Method of manufacturing acrylic resin film, and apparatus of manufacturing acrylic resin film

Abstract

To provide a manufacturing method and a manufacturing apparatus of an acrylic resin film capable of holding uniformity of quality such as a thickness of the acrylic resin film.SOLUTION: Provided is a manufacturing method of an acrylic resin film including: an extruding step of feeding a raw material of the acrylic resin film from a raw material feeder 2 to an extruder 3, melting and kneading the fed raw material, and extruding a molten material obtained by melting and kneading; and a pressure boosting step of pressure-boosting the molten material extruded from the extruder 3 using gear pumps 4 and 6 connected on the downstream side of the extruder. The extruder 3 has a screw and a motor for rotating and driving the screw. In the extruding step, when a rotation speed of the screw is N, and a feeding quantity of the raw material to the extruder is Q, N is controlled so that a pressure of the molten material between the extruder and the gear pumps becomes constant, and an influence of the control of Q with respect to a pressure of the discharge side of the extruder is decreased by not controlling the Q or more mildly controlling the Q than the control of N. Also provided is a manufacturing apparatus of the acrylic resin film.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method and an apparatus for producing an acrylic resin film. [Background technology]

[0002] Conventionally, an acrylic resin film manufacturing apparatus is described in JP-A-2-6118. This manufacturing apparatus includes a raw material supplying machine, an extruder to which raw material is supplied from the raw material supplying machine, a gear pump connected to the downstream side of the extruder, a die connected to the downstream side of the gear pump, and a control device for controlling the raw material supplying machine and the extruder. The extruder includes a screw and a motor for rotating the screw, and kneads and melts the raw material, and extrudes it as a melt. The control device measures the pressure of the melt between the discharge side of the extruder and the suction side of the gear pump, and controls the amount of raw material supplied to the extruder (Q) and the number of rotations of the screw (N) so that this pressure is constant, thereby controlling the amount of melt extruded from the extruder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2-6118 Summary of the Invention [Problem to be solved by the invention]

[0004] However, even if Q and N are controlled, the amount of the melt extruded from the extruder is not stable, and when an acrylic resin film is produced from the melt through a die, the quality of the acrylic resin film, such as its thickness, may become non-uniform.

[0005] Therefore, an object of the present disclosure is to provide a method and apparatus for producing an acrylic resin film that can maintain uniformity in the quality of the acrylic resin film. [Means for solving the problem]

[0006] In order to solve the above problems, a method for producing an acrylic resin film according to one embodiment of the present disclosure includes the steps of: A supplying step of supplying a raw material for the acrylic resin film from a raw material supplying machine to an extruder; an extrusion step of melting and kneading the raw materials supplied from the raw material supplying device in the extruder, and extruding a molten material obtained by the melting and kneading to a downstream side of the extruder; a pressure increasing step of increasing the pressure of the molten material extruded from the extruder by a gear pump connected to the downstream side of the extruder; Equipped with The extruder includes a screw and a motor that rotates the screw. In the extrusion step, When the rotation speed of the screw is N and the amount of the raw material fed to the extruder is Q, N is controlled so that the pressure of the melt between the extruder and the gear pump is constant, and the following (i), (ii), and (iii) are performed. (i) No control over Q (ii) When the fluctuation range of Q / N from the reference value exceeds a set value, Q is controlled so that the fluctuation range of Q / N is equal to or less than the set value, whereas when the fluctuation range of Q / N is equal to or less than the set value, Q is not controlled. (iii) Controlling Q by reducing the effectiveness of the control of Q so that the pressure of the melt between the extruder and the gear pump is constant. Execute one of the following:

[0007] As a result of extensive research, the inventors of the present application have found that, in controlling Q and N, controlling N speeds up the response of the pressure on the discharge side of the extruder, while controlling Q slows down the response of the pressure on the discharge side of the extruder. As described above, because the response of Q control is slow, it is difficult to stably control the pressure on the discharge side of the extruder to be constant, and as a result, when an acrylic resin film is produced from a melt using a die, the quality of the acrylic resin film, such as its thickness, may become non-uniform. According to the above embodiment, N is controlled so that the pressure of the melt between the extruder and the gear pump is constant, and Q is not controlled or is controlled more loosely than N, thereby reducing the effect of controlling Q on the pressure on the discharge side of the extruder. This makes it easy to stably control the pressure on the discharge side of the extruder to a constant value, and makes it possible to maintain uniformity in quality, such as the thickness, of the acrylic resin film when it is produced from the melt downstream of the gear pump.

