an acid anhydride, a method of reacting a phenyl ester of an organic acid with a polyhydric alcohol, etc., and a method with a good yield is appropriately selected according to the target ester compound. It is preferable.

  As the plasticizer comprising an organic acid represented by the general formula (1) and an ester of a trihydric or higher polyhydric alcohol, a compound represented by the following general formula (2) is preferable.

In the formula, R _{6 to} R ₂₀ represent a hydrogen atom or a cycloalkyl group, an aralkyl group, an alkoxy group, a cycloalkoxy group, an aryloxy group, an aralkyloxy group, an acyl group, a carbonyloxy group, an oxycarbonyl group, or an oxycarbonyloxy group. These may be further substituted. R ₂₁ represents a hydrogen atom or an alkyl group.

The cycloalkyl group, aralkyl group, alkoxy group, cycloalkoxy group, aryloxy group, aralkyloxy group, acyl group, carbonyloxy group, oxycarbonyl group, and oxycarbonyloxy group of R _{6 to} R ₂₀ are represented by the above general formula ( The same group as R < ₁ > -R < ₅ > of 1) is mentioned.

  Below, the specific compound of the polyhydric alcohol ester concerning this invention is illustrated.

  Other plasticizers that can be used in the present invention are not particularly limited, but are preferably polycarboxylic acid ester plasticizers, glycolate plasticizers, phthalate ester plasticizers, fatty acid ester plasticizers, It is selected from polyester plasticizers and acrylic plasticizers.

  Among them, when two or more kinds of plasticizers are used, at least one kind is preferably a polyhydric alcohol ester plasticizer having a molecular weight of 350 to 1500 having a structure in which an organic acid and a trivalent or higher alcohol are condensed.

<Other additives>
The cellulose ester film of the present invention preferably contains the following additives in addition to the ultraviolet absorber and the plasticizer.

(Antioxidant, thermal degradation inhibitor)
In the present invention, conventionally known antioxidants and thermal deterioration inhibitors can be used. In particular, lactone, sulfur, phenol, double bond, hindered amine, and phosphorus compounds can be preferably used.
For example, those including those commercially available from Ciba Specialty Chemicals under the trade names “IrgafosXP40” and “IrgafosXP60” are preferable.

  As the phenolic compound, those having a 2,6-dialkylphenol structure are preferable, for example, those commercially available under the trade names of Ciba Specialty Chemicals, Inc., “Irganox 1076” and “Irganox 1010”.

  Examples of the phosphorous compounds include Sumitizer GP from Sumitomo Chemical Co., Ltd., ADK STAB PEP-24G from ADEKA Co., Ltd., “ADK STAB PEP-36” and “ADK STAB 3010”, Ciba Specialty Chemicals Co., Ltd. "IRGAFOS P-EPQ" and "GSY-P101" sold by Sakai Chemical Co., Ltd. are preferred.

  The hindered amine compounds are preferably commercially available from Ciba Specialty Chemicals, Inc. under the trade names “Tinuvin 144” and “Tinvin 770”, and from ADEKA, Inc. as “ADK STAB LA-52”.

  As the sulfur-based compound, for example, those commercially available from Sumitomo Chemical Co., Ltd. under the trade names of “Sumilizer TPL-R” and “Sumilizer TP-D” are preferable.

  The above-mentioned double bond type compounds are preferably those commercially available from Sumitomo Chemical Co., Ltd. under the trade names of “Sumilizer GM” and “Sumilizer GS”.

  Furthermore, it is possible to contain a compound having an epoxy group as described in US Pat. No. 4,137,201 as an acid scavenger.

  The amount of these antioxidants and the like to be appropriately added is determined in accordance with the process at the time of recycling, but generally 0.05 to 20% by mass, preferably with respect to the resin as the main raw material of the film Is added in the range of 0.1 to 1% by mass.

  These antioxidants and thermal deterioration inhibitors can obtain a synergistic effect by using several different types of compounds in combination rather than using only one kind. For example, the combined use of lactone, phosphorus, phenol and double bond compounds is preferred.

(Fine particles)
The cellulose ester film according to the present invention preferably contains fine particles.

  As fine particles used in the present invention, examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, and hydrated silicic acid. Mention may be made of calcium, aluminum silicate, magnesium silicate and calcium phosphate.

  Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable.

  The average primary particle diameter of the fine particles is preferably 5 to 400 nm, and more preferably 10 to 300 nm.

