JP6744745B2 - Thermoplastic resin composition and method for producing optical film comprising thermoplastic resin composition - Google Patents

Description

The present invention relates to a thermoplastic resin composition and a method for producing an optical film made of the thermoplastic resin composition.

Optical transparency and optical homogeneity are required for a plastic film used in a device that handles polarized light such as a liquid crystal display device. Therefore, a polarizer protective film for protecting a polarizer or an optical film typified by a film substrate for a liquid crystal display device is required to have a small retardation represented by the product of birefringence and thickness. In addition, it is particularly required that the image distortion phenomenon due to the so-called lens effect due to the unevenness of the film surface is unlikely to occur. Therefore, when there are significant irregularities due to foreign substances in the film and the surface quality of the film deteriorates, when used as an optical film, there is a problem such as a color loss phenomenon such as partial color fading, or a problem such as image distortion. Will occur.

Acrylic resin films have excellent optical transparency and have been used in the optical film field in recent years, but they have the drawbacks of low film strength and toughness, low film moldability, and low transportability. With respect to these drawbacks, by adding a rubber-like polymer to an acrylic resin, a film made of an acrylic resin composition having improved strength and toughness while maintaining excellent transparency peculiar to the acrylic resin is obtained. Is possible.

In Patent Document 1, stress whitening is small, surface hardness is high, transparency is excellent, weather resistance is excellent, tensile elongation at break is large, cracks hardly occur when the film is cut, and moldability and surface property are also excellent. Also disclosed is a film obtained from a resin composition comprising a multi-layered acrylic polymer using a specific acrylic ester rubber polymer and a methacrylic polymer. Further, in Patent Document 2, a methacrylic resin composition having a specific layer structure and particle size, which is excellent in transparency, weather resistance, hardness and impact resistance, and is also excellent in bending crack resistance and moldability. Films obtained from objects are disclosed.

As a method for producing such a rubbery polymer-containing acrylic resin composition film, in addition to the solvent casting method generally used for various optical films, from the viewpoint of excellent productivity, work environment, etc., a melt extrusion method is used. Is preferably used. Particularly, when the rubbery polymer-containing acrylic resin composition film is used as an optical film, after removing the foreign matter in the composition by filtering the rubbery polymer-containing acrylic resin composition with a polymer filter during film production. It is formed into a film.

JP, 2004-137299, A International Publication No. 2005/095478 JP, 2009-083306, A

In the production of a film made of a thermoplastic resin composition having a filtration step with a polymer filter, foreign substances remaining in the filter are generated in the film obtained by the production for a while after the start of use of the polymer filter. As the foreign substances, there are foreign substances existing in the unused polymer filter such as foreign substances mixed in when the filter element is manufactured or when the filter element is assembled into a polymer filter, and long-term production suspension due to product type change or the like. When production is stopped, it is generally washed and then used for production again. As a result, there are foreign substances remaining in the polymer filter due to poor washing at that time. For example, when the polymer filter used for the production of a resin comprising a mixed system of a rubbery polymer component and a thermoplastic resin component such as a rubbery polymer-containing thermoplastic resin composition is washed and used again for production. The rubber-like polymer component remaining in the polymer filter due to poor cleaning is generated as foreign matter in the film for a while after the start of production. In both cases of the unused polymer filter and the reused polymer filter, when the thermoplastic resin composition is continuously produced, the foreign matter due to the foreign matter remaining in the polymer filter is gradually reduced. It takes a particularly long time to reduce foreign substances to such an extent that it can be used as a film, and during that long time, a film that cannot be used as an optical film is produced, and the production yield is reduced accordingly.

Here, Patent Document 3 discloses, as a cleaning agent for a heating cylinder or a screw of a resin molding machine, a cleaning agent in which a specific polymer containing methyl methacrylate as a main component is blended in a specific composition ratio. There is. However, no consideration is given to production using polymer filters.

The present invention makes it possible to improve the production yield of a thermoplastic resin composition containing a rubber-like polymer after the start of use of an unused or reused polymer filter, a thermoplastic resin containing a rubber-like polymer. It is an object to provide a method for producing a resin composition.

The present inventor has conducted diligent studies on the above problems, and by adjusting the differential pressure condition between the resin pressure at the inlet and the resin pressure at the outlet of the polymer filter, the foreign matter in the polymer filter is efficiently and early discharged. I found that I can do it.

The first of the present invention is a method for producing a thermoplastic resin composition containing a rubber-like polymer component, the thermoplastic resin composition having a step of passing through an extruder and being filtered by a polymer filter. The filtration is carried out at the start of melt extrusion from the extruder at a pressure difference P1 [MPa] between the resin pressure at the inlet and the resin pressure at the outlet of the polymer filter, and the thermoplastic resin composition represented by the following formula (1): After the amount W [kg] of the substance is flown into the polymer filter, the thermoplastic resin composition is mixed with the polymer filter by setting the pressure difference between the resin pressure at the inlet and the resin pressure at the outlet of the polymer filter to P2 [MPa]. And the differential pressures P1 and P2 satisfy the relationship represented by the following formula (2):
The present invention relates to a method for producing a thermoplastic resin composition.
W≧A×B/10 [kg] (1)
A: Diameter of filter element (inch), B: Number of filter elements P1≧8 MPa, and P1>P2 (2)

It is preferable that the resin temperature T1 in the polymer filter at the differential pressure P1 [MPa] and the resin temperature T2 in the polymer filter at the differential pressure P2 [MPa] satisfy the relationship represented by T1≦T2.

It is preferable that the thermoplastic resin constituting the thermoplastic resin composition is an acrylic resin.

The second of the present invention is a method for producing an optical film comprising a thermoplastic resin composition containing a rubbery polymer component, wherein the thermoplastic resin composition passes through an extruder and is filtered by a polymer filter. And a step in which the thermoplastic resin composition is molded after the filtration, wherein the filtration is performed by adjusting the resin pressure at the inlet and the resin pressure at the outlet of the polymer filter at the start of melt extrusion from the extruder. After flowing W [kg] of the amount of the thermoplastic resin composition represented by the following formula (1) into the polymer filter with a differential pressure P1 [MPa], the resin pressure at the inlet and the resin pressure at the outlet of the polymer filter The pressure difference is P2 [MPa], and the thermoplastic resin composition is caused to flow into the polymer filter. The differential pressures P1 and P2 satisfy the relationship represented by the following formula (2). The present invention relates to a method for producing an optical film made of a resin composition.
W≧A×B/10 [kg] (1)
A: Diameter of filter element (inch), B: Number of filter elements P1≧8 MPa, and P1>P2 (2)

It is possible to provide a method for producing a thermoplastic resin composition containing a rubber-like polymer, which makes it possible to improve the production yield after starting the use of an unused or reused polymer filter.

It is a figure which shows typically an example of the apparatus which concerns on the manufacturing method of a thermoplastic resin composition. It is a figure which shows an example of a polymer filter internal structure which concerns on the manufacturing method of a thermoplastic resin composition.

Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments. The method for producing a thermoplastic resin composition of the present invention is a method for producing a thermoplastic resin composition containing a rubbery polymer component, wherein the thermoplastic resin composition passes through an extruder and is filtered by a polymer filter. The filtration is represented by the following formula (1) with a pressure difference P1 [MPa] between the resin pressure at the inlet and the resin pressure at the outlet of the polymer filter at the start of melt extrusion from the extruder. After the amount W [kg] of the thermoplastic resin composition is flown into the polymer filter, the pressure difference between the resin pressure at the inlet and the resin pressure at the outlet of the polymer filter is set to P2 [MPa], and the thermoplastic resin is The method has a step of causing the composition to flow into the polymer filter, and the differential pressures P1 and P2 satisfy the relationship represented by the following formula (2).
W≧A×B/10 [kg] (1)
A: Filter element diameter (inch), B: Number of filter elements P1≧8 MPa, and P1>P2 (2)

FIG. 1 is a diagram schematically showing an example of an apparatus according to a method for producing a thermoplastic resin composition containing a rubbery polymer component of the present invention. A thermoplastic resin composition, which is a raw material of a thermoplastic resin composition containing a rubbery polymer component, is put into an extruder 10, and is heated to a temperature of a glass transition temperature or higher in the extruder 10 to be in a molten state. The molten thermoplastic resin composition moves to the polymer filter 12 via the gear pump 11 attached to the outlet side of the extruder. Then, in the polymer filter 12, foreign matter in the thermoplastic resin composition is filtered, transferred to the die 13 attached to the outlet side of the polymer filter 12, and discharged in a molten state from the die outlet 14 at the tip of the die. .. Depending on the shape of the die outlet, the molten thermoplastic resin composition 15 has a sheet shape.

When the thermoplastic resin composition containing the rubber-like polymer component is filtered by the polymer filter 12, at the start of melt extrusion from the extruder, the differential pressure P1 between the resin pressure at the inlet of the polymer filter 12 and the resin pressure at the outlet thereof. At a pressure of [MPa], a thermoplastic resin composition of an amount W [kg] represented by the following formula (1) is caused to flow into the polymer filter, and then the pressure difference between the resin pressure at the inlet of the polymer filter 12 and the resin pressure at the outlet is adjusted. As P2 [MPa], the thermoplastic resin composition is caused to flow into the polymer filter. The differential pressures P1 and P2 are set to satisfy the relationship represented by the following equation (2).
W≧A×B/10 [kg] (1)
A: Diameter of filter element (inch), B: Number of filter elements P1≧8 MPa, and P1>P2 (2)

Subsequently, the sheet-shaped thermoplastic resin composition 15 discharged from the die outlet 14 is sandwiched between the elastic roll 16 and the cast roll 17 to cool the thermoplastic resin composition 15 to a temperature below its glass transition temperature. By doing so, the film-shaped thermoplastic resin composition 15 such as an optical film can be obtained. The film-shaped thermoplastic resin composition 15 such as an optical film can also be obtained by casting the sheet-shaped thermoplastic resin composition 15 in a molten state on the cast roll 17 without using the elastic roll 16. Can be obtained. The obtained film-shaped thermoplastic resin composition 15 is wound up by a winding machine 19. The sandwich molding step is a step for smoothing the film surface and is different from the step for stretching the film.

Further, the stretching of the film can be carried out while heating the film by using the stretching machine 18, and further, depending on the purpose, biaxial stretching can be carried out and modification such as imparting toughness to the film is also possible. is there.

Although not shown, the thermoplastic resin composition 15 can be formed into a strand shape depending on the shape of the die outlet 14, and pelletized thermoplastic resin composition can be obtained by cooling and solidifying in a water tank and strand cutting with a pelletizer.

[Extruder]
The extruder used in the present invention is not particularly limited, and various extruders can be used, and for example, a single-screw extruder, a twin-screw extruder or a multi-screw extruder can be used. The above-exemplified extruders may be used alone or a plurality of extruders may be connected in series.

The cylinder temperature of the extruder depends on the type of resin contained in the thermoplastic resin composition, but when acrylic resin is used, for example, 150° C. or higher and 310° C. or lower is preferable, and 180° C. or higher and 280° C. or lower is more preferable.

[Polymer filter]
The polymer filter used in the present invention is not particularly limited as long as it can remove foreign matters of the thermoplastic resin composition.

FIG. 2 is a diagram showing an example of the internal structure of the polymer filter. The polymer filter 12 has a structure in which one or more filter elements 21 are stacked. The arrow described in FIG. 2 indicates the flow direction of the molten resin. When the molten resin flows into the polymer filter through the inlet 22, it is filtered by one or more filter elements 21, flows into the filter support 24 that also serves as a flow path, and flows out through the outlet 23.

The polymer filter is composed of one or more filter elements. Examples of the structure of the filter element include a structure in which fiber bundles are twisted together, a mesh structure, a nonwoven fabric structure, and a powder sintered body structure. Among these, the non-woven fabric structure is preferable because the accuracy of removing foreign matters in the resin composition is high.

The shape of the filter element may be, for example, a sheet shape (leaf disk type). In the case of a sheet shape (leaf disk type), a filter support, which also serves as a flow path for the molten resin after foreign matter removal, is laminated in parallel with the axis. Preferably. As the sheet shape (leaf disc type), a circular sheet shape is mainly used.

Examples of the material forming the structure of the filter element include metals (stainless steel, nickel steel, etc.), resins, and the like. Among these, metals (stainless steel, nickel steel, etc.) are preferable, and stainless steel is more preferable.

The filtration accuracy of the filter element is preferably 25 μm or less, more preferably 10 μm or less, from the viewpoint of removing foreign matters in the resin composition.

As the filter element, specifically, Naslon filter manufactured by Nippon Seisen Co., Ltd., Dena filter manufactured by Nagase & Co., Ltd., or the like can be used.

The polymer filter used in the present invention may be attached to the outlet side of the extruder, or may be attached to the outlet side of the gear pump interposed between the extruder and the polymer filter.

The pressure difference P1 between the resin pressure at the inlet and the resin pressure at the outlet of the polymer filter at the start of melt extrusion from the extruder is preferably P1≧8 MPa, and more preferably P1≧9 MPa. When P1<8 MPa, the back pressure applied to the polymer filter becomes small, and foreign matter in the polymer filter is less likely to be discharged, which is not preferable. Although the upper limit of the differential pressure P1 is not limited, it is preferable that P1<10 MPa, for example. This is because the polymer filter may be damaged when the pressure is 10 MPa or more.

Here, the start of melt extrusion from the extruder refers to the start of filtration of the molten resin by the polymer filter in a state where the polymer filter is filled with the molten resin.

The differential pressure P2 between the resin pressure at the inlet of the polymer filter and the resin pressure at the outlet of the polymer filter is preferably 1 MPa or more and less than 8 MPa, and more preferably 4 MPa or more and less than 8 MPa. If the pressure is less than 1 MPa, the flow of the molten resin becomes non-uniform, and local resin flow-prone portions are likely to occur in the polymer filter, and there is concern that resin deterioration and foreign matter may occur. However, it is not preferable because foreign substances captured by the polymer filter may be discharged during production.

Here, the pressure differences P1 and P2 between the resin pressure at the inlet and the resin pressure at the outlet of the polymer filter can be measured as follows. The value of the resin pressure sensor attached to the inlet and outlet of the polymer filter can be measured from the difference between them (resin pressure at the inlet of the polymer filter)-(resin pressure at the outlet of the polymer filter).

At the start of melt extrusion from the extruder, the amount W [kg] of the thermoplastic resin composition to be flown into the polymer filter is determined by arranging B sheets of circular sheet filters having a diameter of A inches as filter elements. When used, it is necessary to satisfy the relation of W≧A×B/10 [kg], and it is preferable to satisfy the relation of W≧A×B/5 [kg]. Thereby, the foreign matter in the polymer filter can be efficiently and sufficiently discharged in a short time.