[0008] Preferably, in one embodiment of the method for producing an acrylic resin film, in the step (ii), Q is further controlled by reducing the effectiveness of control of Q.

[0009] According to the embodiment, the control of Q can be loosened, so that the pressure on the discharge side of the extruder can be controlled more stably.

[0010] Preferably, in one embodiment of the method for producing an acrylic resin film, in (iii) above, Q is further controlled so that when the fluctuation range of Q / N from a reference value exceeds a set value, the fluctuation range of Q / N becomes equal to or less than the set value.

[0011] According to the embodiment, the control of Q can be loosened, so that the pressure on the discharge side of the extruder can be controlled more stably.

[0012] Preferably, in one embodiment of the method for producing an acrylic resin film, the extruder is a twin-screw extruder.

[0013] According to the above embodiment, the twin-screw extruder is more susceptible to pressure fluctuations than the single-screw extruder, but the pressure fluctuations on the discharge side of the twin-screw extruder can be effectively reduced.

[0014] Preferably, in one embodiment of the method for producing an acrylic resin film, the raw material contains a plurality of types of materials having different shapes.

[0015] According to the embodiment, even if a plurality of types of materials having different shapes are fed into the extruder, pressure fluctuations on the discharge side of the extruder can be effectively reduced.

[0016] In addition, the acrylic resin film manufacturing apparatus according to one embodiment of the present disclosure includes: a feedstock supplying machine including a feedstock for an acrylic resin film; an extruder having a screw and a motor for rotating the screw, the extruder melting and kneading the raw material supplied from the raw material supplying device and extruding the raw material as a molten material; a gear pump connected downstream of the extruder to pressurize and discharge the molten material extruded from the extruder; When the rotation speed of the screw is N and the amount of the raw material fed to the extruder is Q, N is controlled so that the pressure of the melt between the extruder and the gear pump is constant, and the following (i), (ii), and (iii) are performed. (i) No control over Q (ii) When the fluctuation range of Q / N from the reference value exceeds a set value, Q is controlled so that the fluctuation range of Q / N is equal to or less than the set value, whereas when the fluctuation range of Q / N is equal to or less than the set value, Q is not controlled. (iii) Controlling Q by reducing the effectiveness of the control of Q so that the pressure of the melt between the extruder and the gear pump is constant. A control device that executes any one of the above. Equipped with.

[0017] According to the above embodiment, N is controlled so that the pressure of the melt between the extruder and the gear pump (hereinafter also referred to as the pressure on the discharge side of the extruder) is constant, and Q is not controlled or is controlled more loosely than N, thereby reducing the effect of controlling Q on the pressure on the discharge side of the extruder. This makes it easy to stably control the pressure on the discharge side of the extruder constant, and when an acrylic resin film is produced from the melt downstream of the gear pump, uniformity in quality such as the thickness of the acrylic resin film can be maintained.

[0018] Preferably, in one embodiment of the acrylic resin film manufacturing apparatus, in the step (ii), Q is controlled by reducing the effectiveness of control of Q.

[0019] According to the embodiment, the control of Q can be loosened while maintaining the fluctuation range of Q / N at or below the set value, so that the pressure on the discharge side of the extruder can be controlled more stably.

[0020] Preferably, in one embodiment of the acrylic resin film manufacturing apparatus, in (iii) above, Q is further controlled so that when the fluctuation range of Q / N from the reference value exceeds a set value, the fluctuation range of Q / N becomes equal to or less than the set value.