  These may be mainly contained as secondary aggregates having a particle size of 0.05 to 0.3 μm, and may be contained as primary particles without being aggregated if the particles have an average particle size of 100 to 400 nm. preferable.

  The content of these fine particles in the polarizing plate protective film is preferably 0.01 to 1% by mass, particularly preferably 0.05 to 0.5% by mass. In the case of a polarizing plate protective film having a multilayer structure by the co-casting method, it is preferable to contain fine particles of this addition amount on the surface.

  Silicon dioxide fine particles are commercially available, for example, under the trade names Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above Nippon Aerosil Co., Ltd.). it can.

  Zirconium oxide fine particles are commercially available, for example, under the trade names Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) and can be used.

  Examples of the polymer include silicone resin, fluororesin, and acrylic resin. Silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120, and 240 (manufactured by Toshiba Silicone Co., Ltd.) It is marketed by name.

  Among these, Aerosil 200V and Aerosil R972V are particularly preferably used because they have a large effect of reducing the friction coefficient while keeping the turbidity of the polarizing plate protective film low. In the polarizing plate protective film used in the present invention, the dynamic friction coefficient of at least one surface is preferably 0.2 to 1.0.

(Sugar ester compound)
The cellulose ester film of the present invention may be formed by melting a melt composition containing a sugar ester compound obtained by esterifying a hydroxyl group of a sugar compound in which 1 to 12 at least one structure selected from a furanose structure and a pyranose structure is bonded. preferable.

  Examples of the sugar compound of the present invention include glucose, galactose, mannose, fructose, xylose, arabinose, lactose, sucrose, cellobiose, cellotriose, maltotriose, raffinose, etc., particularly those having both a furanose structure and a pyranose structure. preferable. An example is sucrose.

  The sugar ester compound of the present invention is one in which part or all of the hydroxyl groups of the sugar compound are esterified or a mixture thereof.

(Acrylic polymer)
In the present invention, in order to adjust the optical properties in addition to the additive, it is preferable to melt and form a molten composition containing an acrylic polymer having a weight average molecular weight of 500 or more and 30000 or less.

  The acrylic polymer of the present invention includes an ethylenically unsaturated monomer Xa that does not have an aromatic ring and a hydrophilic group in the molecule, and an ethylenically unsaturated monomer Xb that does not have an aromatic ring in the molecule and has a hydrophilic group. Polymer X having a weight average molecular weight of 5,000 to 30,000 obtained by copolymerization of

  More preferably, the polymer Y having a weight average molecular weight of 500 or more and 3000 or less obtained by polymerizing an ethylenically unsaturated monomer Ya having no aromatic ring is preferably used.

  The polymer X of the present invention is a copolymer of an ethylenically unsaturated monomer Xa having no aromatic ring and a hydrophilic group in the molecule and an ethylenically unsaturated monomer Xb having no aromatic ring and having a hydrophilic group in the molecule. The polymer having a weight average molecular weight of 5,000 to 30,000.

  Preferably, Xa is an acrylic or methacrylic monomer that does not have an aromatic ring and a hydrophilic group in the molecule, and Xb is an acrylic or methacrylic monomer that does not have an aromatic ring in the molecule and has a hydrophilic group.

  In the present invention, the number average molecular weight and the weight average molecular weight were measured using high performance liquid chromatography. The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 100000 to 500 samples were used. Thirteen samples are used at approximately equal intervals.
<Melt casting film formation of cellulose ester film>
The method for producing a cellulose ester film of the present invention is a method for producing a cellulose ester film in which at least a cellulose ester, an ultraviolet absorber and a plasticizer are mixed and melted, extruded from a die, and cast onto a cooling roll. Means for supplying heated gas to the outlet; means for exhausting the gas; means for cooling the exhausted gas and separating the compound contained in the exhausted gas from the gas; and means for recovering the separated compound; It is characterized by having.

  The entire manufacturing method will be described below.

<Melted pellet manufacturing process>
The mixture of cellulose ester, ultraviolet absorber, plasticizer and other additives used for melt extrusion is usually preferably kneaded in advance and pelletized.

  Pelletization may be performed by a known method. For example, dry cellulose ester, plasticizer, and other additives are fed to an extruder using a feeder and kneaded using a single-screw or twin-screw extruder, and then formed into a strand from a die. It can be done by extrusion, water cooling or air cooling and cutting.