Here, the diameter of the filter element refers to the length of the diameter of the outer circumference circle of the circular filter element.

It is preferable that the resin temperature T1 in the polymer filter at the differential pressure P1 [MPa] and the resin temperature T2 in the polymer filter at the differential pressure P2 [MPa] satisfy the relationship represented by T1≦T2. This is because the relationship of P1>P2 may not be satisfied when T1>T2.

The resin temperature in the polymer filter is preferably higher than 240°C and lower than 300°C. If the temperature is 240° C. or lower, the resin pressure increases, which may cause breakage of the polymer filter, and if the temperature is 300° C. or higher, thermal decomposition of the resin in the polymer filter may occur, which is not preferable. The resin temperature at the inlet of the polymer filter is preferably 230° C. or higher and 310° C. or lower in order not to affect the resin temperature in the polymer filter.

Here, the resin temperature inside the polymer filter and the resin temperature at the polymer filter inlet can be measured as follows. The temperature of the resin inside the polymer filter can be measured by measuring the temperature of the molten resin flowing out from the filter outlet, and the temperature of the resin at the polymer filter inlet can be measured by measuring the temperature of the molten resin flowing into the filter inlet with a contact thermometer.

The polymer filter used in the production method of the present invention may be an unused polymer filter or a reused polymer filter.

Here, the unused polymer filter means a polymer filter which has not yet been subjected to filtration of the thermoplastic resin composition. There is a possibility that foreign matter, such as foreign matter mixed in when the filter element is manufactured or when the filter element is assembled into a polymer filter, is attached to the unused polymer filter.

The reused polymer filter means a polymer filter obtained by filtering the thermoplastic resin composition at least once. When the polymer filter is reused, it may be reused as it is, but it is preferable to wash it at least once from the viewpoint of heat deterioration of the resin staying in the polymer filter for a long time and generation of foreign matter. The method for washing the polymer filter is not particularly limited, but for example, a roasting washing method and a solvent washing method can be used. The former roasting and cleaning method is to remove the resin adhering to the filter element by putting the filter element taken out from the polymer filter into, for example, a furnace and raising the atmospheric temperature in the furnace to the thermal decomposition temperature of the resin in the presence of oxygen. It is a method of cleaning by thermal decomposition. In the latter solvent washing method, for example, the filter element taken out from the polymer filter is immersed in a solvent such as ethylene glycol, N-methylpyrrolidinone, or N-methylpyrrolidone heated to near the boiling point to dilute the resin attached to the filter element. It is a method of washing by doing. In the roasting cleaning method, there is a possibility that carbonized resin may remain in the filter without being sufficiently thermally decomposed, and also in the solvent cleaning method, in particular, a rubber-like polymer, etc., in a portion where the molten resin is likely to stay. The crosslinkable resin may remain.

[Thermoplastic resin composition]
The thermoplastic resin composition containing the rubber-like polymer component obtained by the production method of the present invention will be described. The thermoplastic resin composition has a rubber-like polymer component and a thermoplastic resin.

The content of the rubber-like polymer in the thermoplastic resin composition is preferably 1 to 60% by weight, more preferably 5 to 50% by weight, further preferably 10 to 40% by weight. preferable. This is because it is preferable from the viewpoint that strength and toughness can be imparted to the film within a range that does not affect the moldability of the film made of the thermoplastic resin composition.

The thermoplastic resin composition is produced by melt-kneading the rubber-like polymer component and the thermoplastic resin and then cooling. The shape of the obtained thermoplastic resin composition is not particularly limited, and various shapes such as pellet shape and film shape can be mentioned. In the case of a film shape, after melt-kneading the rubber-like polymer and the thermoplastic resin, it may be cooled and molded into a film shape, after melt-kneading the rubber-like polymer and the thermoplastic resin, into a pellet shape Then, it may be melted again and cooled into a film shape to be molded.

(Rubber polymer)
The resin constituting the rubber-like polymer is not particularly limited, and examples thereof include rubber-like polymers such as a butadiene-based cross-linked polymer, a (meth)acrylic cross-linked polymer, and an organosiloxane-based cross-linked polymer. Among them, a (meth)acrylic crosslinked polymer (acrylic rubber-like polymer) is particularly preferable in terms of weather resistance (light resistance) and transparency of the film made of the thermoplastic resin composition obtained.

Examples of the (meth)acrylic crosslinked polymer include ABS resin rubber and ASA resin rubber. From the viewpoint of transparency and the like, an acrylic graft copolymer containing the acrylic ester rubbery polymer shown below. (Hereinafter, simply referred to as "acrylic graft copolymer") is preferable.

The acrylic graft copolymer can be obtained by polymerizing a monomer mixture containing methacrylic acid ester as a main component in the presence of an acrylic acid ester rubbery polymer.

The acrylic acid ester-based rubber-like polymer is a rubber-like polymer containing an acrylic acid ester as a main component, and specifically, 50% by weight or more and 100% by weight or less of acrylic acid ester and other copolymerizable vinyl-based polymers. Monomer mixture (100% by weight) consisting of 0% by weight to 50% by weight of monomer and 0.05 to 10 parts by weight of polyfunctional monomer (based on 100 parts by weight of monomer mixture). Those obtained by polymerizing) are preferable. The monomers may be mixed and used, or the monomer composition may be changed and used in two or more stages.

As the acrylate ester, it is preferable to use one having an alkyl group having 1 to 12 carbon atoms from the viewpoint of polymerizability and cost. For example, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, 2-butyl acrylate, isobutyl acrylate, benzyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, Examples thereof include phenoxyethyl acrylate and phenyl acrylate, and these monomers may be used in combination of two or more kinds. The amount of acrylic acid ester is preferably 50% by weight or more and 100% by weight or less, more preferably 60% by weight or more and 99% by weight or less, still more preferably 70% by weight or more and 99% by weight or less, based on 100% by weight of the monomer mixture. Most preferably, it is not less than 99% by weight. If it is less than 50% by weight, the impact resistance tends to be low, the elongation at tensile rupture tends to be low, and cracking tends to occur when the film is cut.

As the other copolymerizable vinyl-based monomer, methacrylic acid esters are particularly preferable from the viewpoint of weather resistance and transparency, and examples thereof include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, Examples thereof include 2-butyl methacrylate, isobutyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, phenoxyethyl methacrylate, phenyl methacrylate and the like. Aromatic vinyls and their derivatives, and vinyl cyanides are also preferable, and examples thereof include styrene, methylstyrene, acrylonitrile, methacrylonitrile and the like. Other examples include unsubstituted and/or substituted maleic anhydrides, (meth)acrylamides, vinyl esters, vinylidene halides, (meth)acrylic acid and its salts, (hydroxyalkyl)acrylic acid esters and the like.

The polyfunctional monomer may be one usually used, for example, allyl methacrylate, allyl acrylate, triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, diallyl malate, divinyl adipate, divinylbenzene, ethylene glycol dimethacrylate, Diethylene glycol methacrylate, triethylene glycol dimethacrylate, trimethylol propane trimethacrylate, tetromethylol methane tetramethacrylate, dipropylene glycol dimethacrylate and their acrylates can be used. Two or more kinds of these polyfunctional monomers may be used.