[0021] According to the embodiment, the control of Q can be loosened while maintaining the fluctuation range of Q / N at or below the set value, so that the pressure on the discharge side of the extruder can be controlled more stably.

[0022] Preferably, in one embodiment of the acrylic resin film manufacturing apparatus, the extruder is a twin-screw extruder.

[0023] According to the above embodiment, the twin-screw extruder is more susceptible to pressure fluctuations than the single-screw extruder, but the pressure fluctuations on the discharge side of the twin-screw extruder can be effectively reduced. Effect of the Invention

[0024] According to the acrylic resin film manufacturing method and acrylic resin film manufacturing apparatus which are one aspect of the present disclosure, uniformity in the quality of the acrylic resin film can be maintained. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a schematic diagram showing one embodiment of an acrylic resin film production apparatus. [Diagram 2] FIG. 2 is a schematic diagram showing a raw material supplying machine of the acrylic resin film manufacturing apparatus. [Diagram 3] FIG. 2 is a schematic diagram showing each member of the acrylic resin film manufacturing apparatus excluding a raw material supplying device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, an acrylic resin film manufacturing method and an acrylic resin film manufacturing apparatus according to one embodiment of the present disclosure will be described in detail with reference to the illustrated embodiments. Note that the drawings include some schematic views and may not reflect actual dimensions or ratios.

[0027] (Embodiment) <Summary configuration> Fig. 1 is a schematic diagram showing one embodiment of an acrylic resin film production apparatus. As shown in Fig. 1, the acrylic resin film production apparatus 1 includes a raw material supplying machine 2, an extruder 3, a first gear pump 4, a coarse filter 5, a second gear pump 6, a fine filter 7, a die 8, and a control device 9.

[0028] The acrylic resin film manufacturing apparatus 1 melts and kneads the raw materials for the acrylic resin film, and forms the acrylic resin film from the melt. In Fig. 1, the flow direction of the melt is indicated by an arrow. The raw material feeder 2, extruder 3, first gear pump 4, coarse filter 5, second gear pump 6, high-definition filter 7, and die 8 are arranged in this order from upstream to downstream of the flow of the melt.

[0029] The raw material supplying machine 2 contains raw materials for the acrylic resin film. The extruder 3 kneads and melts the raw materials supplied from the raw material supplying machine 2, and extrudes the molten material obtained by this melt kneading to the downstream side of the extruder 3. The extruder 3 has a screw and a motor that rotates and drives the screw.

[0030] The first gear pump 4 is connected downstream of the extruder 3, and increases the pressure of the molten material extruded from the extruder 3 and discharges it. The second gear pump 6 is connected downstream of the first gear pump 4, and increases the pressure of the molten material discharged from the first gear pump 4 and discharges it.

[0031] The coarse filter 5 is connected between the first gear pump 4 and the second gear pump 6, and filters the melt discharged from the first gear pump 4. The fine filter 7 is connected downstream of the second gear pump 6, and filters the melt discharged from the second gear pump 6.

[0032] The die 8 is connected downstream of the high-definition filter 7, and molds the molten material discharged from the high-definition filter 7 into a film, which is then conveyed to a forming roll (not shown) that follows, thereby producing an acrylic resin film.

[0033] The control device 9 controls the screw rotation speed N and the amount of raw material supplied to the extruder 3 Q so that the pressure of the melt between the extruder 3 and the first gear pump 4 is constant, and also controls the following (i), (ii), and (iii): (i) No control over Q (ii) When the fluctuation range of Q / N from the reference value exceeds a set value, Q is controlled so that the fluctuation range of Q / N is equal to or less than the set value, whereas when the fluctuation range of Q / N is equal to or less than the set value, Q is not controlled. (iii) The effect of controlling Q is reduced so that the pressure of the melt between the extruder 3 and the first gear pump 4 is kept constant. Execute one of the following:

[0034] According to the above configuration, N is controlled so that the pressure of the melt between the extruder 3 and the first gear pump 4 (hereinafter also referred to as the pressure on the discharge side of the extruder 3) is constant, and Q is not controlled or is controlled more loosely than N, so that the influence of the control of Q on the pressure on the discharge side of the extruder 3 can be reduced. In short, the inventors of the present application found that the response of the control of Q is slower than that of the control of N, and found that due to this delayed response of Q, it is difficult to stably control the pressure on the discharge side of the extruder 3 to be constant. Based on this knowledge, the inventors of the present application came up with the idea of ​​not controlling Q or controlling Q more loosely than N.

[0035] This makes it easy to stably control the pressure on the discharge side of the extruder 3 to a constant value, and makes it possible to maintain uniformity in quality, such as the thickness, of the acrylic resin film when it is produced from the molten material downstream of the first gear pump 4.

[0036] In addition, it is not necessary to control N and Q so that Q / N is constant, and N and Q may be controlled so that Q / N is not constant. In this way, it is not necessary to strictly control Q, and the pressure on the discharge side of the extruder 3 can be controlled more stably.

[0037] Here, the supply amount Q of the raw material corresponds to the measured value of the raw material measured by a measuring instrument. If Q is strictly controlled, a time lag occurs in the response of the measured value measured by the measuring instrument, and the response of the pressure on the discharge side of the extruder 3 becomes slower and stable control cannot be performed. In detail, the supply amount instruction value is distributed to each of the multiple measuring instruments at a ratio according to the raw material recipe based on the value of Q. If the value of Q fluctuates up or down, the instruction value to each measuring instrument will also fluctuate, and the raw material will be supplied to the extruder 3 at a ratio that is momentarily deviated from the raw material recipe due to the difference in the response of each measuring instrument. This causes the bulk density of the raw material to change, making the extruder 3 more susceptible to fluctuations (i.e., pressure fluctuations occur), and the raw material ratio is different from the originally designed ratio, causing a problem of deviation in product performance. In contrast, in the present application, as described above, Q is not strictly controlled, so the pressure on the discharge side of the extruder 3 can be more stably controlled.

[0038] <Preferable configuration of each component> (acrylic resin film) Examples of acrylic resins used in acrylic resin films include methacrylic resins (homopolymers of methacrylic acid esters and copolymers having the same as the main component). From the viewpoint of imparting impact resistance to the film, it is preferable that the acrylic resin is one in which rubber particles are blended, particularly methacrylic resin in which rubber particles are blended. The methacrylic resin is a homopolymer of methacrylic acid ester or a copolymer having the same as the main component. As the methacrylic acid ester, an alkyl ester of methacrylic acid is usually used, and the number of carbon atoms in the alkyl group is about 1 to 4. When a copolymer is used, an acrylic acid ester known to be advantageous as a copolymerization component of a methacrylic resin, or another polymerizable monomer copolymerizable with an alkyl methacrylate ester and / or an acrylic acid ester is used.

[0039] The methacrylic resin is preferably obtained by polymerization of monomers consisting of 50-100% by weight of a methacrylic acid alkyl ester having an alkyl group with 1-4 carbon atoms, 0-50% by weight of an acrylic acid ester, and 0-49% by weight of at least one other polymerizable monomer copolymerizable therewith. It is preferably a thermoplastic polymer having a glass transition temperature of 40°C or higher. Here, the acrylic acid ester is more preferably used in the range of 0.1-50% by weight, and the more preferable copolymerization ratio of the methacrylic acid alkyl ester is in the range of 50-99.9% by weight. The glass transition temperature of this methacrylic resin is more preferably 60°C or higher. In this specification, the term "monomer" refers not only to a case where the monomer is composed of one type of monomer, but also to a state where a plurality of monomers are mixed.