  It is important to dry the raw material before extruding to prevent decomposition of the raw material. In particular, since the cellulose ester easily absorbs moisture, it is preferable to dry it at 70 to 140 ° C. for 3 hours or more with a dehumidifying hot air dryer or a vacuum dryer, and to keep the moisture content at 200 ppm or less, and further 100 ppm or less.

  The additives may be mixed before being supplied to the extruder, or may be supplied by individual feeders. A small amount of an additive such as an antioxidant is preferably mixed in advance in order to mix uniformly.

  Mixing of the antioxidants may be performed by mixing solids, and if necessary, the antioxidant may be dissolved in a solvent, impregnated with cellulose ester and mixed, or sprayed and mixed. Also good.

  A vacuum nauter mixer or the like is preferable because drying and mixing can be performed simultaneously. Moreover, when touching with air, such as an exit from a feeder part or die | dye, it is preferable to set it as atmosphere, such as dehumidified air and dehumidified N2 gas.

  The extruder is preferably processed at as low a temperature as possible so that the shearing force is suppressed and the resin can be pelletized so as not to deteriorate (molecular weight reduction, coloring, gel formation, etc.). For example, in the case of a twin screw extruder, it is preferable to rotate in the same direction using a deep groove type screw. From the uniformity of kneading, the meshing type is preferable.

  A film is formed using the pellets obtained as described above. It is also possible to feed the raw material powder as it is with a feeder to an extruder without forming into a pellet and form a film as it is.

<Process for extruding molten mixture from die to cooling roll>
Using a single-screw or twin-screw type extruder, the melt temperature Tm during extrusion is about 200-300 ° C, filtered through a leaf disk filter, etc. Cast on the cooling roll, solidify on the cooling roll, and cast while pressing with the elastic touch roll.

  When introducing from the supply hopper to the extruder, it is preferable to prevent oxidative decomposition or the like under vacuum or reduced pressure or in an inert gas atmosphere. Tm is the temperature at the die exit portion of the extruder.

  When foreign matter such as scratches or plasticizer aggregates adheres to the die, streak-like defects may occur. Such defects are also referred to as die lines, but in order to reduce surface defects such as die lines, it is preferable to have a structure in which the resin retention portion is minimized in the piping from the extruder to the die. . It is preferable to use a die that has as few scratches as possible inside the lip.

  The inner surface that contacts the molten resin such as an extruder or a die is preferably subjected to surface treatment that makes it difficult for the molten resin to adhere to the surface by reducing the surface roughness or using a material having a low surface energy. Specifically, a hard chrome plated or ceramic sprayed material is polished so that the surface roughness is 0.2 S or less.

  The cooling roll of the present invention is not particularly limited, but is a roll having a structure with a high-rigidity metal roll that allows a temperature-controllable heat medium or refrigerant to flow inside, and is not limited in size. It is sufficient that the film is large enough to cool the formed film, and the diameter of the cooling roll is usually about 100 mm to 1 m.

  Examples of the surface material of the cooling roll include carbon steel, stainless steel, aluminum, and titanium. Further, in order to increase the surface hardness or improve the releasability from the resin, it is preferable to perform a surface treatment such as hard chrome plating, nickel plating, amorphous chrome plating, or ceramic spraying.

  The surface roughness of the surface of the cooling roll is preferably 0.1 μm or less in terms of Ra, and more preferably 0.05 μm or less. The smoother the roll surface, the smoother the surface of the resulting film. Of course, it is preferable to further polish the surface that has been subjected to surface processing so as to have the surface roughness described above.

  Examples of the elastic touch roll of the present invention include JP-A-03-124425, JP-A-08-224772, JP-A-07-1000096, JP-A-10-272676, WO97-028950, JP-A-11-235747, JP-A-11-235747. Although the surface as described in 2002-36332, Unexamined-Japanese-Patent No. 2005-172940, or Unexamined-Japanese-Patent No. 2005-280217 can use a thin-film metal sleeve covering silicone rubber roll, it is the following elastic touch rolls. preferable.

  When peeling the film from the cooling roll, it is preferable to control the tension to prevent deformation of the film.

<< Means for supplying heated gas to die outlet, means for exhausting the gas >>
The manufacturing method of the present invention includes means for supplying a heated gas near the die discharge port and means for exhausting the gas.