The amount of the polyfunctional monomer is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the total amount of the monomer mixture. If the amount of the polyfunctional monomer added is less than 0.05 parts by weight, a crosslinked product cannot be formed, and if it exceeds 10 parts by weight, the crack resistance of the film tends to decrease.

The acrylic graft copolymer is a monomer mixture 95 containing methacrylic acid ester as a main component in the presence of 5 to 90 parts by weight (more preferably 5 to 75 parts by weight) of an acrylic acid ester rubbery polymer. What is obtained by polymerizing -25 parts by weight in at least one stage is preferable. The methacrylic acid ester in the graft copolymer composition (monomer mixture) is preferably 50% by weight or more. If it is less than 50% by weight, the hardness and rigidity of the obtained film tend to decrease.

Polymerization of a monomer mixture containing a methacrylic acid ester as a main component into an acrylic acid ester-based rubbery polymer, that is, as a monomer used for graft copolymerization, the above-mentioned methacrylic acid ester, acrylic acid ester, these A vinyl-based monomer copolymerizable with methacrylic acid can be similarly used, and methacrylic acid ester and acrylic acid ester are preferably used. From the viewpoint of compatibility with acrylic resins, methyl methacrylate is preferable, and from the viewpoint of suppressing zipper depolymerization, methyl acrylate, ethyl acrylate, and n-butyl acrylate are preferable.

From the viewpoint of optical isotropy, a (meth)acrylic monomer having an alicyclic structure, a heterocyclic structure or an aromatic group (referred to as a “ring structure-containing (meth)acrylic monomer”). ) Is preferable, and specific examples thereof include benzyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and phenoxyethyl (meth)acrylate. The amount used is 1 to 100% by weight based on 100% by weight of the total amount of the monomer mixture (total amount of the ring structure-containing (meth)acrylic monomer and other monofunctional monomer copolymerizable therewith). Is preferred, 5 to 70 wt% is more preferred, and 5 to 50 wt% is most preferred. As the other monofunctional monomer copolymerizable therewith, the above-mentioned methacrylic acid ester, acrylic acid ester, and other copolymerizable vinyl-based monomer can be similarly used.

The graft ratio with respect to the acrylate rubber polymer is preferably 10 to 250%, more preferably 40 to 230%, and most preferably 60 to 220%. If the graft ratio is less than 10%, the resulting acrylic-based graft copolymer is likely to aggregate in the thermoplastic resin composition, which may reduce transparency or cause foreign matter. Further, the elongation at the time of tensile rupture is lowered, and cracks are likely to occur when the film made of the thermoplastic resin composition is cut. When it is 250% or more, the melt viscosity at the time of molding, for example, at the time of molding a film made of a thermoplastic resin composition becomes high, and the moldability of the film tends to be lowered. The calculation formula will be described in the section of Examples.

The graft ratio is the weight ratio of the graft component in the acrylic graft copolymer, and is measured by the following method. 2 g of the obtained acrylic graft copolymer was dissolved in 50 ml of methyl ethyl ketone and centrifuged for 1 hour at a rotation speed of 30,000 rpm and a temperature of 12° C. using a centrifuge (CP60E manufactured by Hitachi Koki Co., Ltd.) to obtain insoluble matter. And soluble fractions (centrifugation work is set three times in total). The obtained insoluble matter is calculated as an acrylic acid ester-based graft polymer by the following formula.

Graft ratio (%)=[{(weight of methyl ethyl ketone insoluble matter)-(weight of acrylic acid ester-based rubbery polymer)}/(weight of acrylic acid ester-based rubbery polymer)]×100

The acrylic rubber-like polymer is preferably blended so as to be contained in 1 to 60 parts by weight, more preferably 1 to 30 parts by weight, and further preferably 1 to 25 parts by weight in 100 parts by weight of the thermoplastic resin composition. preferable. If it is less than 1 part by weight, crack resistance and vacuum formability of the film may be deteriorated, and the photoelastic constant may be increased, resulting in poor optical isotropy. On the other hand, if the amount exceeds 60 parts by weight, the heat resistance, surface hardness, transparency and bending whitening resistance of the film tend to deteriorate.

Where the rubber-like polymer can be in the form of particles, the volume average particle diameter of the rubber-like polymer particles is preferably 20 to 450 nm, more preferably 20 to 300 nm, further preferably 20 to 150 nm, most preferably 30 to 80 nm. preferable. If it is less than 20 nm, crack resistance may deteriorate. On the other hand, if it exceeds 450 nm, the transparency may decrease. The volume average particle diameter can be measured by a dynamic scattering method, for example, by using MICROTRAC UPA150 (manufactured by Nikkiso Co., Ltd.).

The acrylic graft copolymer can be produced by a general emulsion polymerization method. Specifically, a method of continuously polymerizing an acrylic acid ester monomer using an emulsifier in the presence of a water-soluble polymerization initiator can be exemplified.

In the emulsion polymerization method, it is preferable to carry out continuous polymerization in a single reaction tank, and it is not preferable to use two or more reaction tanks because the mechanical stability of the latex decreases.

The polymerization temperature is preferably 30°C or higher and 100°C or lower, more preferably 50°C or higher and 80°C or lower. If the temperature is lower than 30°C, the productivity tends to decrease, and if the temperature exceeds 100°C, the target molecular weight tends to be excessively high, and the quality tends to deteriorate. Raw materials such as acrylic acid ester monomer, initiator, emulsifier and deionized water, which are continuously added to the polymerization reaction tank, are accurately added under the control of a metering pump, but the heat of polymerization generated in the reaction tank is used. In order to secure the amount of heat removed, it is possible to pre-cool as necessary. If necessary, a polymerization inhibitor, a coagulant, a flame retardant, an antioxidant and a pH adjuster may be added to the latex discharged from the reaction tank to collect unreacted monomers and post-polymerize them. You can go. Then, the copolymer can be obtained through known methods such as coagulation, heat treatment, dehydration, water washing, and drying.

In emulsion polymerization, a usual polymerization initiator can be used. For example, inorganic peroxides such as potassium persulfate and sodium persulfate, organic peroxides such as cumene hydroperoxide and benzoyl peroxide, and oil-soluble initiators such as azobisisobutyronitrile are also used. These may be used alone or in combination of two or more. These initiators are ordinary redox type polymerization initiators used in combination with sodium sulfite, sodium thiosulfate, sodium formaldehyde, sulfoxylate, ascorbic acid, ferrous sulfate and a reducing agent of ethylenediaminetetraacetic acid disodium complex. May be used.

A chain transfer agent may be used in combination with the polymerization initiator. Examples of the chain transfer agent include alkylmercaptans having 2 to 20 carbon atoms, mercapto acids, thiophenol, carbon tetrachloride and the like, and these may be used alone or in combination of two or more kinds.

There is no particular limitation on the emulsifier used in the emulsion polymerization method, and any emulsifier for ordinary emulsion polymerization can be used. For example, sulfate ester salt-based surfactants such as sodium alkylsulfate, sodium alkylbenzenesulfonate, sodium alkylsulfonate, sulfonate-based surfactants such as sodium dioctylsulfosuccinate, sodium alkylphosphate ester, polyoxyethylene alkyl ether Anionic surfactants such as phosphate-based surfactants such as sodium phosphate are included. The sodium salt may be other alkali metal salt such as potassium salt or ammonium salt. These emulsifiers may be used alone or in combination of two or more. Furthermore, nonionic surfactants represented by polyoxyalkylenes or their alkyl or aryl-substituted terminal hydroxyl groups may be used or partially used in combination. Among them, from the viewpoint of polymerization reaction stability and particle system controllability, a sulfonate-based surfactant or a phosphate-based surfactant is preferable, and among them, dioctyl sulfosuccinate or polyoxyethylene alkyl ether phosphate. An ester salt can be more preferably used.