[0040] In this thermoplastic polymer, the alkyl methacrylate ester may be an alkyl methacrylate ester having an alkyl group with 1 to 8 carbon atoms. The alkyl group preferably has 1 to 4 carbon atoms. Among these, methyl methacrylate is particularly preferably used from the viewpoint of durability. The alkyl methacrylate ester may be used alone or in combination of two or more kinds. As the acrylic acid ester, an alkyl acrylate is usually used. As the alkyl acrylate, an alkyl acrylate having 1 to 8 carbon atoms in the alkyl group can be mentioned. The number of carbon atoms in the alkyl group is preferably 1 to 4. The acrylic acid ester may be used alone or in combination of two or more kinds.

[0041] Other polymerizable monomers copolymerizable with the methacrylic acid alkyl ester and / or acrylic acid ester include various monomers conventionally known in this field. Examples of such monomers include monofunctional monomers having one polymerizable carbon-carbon double bond in the molecule, and polyfunctional monomers having at least two polymerizable carbon-carbon double bonds in the molecule, and the monofunctional monomers are preferably used. Specific examples of monofunctional monomers include styrene-based monomers such as styrene, α-methylstyrene, vinyltoluene, halogenated styrene, and hydroxystyrene; vinyl cyanides such as acrylonitrile and methacrylonitrile; unsaturated acids such as acrylic acid, methacrylic acid, maleic anhydride, and itaconic anhydride; maleimides such as N-methylmaleimide, N-cyclohexylmaleimide, and N-phenylmaleimide; unsaturated alcohols such as methallyl alcohol and allyl alcohol; and other monomers such as vinyl acetate, vinyl chloride, ethylene, propylene, 4-methyl-1-pentene, 2-hydroxymethyl-1-butene, methyl vinyl ketone, N-vinylpyrrolidone, and N-vinylcarbazole.

[0042] Specific examples of polyfunctional monomers include polyunsaturated carboxylic acid esters of polyhydric alcohols such as ethylene glycol dimethacrylate, butanediol dimethacrylate, and trimethylolpropane triacrylate; alkenyl esters of unsaturated carboxylic acids such as allyl acrylate, allyl methacrylate, and allyl cinnamate; polyalkenyl esters of polybasic acids such as diallyl phthalate, diallyl maleate, triallyl cyanurate, and triallyl isocyanurate; and aromatic polyalkenyl compounds such as divinylbenzene.

[0043] Such other polymerizable monomers copolymerizable with the alkyl methacrylate ester and / or the acrylic ester may be used alone or in combination of two or more kinds.

[0044] As described above, the methacrylic resin is preferably a thermoplastic polymer obtained by polymerizing monomers consisting of 50 to 100% by weight, more preferably 50 to 99.9% by weight, of an alkyl methacrylate ester having an alkyl group having 1 to 4 carbon atoms, 0 to 50% by weight, more preferably 0.1 to 50% by weight, of an acrylic ester, and 0 to 49% by weight of at least one other polymerizable monomer copolymerizable therewith. A polymer falling within this range can be used alone or as a mixture of two or more polymers.

[0045] The methacrylic resin may have a ring structure in the polymer main chain, since it can increase the durability of the film. The ring structure is preferably a heterocyclic structure such as a cyclic acid anhydride structure, a cyclic imide structure, or a lactone ring structure. Specifically, cyclic acid anhydride structures such as glutaric anhydride structure and succinic anhydride structure; cyclic imide structures such as glutarimide structure and succinimide structure; lactone ring structures such as butyrolactone and valerolactone, etc. can be mentioned. The glass transition temperature of the methacrylic resin can be increased by increasing the ring structure content in the main chain. The cyclic acid anhydride structure or cyclic imide structure can be introduced into the main chain by a method of introducing by copolymerizing a monomer having a cyclic structure such as maleic anhydride or maleimide, a method of introducing a cyclic acid anhydride structure by a dehydration / demethanolization condensation reaction after polymerization, or a method of introducing a cyclic imide structure by reacting an amino compound.