  The gas supplied to the die discharge port blows off an additive such as a plasticizer that volatilizes in the vicinity of the die from the vicinity of the die and prevents the additive from condensing at the die discharge port. And the gas containing the volatilized additive is conveyed from the position to the collection zone by the exhaust means.

  As means for supplying the heated gas in the vicinity of the die discharge port, an apparatus described in JP-A-11-115033 can be preferably used. The gas to be supplied may be air or water vapor, but a mixture of both is most preferred. Further, from the viewpoint of preventing thermal deterioration, an inert gas such as nitrogen or argon may be supplied.

  It is preferable from the viewpoint of uneven retardation that the gas temperature is heated in the range of Tm-50 ° C to Tm ° C.

  If it is lower than this range, retardation unevenness due to cooling of the web tends to occur, and if it is excessive, the film is broken. On the other hand, when it is higher than this range, the flatness is deteriorated by heating the web, and the retardation unevenness is easily caused by the correction of the touch roll.

  As a means for exhausting the gas, normal vacuum suction is preferable. The supply and exhaust directions are preferably supplied from the side far from the die and exhausted from the side close to the die.

Gas, it is preferable that the it is preferred to supply at 0.01 to 50 m ³ / min, 0.01 to 50 m ³ / min is nearly as the amount of gas is also supplied exhaust.

<< Means for separating the compound contained in the exhausted gas by cooling the exhausted gas >>
The gas exhausted in the present invention is cooled by the cooling means of the present invention. The path leading from the exhaust to the cooling is preferably maintained at a temperature of Tm-50 to Tm ° C. so that the condensate is generated and deposited and is not blocked.

  The cooling means of the present invention is preferably a cooling medium that maintains a temperature of Tm-200 to Tm-100 ° C. from the viewpoint of recovery efficiency, and a rotating drum, a cooling fin, a simple cooling pipe, etc. can be used. A rotating drum in which a cooling medium such as the like circulates is preferable.

  It is also preferable to use adiabatic expansion in order to promote the condensation. For example, a method of gradually reducing the diameter of a tube for inducing a gas containing volatile matter and spraying it on the surface of the rotating drum in the form of a nozzle can be preferably applied.

  Volatilized plasticizer and the like contained in the exhausted gas condenses on the cooling rotating drum and is separated from the gas.

  The rotating drum can be made of the same surface material as the cooling drum described above. The conditions such as the diameter, the rotation speed, and the drum temperature can be appropriately determined in relation to the casting speed.

<Means for recovering separated compounds>
In the present invention, the aggregate is periodically removed and collected. When a rotating drum is used, a method of scraping against the blade is preferable.

  The blade is not particularly limited as long as it can be used for cleaning a rotating body such as a drum, a roll, and a belt. For example, a cleaning blade made of polyurethane or the like for scraping off toner on a photosensitive drum of an electrophotographic copying machine is used. can do.

  When a rotating drum is not used, there is a method of periodically taking out the cooling medium and collecting the condensate, or by periodically heating the cooling medium to melt the condensate and recovering it as a liquid by natural fall. Though conceivable, in order to cope with continuous production for a long time, a method of continuously collecting with a rotating drum is preferable.

  It is preferable to reuse the recovered aggregate as a raw material. The agglomerated product obtained in the present invention is mainly an ultraviolet absorber and a plasticizer, but is mixed with cellulose ester to melt, volatilize and recover, so that bleed out from the cellulose ester film can be achieved compared to the original additive. Excellent performance to reduce.

  Although this mechanism is not clear, it is presumed that a new compound produced through moderate thermal deterioration and vaporization / condensation of the present invention has some effect.

  The present invention will be described with reference to FIG.

  A mixed melt 1 in which cellulose ester, an ultraviolet absorber, a plasticizer, and the like are mixed is extruded from a die 2. A gas 3 heated by a heater 8 is supplied near the discharge port of the die. And the gas 4-1 containing the plasticizer volatilized in the vicinity of the die discharge port is sucked and exhausted from the vicinity of the die discharge port.

  The exhausted gas is cooled by coming into contact with the cooled rotating drum 5, and the volatile matter contained in the gas is condensed on the surface of the rotating drum 5, separated from the gas, and the gas 4- 2 is reused.

  The plasticizer or the like condensed on the surface of the rotating drum 5 becomes a recovered material 7 that is scraped off by the blade 6 adjacent to the rotating drum. This 7 will be reused.