The amount of the emulsifier to be used is preferably 0.05 parts by weight or more and 10 parts by weight, and more preferably 0.1 parts by weight or more and 1.0 part by weight or less, based on 100 parts by weight of the entire monomer component. If the amount is less than 0.05 parts by weight, the particle size of the copolymer tends to be too large, and if it is more than 10 parts by weight, the particle size of the copolymer tends to be too small, and the particle size distribution tends to deteriorate. ..

(Thermoplastic resin)
The thermoplastic resin contained in the thermoplastic resin composition containing the rubbery polymer component obtained by the production method of the present invention is not particularly limited, but specifically, a polycarbonate resin represented by bisphenol A polycarbonate; polystyrene. , Styrene-acrylonitrile copolymers, styrene-maleic anhydride resins, styrene-maleimide resins, styrene-(meth)acrylic acid resins, aromatic vinyl resins such as styrene-based thermoplastic elastomers and hydrogenated products thereof; amorphous Polyolefins, transparent polyolefins having a finer crystal phase, polyolefin resins such as ethylene-methyl methacrylate resin; acrylic resins such as polymethyl methacrylate and styrene-methyl methacrylate resin, and their imide cyclization and lactone cyclization. , Heat-resistant acrylic resins modified by methacrylic acid modification, etc.; amorphous polyester resins or crystals such as polyethylene terephthalate or polyethylene terephthalate, polyethylene naphthalate, polyarylate, etc. partially modified with cyclohexane dimethylene groups, isophthalic acid, etc. A transparent thermoplastic resin such as a transparent polyester resin having a finer phase; a polyimide resin; a polyether sulfone resin; a polyamide resin; a cellulosic resin such as a triacetyl cellulose resin; a polyphenylene oxide resin or the like is widely exemplified. In consideration of actual use, it is preferable to select the resin so that the total light transmittance of the obtained molded product is 85% or more, preferably 90%, more preferably 92% or more.

Among the above resins, acrylic resins are particularly preferable in terms of excellent optical properties, heat resistance, moldability and the like. The acrylic resin is not particularly limited, but a methacrylic resin containing methyl methacrylate as a monomer component can be used, and the methyl methacrylate is 30 to 100% by weight, preferably 50 to 99.9% by weight. The content is preferably 50 to 98% by weight, and the monomer copolymerizable with methyl methacrylate is 70 to 0% by weight, preferably 50 to 0.1% by weight, more preferably 50 to 2% by weight. When the content of methyl methacrylate is less than 30% by weight, the optical characteristics, appearance, weather resistance and heat resistance peculiar to the acrylic resin tend to be deteriorated. Further, from the viewpoint of processability and appearance, it is desirable not to use a polyfunctional monomer.

When a methacrylic resin containing methyl methacrylate as a monomer component is used, the glass transition temperature of the methacrylic resin can be set according to the conditions of use and the application. The glass transition temperature is preferably 100°C or higher, more preferably 110°C or higher, even more preferably 115°C or higher, and most preferably 120°C or higher.

Further, a heat-resistant acrylic resin can be used, for example, a resin in which an N-substituted maleimide compound is copolymerized as a copolymerization component, a glutaric anhydride resin, a resin having a lacto-BR> throwing structure, a glutarimide. A resin, a resin containing a hydroxyl group and/or a carboxyl group, an aromatic vinyl monomer and an aromatic vinyl-containing polymer obtained by polymerizing another monomer copolymerizable therewith, or a partial aromatic ring thereof. Hydrogenated aromatic vinyl-containing polymer obtained by hydrogenating all or all of them (for example, the aromatic ring of a styrene-based polymer obtained by polymerizing a styrene monomer and another monomer copolymerizable therewith) Partially hydrogenated styrene polymer obtained by partial hydrogenation), an acrylic polymer containing a cyclic acid anhydride repeating unit, and 97 to 100% by weight of methyl methacrylate and 3 to 0% by weight of methyl acrylate. Examples thereof include acrylic polymers.

In particular, a glutarimide resin can be more preferably used from the viewpoint of the heat resistance of the obtained thermoplastic resin composition or optical film, and from the optical characteristics during stretching.
The glutarimide resin will be described in detail below. Specific examples of the glutarimide resin include, for example, the following general formula (1)

(In the formula, R ¹ and R ² are each independently hydrogen or an alkyl group having 1 to 8 carbon atoms, R ³ is an alkyl group having 1 to 18 carbon atoms, or a cycloalkyl having 3 to 12 carbon atoms. Or a substituent containing an aromatic ring having 5 to 15 carbon atoms.)
And a unit represented by the following general formula (2)

(In the formula, R ⁴ and R ⁵ are each independently hydrogen or an alkyl group having 1 to 8 carbon atoms, and R ⁶ is an alkyl group having 1 to 18 carbon atoms, a cycloalkyl having 3 to 12 carbon atoms. A glutarimide resin containing a unit (hereinafter, also referred to as “(meth)acrylic acid ester unit”) represented by a group or a substituent containing an aromatic ring having 5 to 15 carbon atoms is preferably used. You can

Further, the glutarimide resin is, if necessary, the following general formula (3)

(In the formula, R ⁷ is hydrogen or an alkyl group having 1 to 8 carbon atoms, and R ⁸ is an aryl group having 6 to 10 carbon atoms.) (hereinafter, “aromatic vinyl unit”) Also referred to as “”).

In the general formula (1), R ¹ and R ² are each independently hydrogen or a methyl group, R ³ is preferably hydrogen, a methyl group, a butyl group, or a cyclohexyl group, and R ¹ is More preferably, it is a methyl group, R ² is hydrogen, and R ³ is a methyl group.

The glutarimide resin may include only a single type as a glutarimide unit, or may include a plurality of types in which R ¹ , R ² and R ³ in the general formula (1) are different. Good.

The glutarimide unit can be formed by imidizing the (meth)acrylic acid ester unit represented by the general formula (2).

Further, an acid anhydride such as maleic anhydride, or a half ester of such an acid anhydride and a linear or branched alcohol having 1 to 20 carbon atoms; acrylic acid, methacrylic acid, maleic acid, maleic anhydride, The glutarimide unit can also be formed by imidizing an α,β-ethylenically unsaturated carboxylic acid such as itaconic acid, itaconic anhydride, crotonic acid, fumaric acid, and citraconic acid.

In the general formula (2), R ⁴ and R ⁵ are each independently hydrogen or a methyl group, R ⁶ is preferably hydrogen or a methyl group, R ⁴ is hydrogen, and R ⁵ is More preferably, it is a methyl group and R ⁶ is a methyl group.

The glutarimide resin may include only a single type as the (meth)acrylic acid ester unit, or may include a plurality of types having different R ⁴ , R ⁵ , and R ⁶ in the general formula (2). May be included.

The glutarimide resin preferably contains styrene, α-methylstyrene or the like as the aromatic vinyl constituent unit represented by the general formula (3), and more preferably contains styrene.

Further, the glutarimide resin may include only a single type or a plurality of types having different R ⁷ and R ⁸ as the aromatic vinyl constituent unit.