<Extension process>
In the present invention, it is preferred that the film obtained as described above is further stretched by 1.01 to 3.0 times in at least one direction after passing through the step of contacting the cooling roll. The sharpness of the streaks becomes gentle by stretching and can be highly corrected.

  Preferably, the film is stretched 1.1 to 2.0 times in both the longitudinal (film transport direction) and lateral (width direction) directions.

  As a method of stretching, a known roll stretching machine or tenter can be preferably used. In particular, when the polarizing plate protective film is a retardation film, it is preferable to make the stretching direction the width direction because lamination with the polarizing film can be performed in a roll form.

  By stretching in the width direction, the slow axis of the optical film made of the polymer film becomes the width direction. On the other hand, the transmission axis of the polarizing film is also usually in the width direction. A good viewing angle can be obtained by incorporating in a liquid crystal display device a polarizing plate laminated so that the transmission axis of the polarizing film and the slow axis of the polarizing plate protective film are parallel to each other.

  When the cellulose ester film of the present invention is used as a film having an optical compensation function, the temperature and magnification can be selected so that desired retardation characteristics can be obtained.

  Usually, the draw ratio is 1.1 to 3.0 times, preferably 1.2 to 1.5 times, and the drawing temperature is usually Tg to Tg + 50 ° C. of the resin constituting the film, preferably Tg to Tg + 40 ° C. In the temperature range.

  The stretching is preferably performed under a uniform temperature distribution controlled in the width direction. The temperature is preferably within ± 2 ° C, more preferably within ± 1 ° C, and particularly preferably within ± 0.5 ° C.

  For the purpose of reducing the retardation of the cellulose ester film produced by the above method and reducing the dimensional change rate, the film may be contracted in the longitudinal direction or the width direction.

  In order to shrink in the longitudinal direction, for example, there is a method in which the film is shrunk by temporarily clipping out the width stretching and relaxing in the longitudinal direction, or by gradually narrowing the interval between adjacent clips of the transverse stretching machine.

  The in-plane retardation (Ro) and thickness direction retardation (Rt) of the cellulose ester film of the present invention can be adjusted as appropriate, but when having a retardation function, Ro is 20 to 200 nm, and Rt is 90 to 400 nm. The ratio Rt / Ro of Rt and Ro is preferably 0.5 to 4, particularly preferably 1 to 3.

In addition, when the refractive index Nx in the slow axis direction of the film, the refractive index Ny in the fast axis direction, the refractive index Nz in the thickness direction, and the film thickness of the film are d (nm),
Ro = (Nx−Ny) × d
Rt = {(Nx + Ny) / 2−Nz} × d
Represented as: (Measurement wavelength 590nm)
The variation in retardation is preferably as small as possible, and is usually within ± 10 nm, preferably ± 5 nm or less, more preferably ± 2 nm or less.

  Uniformity in the slow axis direction is also important, and the angle is preferably −5 to + 5 °, more preferably in the range of −1 to + 1 °, particularly −0. It is preferably in the range of 5 to + 0.5 °, particularly preferably in the range of −0.1 to + 0.1 °. These variations can be achieved by optimizing the stretching conditions.

  In the cellulose ester film of the present invention, it is preferable that the height from the top of the adjacent mountain to the bottom of the valley is 300 nm or more, and there is no streak continuous in the longitudinal direction with an inclination of 300 nm / mm or more.

  The shape of the streak was measured using a surface roughness meter. Specifically, using a Mitutoyo SV-3100S4, a stylus (diamond needle) having a tip shape of a cone of 60 ° and a tip curvature radius of 2 μm was used. The film is scanned in the width direction of the film at a measurement speed of 1.0 mm / sec while applying a load of 0.75 mN, and a cross-sectional curve is measured with a Z-axis (thickness direction) resolution of 0.001 μm.

From this curve, the streak height reads the vertical distance (H) from the top of the mountain to the bottom of the valley. The slope of the streak is obtained by reading the horizontal distance (L) from the top of the mountain to the bottom of the valley and dividing the vertical distance (H) by the horizontal distance (L).
<Cleaning equipment>
It is preferable to add an apparatus for automatically cleaning the belt and the roll to the manufacturing apparatus of the present invention. There is no particular limitation on the cleaning device, but for example, a method of niping a brush roll, a water absorbing roll, an adhesive roll, a wiping roll, etc., an air blow method of blowing clean air, a laser incinerator, or a combination thereof is there.

  In the case where the cleaning roll is nipped, the cleaning effect is great if the belt linear velocity and the roller linear velocity are changed.

The present invention will be specifically described below with reference to examples.
Example 1
The effect of the present invention was examined for a cellulose ester film production process having the following composition.

Cellulose acetate propionate 100 parts by mass (dried at 80 ° C. for 6 hours (water content 200 ppm), acetyl group substitution degree 1.30, propionyl group substitution degree 1.23, number average molecular weight 60000)
Plasticizer Table 1 UV absorber Table 1 Irganox 1010 0.5 parts by mass (Ciba Specialty Chemicals Co., Ltd.)
IrgafosP-EPQ 0.3 part by mass (manufactured by Ciba Specialty Chemicals)
Sumilizer GS 0.2 parts by mass (manufactured by Sumitomo Chemical Co., Ltd.)
Seahoster KEP-30 0.1 part by mass (manufactured by Nippon Shokubai Co., Ltd.)
The above mixture was further dried while mixing at 80 ° C. and 1 Torr for 3 hours in a vacuum nauter mixer.

  The obtained mixture was melt-mixed at 235 ° C. using a twin-screw extruder and pelletized. At this time, an all screw type screw was used to suppress heat generation due to shearing during kneading.

  In addition, evacuation was performed from the vent hole, and volatile components generated during kneading were removed by suction. The space between the feeder and hopper supplied to the extruder, the extruder die and the cooling tank was a dry nitrogen gas atmosphere to prevent moisture from being absorbed into the resin.

  Next, the manufacturing apparatus shown in FIG. 1 was continuously operated using the obtained pellets, and the state of volatile substances condensed around the die and in the piping was observed.

The supply amount of the heated gas was 10 m ³ / min (air took in the outside air as it was, water vapor was 30% by volume of the gas supply amount), and the exhaust amount was also 10 m ³ / min. As the rotating drum for cooling, a surface having an average diameter of 500 mm made of stainless steel was viewed in the direction of the arrow at 5 rpm per minute.

  As the blade, a polyurethane cleaning blade (manufactured by Tokai Rubber Industries, Ltd.) was used. The observation time was 12 hours, 24 hours and 48 hours from the start of operation.

  For comparison, a case where heated gas was not supplied (sample No. 1) and a case where volatiles were not separated from the exhausted gas by cooling (sample Nos. 2 and 3) were examined.

P1: Compound 61 represented by the general formula (2)
P2: Same as compound 65
P3: Same as compound 62
P4: Same as compound 54
P5: Same as compound 64
P6: Same as compound 63
<Die condition>
0 Nothing around the die.

  1 Some adhesion is seen around the die.

  2 The deposit around the die is noticeable and deposited.

  3 Deposits around the die are falling.

<Piping condition>
0 Nothing is attached to the piping.

  1 Some adhesion is observed on the piping.

  2 Piping was noticeably attached and the exhaust capacity was reduced by 10% or more.

  3 The piping is clogged.

  The results are shown in Table 1.

  Experiment No. For No. 11, there was no problem of process contamination, but the retardation unevenness of the finished film was larger than other levels.

Example 2
The manufacturing procedure of the cellulose ester film 2-1 having the following composition will be described.

Cellulose acetate propionate 100 parts by mass (dried at 80 ° C. for 6 hours (water content 200 ppm), acetyl group substitution degree 1.30, propionyl group substitution degree 1.23, number average molecular weight 60000)
P1 10 parts by mass U1 3.0 parts by mass Irganox 1010 0.5 parts by mass (manufactured by Ciba Specialty Chemicals)
IrgafosP-EPQ 0.3 part by mass (manufactured by Ciba Specialty Chemicals)
Sumilizer GS 0.2 parts by mass (manufactured by Sumitomo Chemical Co., Ltd.)
Seahoster KEP-30 0.1 part by mass (manufactured by Nippon Shokubai Co., Ltd.)
The above mixture was further dried while mixing at 80 ° C. and 1 Torr for 3 hours in a vacuum nauter mixer.

  The obtained mixture was melt-mixed at 235 ° C. using a twin-screw extruder and pelletized. At this time, an all screw type screw was used to suppress heat generation due to shearing during kneading.

  In addition, evacuation was performed from the vent hole, and volatile components generated during kneading were removed by suction. The space between the feeder and hopper supplied to the extruder, the extruder die and the cooling tank was a dry nitrogen gas atmosphere to prevent moisture from being absorbed into the resin.