In the glutarimide resin, the content of the glutarimide unit represented by the general formula (1) is not particularly limited, and it is preferably changed depending on the structure of R ³ , for example.

Generally, the content of the glutarimide unit is preferably 1% by weight or more of the glutarimide resin, more preferably 1% by weight to 95% by weight, and 2% by weight to 90% by weight. Is more preferable, and it is particularly preferable that the amount is 3 to 80% by weight.

If the content of the glutarimide unit is within the above range, the heat resistance and transparency of the obtained glutarimide resin may be reduced, or the moldability and the mechanical strength when processed into a film may be reduced. There is no.

On the other hand, if the content of the glutarimide unit is less than the above range, the heat resistance of the obtained glutarimide resin tends to be insufficient, or the transparency tends to be impaired. Further, if it is more than the above range, heat resistance and melt viscosity unnecessarily increase, molding processability deteriorates, mechanical strength during film processing becomes extremely brittle, and transparency is impaired. Tend.

In the glutarimide resin, the content of the aromatic vinyl unit represented by the general formula (3) is not particularly limited and can be appropriately set according to the required physical properties. The content of the aromatic vinyl unit represented by the general formula (3) may be 0 depending on the intended use. When the aromatic vinyl unit represented by the general formula (3) is contained, it is preferably 10% by weight or more, and more preferably 10% by weight to 40% by weight, based on the total repeating units of the glutarimide resin. More preferably, it is more preferably 15% by weight to 30% by weight, and particularly preferably 15% by weight to 25% by weight.

When the content of the aromatic vinyl unit is within the above range, the heat resistance of the obtained glutarimide resin will not be insufficient and the mechanical strength during film processing will not be reduced.

On the other hand, when the content of the aromatic vinyl unit is more than the above range, the heat resistance of the obtained glutarimide resin tends to be insufficient.

If necessary, the glutarimide resin may further be copolymerized with other units other than the glutarimide unit, the (meth)acrylic acid ester unit, and the aromatic vinyl unit.

As other units, for example, a nitrile-based monomer such as acrylonitrile or methacrylonitrile, a maleimide-based monomer such as maleimide, N-methylmaleimide, N-phenylmaleimide, or N-cyclohexylmaleimide is copolymerized. Structural units can be mentioned.

These other units may be directly copolymerized or graft copolymerized in the glutarimide resin.

The weight average molecular weight of the glutarimide resin is not particularly limited, but it is preferably 1×10 ^{4 to} 5×10 ⁵ . Within the above range, the molding processability does not decrease and the mechanical strength during film processing does not become insufficient.

On the other hand, when the weight average molecular weight is smaller than the above range, the mechanical strength of the film tends to be insufficient. On the other hand, when it is larger than the above range, the viscosity at the time of melt extrusion is high, the moldability tends to deteriorate, and the productivity of the molded product tends to decrease.

The glass transition temperature of the glutarimide resin is not particularly limited, but is preferably 110°C or higher, more preferably 120°C or higher. When the glass transition temperature is within the above range, the applicable range of the obtained thermoplastic resin composition can be expanded.

The method for producing the glutarimide resin is not particularly limited, and examples thereof include the method described in JP 2008-273140 A.

The thermoplastic resin composition containing the rubber-like polymer component obtained by the production method of the present invention, an antioxidant for improving the stability against heat or light, an ultraviolet absorber, an ultraviolet stabilizer or the like alone or You may add together 2 or more types.

[Method for producing optical film]
The method for producing an optical film comprising the thermoplastic resin composition of the present invention is a method for producing an optical film comprising a thermoplastic resin composition containing a rubbery polymer component, wherein the thermoplastic resin composition is an extruder. Through the polymer filter, and the thermoplastic resin composition is molded after the filtration, the filtration of the polymer filter at the start of melt extrusion from the extruder. At the pressure difference P1 [MPa] between the resin pressure at the inlet and the resin pressure at the outlet, W (kg) of the amount of the thermoplastic resin composition represented by the following formula (1) is flowed into the polymer filter, and then the polymer filter is used. The pressure difference between the resin pressure at the inlet and the resin pressure at the outlet is set to P2 [MPa] and the thermoplastic resin composition is caused to flow into the polymer filter, and the pressure differences P1 and P2 are expressed by the following formula (2). ) Is satisfied.
W≧A×B/10 [kg] (1)
A: Diameter of filter element (inch), B: Number of filter elements P1≧8 MPa, and P1>P2 (2)

In the method for producing an optical film made of the thermoplastic resin composition of the present invention, the melt extrusion method can be preferably used because of its productivity and work environment.

Examples of the film molding method by the melt extrusion method include T-die extrusion molding, calender molding, roll molding, and inflation molding. However, the film forming method is not limited to these. Further, thermoforming by heating, vacuum forming, and press forming are possible.

According to the method for producing an optical film made of the thermoplastic resin composition of the present invention, it is possible to suppress remarkable foreign matter generated in the optical film within a short period of time from the start of use of an unused or reused polymer filter.

The thickness of the optical film obtained by the production method of the present invention is suitably 20 μm or more and 500 μm or less, and more preferably 40 μm or more and 200 μm or less. When it is less than 20 μm, the toughness of the film tends to decrease, which is not preferable, while when it exceeds 500 μm, the transparency of the film tends to decrease, which is not preferable.

Since the optical film obtained by the production method of the present invention can reduce the number of foreign matters having an outer dimension of 30 μm or more in the longitudinal direction per 300 mm×300 mm square to 10 or less in a short time from the start of production, it is extremely small. Also, the unevenness of the film surface can be reduced, and the deterioration of the quality of the optical film surface can be further prevented.

The optical film obtained by the production method of the present invention is a member used for a display device such as a liquid crystal display device, for example, a polarizer protective film, a retardation film, a brightness enhancement film, a liquid crystal substrate, a light diffusion sheet, a prism sheet, or the like. Can be used. Above all, it is suitable for a polarizing plate protective film and a retardation film.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto. In the following description, "part" represents "part by weight" unless otherwise specified. The optical films in Examples and Comparative Examples were evaluated by the following methods.

(The pressure difference between the resin pressure at the inlet of the polymer filter and the resin pressure at the outlet)
The resin pressure at the inlet of the polymer filter and the resin pressure at the outlet are measured by the resin pressure sensors installed at the inlet and the outlet of the polymer filter respectively, and the difference between them (resin pressure at the polymer filter inlet)-(resin pressure at the polymer filter outlet) ) Was calculated as the differential pressure between the resin pressure at the inlet of the polymer filter and the resin pressure at the outlet.

(Resin temperature in polymer filter)
The resin temperature in the polymer filter was determined by measuring the temperature of the molten resin flowing out from the filter outlet with a contact thermometer.

(Evaluation of foreign matter in film)
A 300 mm×300 mm square test piece was cut out, and the foreign matter extracted by visual evaluation from the film was evaluated for the number of foreign matter having a size of 30 μ or more using a digital microscope (VHX1000 manufactured by Keyence Corporation).