  The cellulose ester film containing the recovered compound was formed using the manufacturing apparatus shown in FIG.

  The first cooling roll and the second cooling roll were made of stainless steel having a diameter of 40 cm, and the surface was hard chrome plated. In addition, temperature adjusting oil (cooling fluid) was circulated inside to control the roll surface temperature.

  The elastic touch roll had a diameter of 20 cm, the inner cylinder and the outer cylinder were made of stainless steel, and the surface of the outer cylinder was hard chrome plated. The wall thickness of the outer cylinder was 2 mm, and oil for cooling (cooling fluid) was circulated in the space between the inner cylinder and the outer cylinder to control the surface temperature of the elastic touch roll.

  Pellets (water content 50 ppm) were melt extruded from a T die onto a first cooling roll having a surface temperature Tr1 of 120 ° C. at a melting temperature Tm using a single screw extruder to obtain a cast film having a thickness of 220 μm.

  At this time, a T die having a lip clearance of 1.5 mm and an average surface roughness Ra of 0.01 μm was used. Further, an elastic touch roll having a 2 mm thick metal surface was pressed on the first cooling roll at a linear pressure of 10 kg / cm.

The film temperature on the touch roll side during pressing was 230 ° C. ± 1 ° C. (The film temperature on the touch roll side at the time of pressing here refers to the temperature of the film at the position where the touch roll on the first roll (cooling roll) is in contact with the non-contact thermometer by retreating the touch roll. (This refers to the average value of the film surface temperature measured at 10 points in the width direction from a position 50 cm away without a roll.)
The glass transition temperature Tg of this film was 136 ° C.

  The surface temperature Tr0 of the elastic touch roll was 120 ° C., and the surface temperature Tr2 of the second cooling roll was 120 ° C.

  The obtained film was first stretched 1.6 times in the transport direction at 160 ° C. by a stretching machine utilizing the difference in peripheral speed of the roll. Next, it is introduced into a tenter having a preheating zone, a stretching zone, a holding zone, and a cooling zone (there is also a neutral zone for ensuring thermal insulation between the zones). After stretching 7 times, the film was cooled to 30 ° C. while relaxing 2% in the width direction, then released from the clip, and the clip gripping part was cut off to obtain a cellulose ester film 2-1 having a thickness of 80 μm.

  At this time, the preheating temperature and the holding temperature were adjusted to prevent the bowing phenomenon due to stretching.

  In the same manner as the cellulose ester film 2-1, cellulose ester films 2-2 to 2-16 were produced. However, the recovered material obtained in Example 1 was added as shown in Table 2.

  The compound continuously volatilized under each experimental condition of Example 1 is recovered, and the plasticizer and ultraviolet absorber contained in the recovered compound are quantified by liquid chromatography in which a calibration curve has been prepared in advance. As shown in Table 2, the final amount of plasticizer: UV absorber = 10: 3.

  About the obtained cellulose-ester films 2-1 to 2-16, the bleed-out was evaluated by the following method. The results are shown in Table 2.

<Bleed-out value>
A film sample was cut out in a size of 10 cm in the width direction and 10 cm in the longitudinal direction, treated for 48 hours under the conditions of 80 ° C. and 90% RH, and then TURBIDITY METER T-2600DA manufactured by Tokyo Denshoku Co., Ltd. The haze value measured using this was taken as the bleed-out value.

  The bleed-out of the cellulose ester film containing the recovered product of the present invention was reduced.

Claims (4)

  In a method for producing a cellulose ester film in which at least a cellulose ester, an ultraviolet absorber and a plasticizer are mixed and melted, extruded from a die, and cast on a cooling roll, a means for supplying heated gas to a die discharge port, A method for producing a cellulose ester film, comprising: means for exhausting, means for cooling the exhausted gas and separating a compound contained in the exhausted gas from the gas, and means for recovering the separated compound .   2. The method for producing a cellulose ester film according to claim 1, wherein the means for cooling the exhausted gas and separating the compound contained in the exhausted gas from the gas is a rotating drum.   The method for producing a cellulose ester film according to claim 1 or 2, wherein the means for recovering the separated compound is a blade adjacent to the rotating drum.   A cellulose ester film comprising at least a cellulose ester, an ultraviolet absorber and a plasticizer, wherein the cellulose ester film contains the recovered compound according to any one of claims 1 to 3. .