The substances represented by the abbreviations in Production Examples and Examples are shown below.
BA: Butyl acrylate MMA: Methyl methacrylate CHP: Cumene hydroperoxide tDM: Tertiary decyl mercaptan AIMA: Allyl methacrylate

(Production Example 1: Preparation of rubbery polymer component)
Deionized water 200 parts Polyoxyethylene lauryl ether sodium phosphate 0.05 parts Sodium formaldehyde sulfoxylate 0.11 parts Ethylenediaminetetraacetic acid-2-sodium 0.004 parts Ferrous sulfate 0.001 parts

After the inside of the polymerization machine was sufficiently replaced with nitrogen gas to make it substantially oxygen-free, the internal temperature was adjusted to 40° C., and the mixture (A) (45 parts by weight of a monomer mixture consisting of 90% by weight of BA and 10% by weight of MMA) was used. 45.491 parts of a mixture obtained by adding 0.45 part of AIMA and 0.041 part of CHP) were continuously added over 225 minutes. 20 minutes, 40 minutes, and 60 minutes after the start of addition of the mixture (A), sodium polyoxyethylene lauryl ether phosphate (polyoxyethylene lauryl ether phosphate (manufactured by Toho Chemical Industry Co., Ltd., trade name: phosphanol RD- Sodium salt of 510Y) 0.2 part each was added to the polymerization machine, and after the addition was completed, the polymerization was continued for another 0.5 hour to obtain an acrylic ester rubber-like polymer (polymer of mixture (A)). The polymerization conversion rate was 98.6%.

Then, the internal temperature was adjusted to 60° C., 0.2 parts of sodium formaldehyde sulfoxylate was charged, and then the mixture (B) (57.8 wt% MMA, 4 wt% BA, and 38.2 wt% benzyl methacrylate) was added. 55.554 parts of a mixture obtained by adding 0.3 part of tDM and 0.254 part of CHP to 55 parts of the monomer mixture) are continuously added over 210 minutes, and the polymerization is further continued for 1 hour. A copolymer latex was obtained. The polymerization conversion rate was 100.0%. The obtained latex was salted out with magnesium sulfate, coagulated, washed with water and dried to obtain a white powdery acrylic graft copolymer.

The average particle diameter of the acrylate rubber polymer (polymer of the mixture (A)) was 121 nm. The graft ratio of the acrylic graft copolymer was 56%.

(Production Example 2: Preparation of thermoplastic resin)
A glutarimide resin (A1) was produced using polymethylmethacrylate as a raw material resin and monomethylamine as an imidizing agent.

In this production, a tandem type reactive extruder in which two extrusion reactors were arranged in series was used.

Regarding the tandem type reactive extruder, the first extruder and the second extruder both have a diameter of 75 mm and an L/D (ratio of the length L of the extruder to the diameter D) of 74 is a mesh type twin-screw extruder of the same direction. Was used to supply the raw material resin to the raw material supply port of the first extruder using a constant weight feeder (manufactured by Kubota Corp.).

The pressure reduction degree of each vent in the first extruder and the second extruder was set to -0.095 MPa. Further, the internal pressure control mechanism for connecting the first extruder and the second extruder with a pipe having a diameter of 38 mm and a length of 2 m, and connecting the resin discharge port of the first extruder and the raw material supply port of the second extruder. Used a constant flow pressure valve.

The resin (strand) discharged from the second extruder was cooled with a cooling conveyor and then cut with a pelletizer to obtain pellets. Here, in order to determine the internal pressure of the component connecting the resin discharge port of the first extruder and the raw material supply port of the second extruder, or to determine the extrusion fluctuation, the discharge port of the first extruder, the first extruder and the first extruder A resin pressure gauge was provided at the central portion of the connecting part between the two extruders and at the discharge port of the second extruder.

In the first extruder, a polymethyl methacrylate resin (Mw: 105,000) was used as a raw material resin, and monomethylamine was used as an imidizing agent to produce an imide resin intermediate 1. At this time, the temperature of the highest temperature part of the extruder was 280° C., the screw rotation speed was 55 rpm, the raw material resin supply amount was 150 kg/hour, and the addition amount of monomethylamine was 2.0 parts per 100 parts of the raw material resin. The constant flow pressure valve was installed immediately before the raw material supply port of the second extruder, and the monomethylamine press-fitting portion pressure of the first extruder was adjusted to 8 MPa.

In the second extruder, after the residual imidizing agent and the by-product were removed by the rear vent and the vacuum vent, dimethyl carbonate was added as an esterifying agent to produce an imide resin intermediate 2. At this time, the barrel temperature of the extruder was 260° C., the screw rotation speed was 55 rpm, and the amount of dimethyl carbonate added was 3.2 parts with respect to 100 parts of the raw material resin. Further, after removing the esterifying agent with a vent, the product was extruded from a strand die, cooled in a water tank, and then pelletized with a pelletizer to obtain a glutarimide resin (A1).

The obtained glutarimide resin (A1) is an acrylic resin in which a glutamylimide unit represented by the general formula (1) and a (meth)acrylic acid ester unit represented by the general formula (2) are copolymerized. ..

(Production Example 3: Preparation of thermoplastic resin composition)
The acrylic graft copolymer obtained in (Production Example 1) and the glutarimide resin obtained in (Production Example 2) were blended at a weight ratio of 40:60. Then, the mixture of the acrylic graft copolymer and the glutarimide resin was melt-extruded with a φ40 mm vent type extruder (single screw extruder) with the cylinder temperature set at 260° C., and the mixture was provided at the extruder outlet. The resin that emerged as a strand from the die was cooled in a water tank, and a pelletized thermoplastic resin composition was obtained.

(Example 1)
The optical film manufacturing equipment is a leaf disk filter consisting of a φ40 mm bent single-screw extruder and a metal sintered fiber filter medium with a diameter of 4 inches and a filtration accuracy of 5 μm that has not been produced as a filter element in order from the upstream side. 20 lines of Seishin Co., Ltd., a gear pump, and a T die are arranged.

The above device was used. The resin temperature T1 in the polymer filter was set to 264° C., the pressure difference P1 between the resin pressure at the inlet and the resin pressure at the outlet of the polymer filter at the start of melt extrusion was set to 8.5 MPa, and the pelletization obtained in (Production Example 3) was performed. After injecting 15 kg of the thermoplastic resin composition (W), the resin temperature T2 in the polymer filter was 268° C., the pressure difference P2 between the resin pressure at the inlet and the resin pressure at the outlet of the polymer filter was 7.8 MPa, 25 kg of the pelletized thermoplastic resin composition resin (W') obtained in (Production Example 3) was introduced. An optical film was produced using a cast roll obtained by heating the molten sheet-shaped thermoplastic resin composition discharged from the T-die to 90°C. Then, when 40 kg of the pelletized thermoplastic resin composition obtained in (Production Example 3) was introduced from the start of melt extrusion, that is, 2 hours after the start of melt extrusion, the evaluation of foreign matter in the obtained film was performed. I went. The results are shown in Table 1.

(Example 2)
The optical film manufacturing apparatus is a leaf disk filter (φ40 mm bent type single-screw extruder in order from the upstream side) and a metal sintered fiber filter medium with a diameter of 8 inches and a filtration accuracy of 5 μm that has not been produced as a filter element. 80 pieces of Seisen Co., Ltd. Naslon), a gear pump, and a T die are arranged.

The above device was used. The resin temperature T1 in the polymer filter was set to 264° C., the pressure difference P1 between the resin pressure at the inlet and the resin pressure at the outlet of the polymer filter at the start of melt extrusion was set to 8.5 MPa, and the pelletization obtained in (Production Example 3) was performed. After injecting 120 kg of the thermoplastic resin composition (W), the resin temperature T2 in the polymer filter was 268° C., the pressure difference P2 between the resin pressure at the inlet and the resin pressure at the outlet of the polymer filter was 7.8 MPa, 180 kg of the pelletized thermoplastic resin composition (W′) obtained in (Production Example 3) was introduced. An optical film was produced using a cast roll obtained by heating the molten sheet-shaped thermoplastic resin composition discharged from the T-die to 90°C. Then, when 300 kg of the pelletized thermoplastic resin composition obtained in (Production Example 3) was introduced from the start of melt extrusion, that is, 2 hours after the start of melt extrusion, the evaluation of foreign matter in the obtained film was performed. I went. The results are shown in Table 1.

(Example 3)
The number of leaf disk filters was set to 15, 10 kg of the pelletized thermoplastic resin composition (W) obtained in (Production Example 3) was introduced, and the pelletized thermoplastic resin obtained in (Production Example 3) was introduced. When 20 kg of the composition (W′) was introduced and 30 kg of the pelletized thermoplastic resin composition obtained in (Production Example 3) was introduced from the start of melt extrusion, that is, 2 hours after the start of melt extrusion The evaluation of foreign matter in the film obtained by the same method as in (Example 1) except that the evaluation was performed in (1) was performed. The results are shown in Table 1.

(Example 4)
The diameter of the leaf disk filter was set to 5 inches, 35 kg of the pelletized thermoplastic resin composition (W′) obtained in (Production Example 3) was introduced, and the mixture was obtained in (Production Example 3) from the start of melt extrusion. Foreign matter in the film obtained in the same manner as in (Example 1) except that the evaluation was performed at the time when 50 kg of the pelletized thermoplastic resin composition was introduced, that is, at the time when 2 hours had elapsed from the start of melt extrusion. An evaluation was made. The results are shown in Table 1.

(Comparative Example 1)
The resin temperature T1 in the polymer filter is 275° C., the pressure difference P1 between the resin pressure at the polymer filter inlet and the resin pressure at the outlet is 6.5 MPa, and then the resin temperature T2 in the polymer filter is 279° C. and the pressure difference P2. In the film obtained in the same manner as in (Example 1), except that the pelletized thermoplastic resin composition (W') obtained in (Production Example 3) was flown in at 25 kg. Foreign matter was evaluated. The results are shown in Table 1.

(Comparative example 2)
The resin temperature T1 in the polymer filter was 264° C., the pressure difference P1 between the resin pressure at the polymer filter inlet and the resin pressure at the outlet was 8.5 MPa, and the pelletized thermoplastic resin composition obtained in (Production Example 3) 4 W of (W) was flown in, then the resin temperature T2 in the polymer filter was set to 268° C., the pressure difference P2 between the resin pressure at the inlet and the resin pressure at the outlet of the polymer filter was set to 7.8 MPa, and (Production Example 3) The foreign matter in the film obtained in the same manner as in (Example 1) was evaluated except that 36 kg of the obtained pelletized thermoplastic resin composition (W') was introduced. The results are shown in Table 1.

(Comparative example 3)
The resin temperature T1 in the polymer filter is 275° C., the pressure difference P1 between the resin pressure at the polymer filter inlet and the resin pressure at the outlet is 6.5 MPa, and the resin temperature T2 in the polymer filter is 279° C. The foreign matter in the film obtained in the same manner as in (Example 2) was evaluated except that the pressure difference P2 between the pressure and the resin pressure at the outlet was set to 5.8 MPa. The results are shown in Table 1.

(Comparative example 4)
The amount (W) of the pelletized thermoplastic resin composition obtained in (Production Example 3) was set to 30 kg, and 270 kg of the pelletized thermoplastic resin composition (W′) obtained in (Production Example 3) was introduced. Other than the above, foreign matter in the film obtained by the same method as in (Example 2) was evaluated. The results are shown in Table 1.

From the results of Table 1, as shown in Examples 1 to 4, according to the production method of the present invention, reduction of foreign matter in the optical film obtained in a short time from the start of use of the polymer filter can be confirmed. On the other hand, as shown in Comparative Examples 1 to 4, as a condition deviating from the manufacturing method of the present invention, a condition that the differential pressure P1 between the resin pressure at the inlet of the polymer filter and the resin pressure at the outlet is small, or the amount of the resin flowing into the polymer filter is small. When the film production is carried out under the condition that W is small, the generation of foreign matter is still confirmed within a short time from the start of using the polymer filter. Therefore, in the optical film obtained by the production method of the present invention, it becomes possible to suppress the generation of foreign matter in a short time from the start of use of the polymer filter, improving the quality of the optical film product and improving the production yield. Is possible.

10 Extruder 11 Gear Pump 12 Polymer Filter 13 Die 14 Die Exit 15 Thermoplastic Resin Composition 16 Elastic Roll 17 Cast Roll 18 Stretching Machine 19 Winder 21 Filter Element 22 Inlet 23 Outlet 24 Filter Support

Claims (5)

A method for producing a thermoplastic resin composition containing a rubbery polymer component,
The thermoplastic resin composition has a step of passing through an extruder and being filtered by a polymer filter,
In the filtration, the thermoplastic resin composition represented by the following formula (1) at a pressure difference P1 [MPa] between the resin pressure at the inlet and the resin pressure at the outlet of the polymer filter at the start of melt extrusion from the extruder. Flow amount W [kg] into the polymer filter, the thermoplastic resin composition is applied to the polymer filter by setting the pressure difference between the resin pressure at the inlet and the resin pressure at the outlet of the polymer filter to P2 [MPa]. Has a step of flowing in,
The differential pressures P1 and P2 satisfy the relationship represented by the following formula (2),
A method for producing a thermoplastic resin composition.
W≧A×B/10 [kg] (1)
A: Diameter of filter element (inch), B: Number of filter elements P1≧8 MPa, and P2<8 MPa (2) The resin temperature T1 in the polymer filter at the differential pressure P1 [MPa] and the resin temperature T2 in the polymer filter at the differential pressure P2 [MPa] satisfy the relationship represented by T1≦T2. A method for producing a thermoplastic resin composition. The method for producing a thermoplastic resin composition according to claim 1, wherein the thermoplastic resin forming the thermoplastic resin composition is an acrylic resin. A method for producing an optical film comprising a thermoplastic resin composition containing a rubbery polymer component,
The thermoplastic resin composition passes through an extruder, and has a step of being filtered by a polymer filter, and a step of molding the thermoplastic resin composition after the filtration,
In the filtration, the amount of the thermoplastic resin composition represented by the following formula (1) is defined by the differential pressure P1 [MPa] between the resin pressure at the inlet and the resin pressure at the outlet of the polymer filter at the start of melt extrusion from the extruder. Of W [kg] is flown into the polymer filter, and then the thermoplastic resin composition is flown into the polymer filter while setting the pressure difference between the resin pressure at the inlet and the resin pressure at the outlet of the polymer filter to P2 [MPa]. Has a step of
The differential pressures P1 and P2 satisfy the relationship represented by the following formula (2),
A method for producing an optical film comprising a thermoplastic resin composition.
W≧A×B/10 [kg] (1)
A: Diameter of filter element (inch), B: Number of filter elements P1≧8 MPa, and P2<8 MPa (2) The method for producing an optical film made of the thermoplastic resin composition according to claim 4, wherein the thermoplastic resin constituting the thermoplastic resin composition is an acrylic resin.