[0046] The polymerization method of the thermoplastic polymer is not particularly limited, but may be a method such as ordinary suspension polymerization, emulsion polymerization, or bulk polymerization. In order to obtain a suitable glass transition temperature or a viscosity that exhibits suitable moldability into a film, it is preferable to use a chain transfer agent during polymerization. The amount of the chain transfer agent may be appropriately determined depending on the type and composition of the monomer.

[0047] The methacrylic resin may contain rubber particles in order to impart impact resistance to the film. The rubber particles preferably have an average particle size in the range of 0.05 to 0.4 μm, more preferably 0.06 to 0.3 μm, and particularly preferably 0.1 to 0.25 μm. The rubber particles are preferably contained in an amount of 3 to 60 parts by weight, more preferably 5 to 50 parts by weight, and further preferably 10 to 40 parts by weight, per 100 parts by weight of the total of the acrylic resin (eg, methacrylic resin) and the rubber particles.

[0048] The rubber particles are preferably a rubber-containing polymer obtained by polymerizing 100 parts by weight of an elastic copolymer having a layer obtained by polymerizing 50-99.9% by weight of an acrylic acid alkyl ester, 0-49.9% by weight of at least one other vinyl monomer copolymerizable therewith, and 0.1-10% by weight of a copolymerizable crosslinking monomer, in the presence of 100 parts by weight of an elastic copolymer having a layer obtained by polymerizing 10-400 parts by weight of a monomer consisting of 50-100% by weight of a methacrylic acid ester, 0-50% by weight of an acrylic acid ester, and 0-49% by weight of at least one other vinyl monomer copolymerizable therewith, to bond at least one polymerized layer from the latter monomer to the surface of the elastic copolymer. The rubber particles can be produced with different average particle sizes by changing the polymerization conditions.

[0049] This rubber-containing polymer can be obtained, for example, by the following method. The above components for the elastic copolymer are polymerized in at least one reaction stage by emulsion polymerization or the like to obtain an elastic copolymer. In the presence of the obtained elastic copolymer, the above-mentioned monomer containing methacrylic acid ester is polymerized in at least one reaction stage by emulsion polymerization or the like. By such multiple-stage polymerization, the monomer containing methacrylic acid ester used in the latter stage is graft-copolymerized to the elastic copolymer, and a crosslinked elastic copolymer having a graft chain is produced. That is, this rubber-containing polymer becomes a graft copolymer having a multi-layer structure containing an acrylic acid alkyl ester as the main component of rubber. In addition, when the polymerization of the elastic copolymer is performed in two or more stages, or when the polymerization of the monomer mainly composed of a methacrylic acid ester is performed in two or more stages, in either case, it is sufficient that the overall monomer composition is within the above range, not the monomer composition of each stage.

[0050] Examples of the alkyl acrylate in the rubber-containing polymer include those in which the alkyl group has a carbon number of 1 to 8. Among these, those in which the alkyl group has a carbon number of 4 to 8, such as butyl acrylate and 2-ethylhexyl acrylate, are preferred.

[0051] In the rubber-containing polymer, other vinyl monomers copolymerizable with the alkyl acrylate are preferably, for example, alkyl methacrylates such as methyl methacrylate, butyl methacrylate, and cyclohexyl methacrylate, styrene, acrylonitrile, and the like.

[0052] In the rubber-containing polymer, the copolymerizable crosslinkable monomer used to form the elastic copolymer may have at least two polymerizable carbon-carbon double bonds in one molecule. Examples of such crosslinkable monomers include unsaturated carboxylic acid diesters of glycols such as ethylene glycol dimethacrylate and butanediol dimethacrylate; alkenyl esters of unsaturated carboxylic acids such as allyl acrylate, allyl methacrylate, and allyl cinnamate; polyalkenyl esters of polyvalent carboxylic acids such as diallyl phthalate, diallyl maleate, triallyl cyanurate, and triallyl isocyanurate; unsaturated carboxylic acid esters of polyhydric alcohols such as trimethylolpropane triacrylate; and divinylbenzene. Among these, alkenyl esters of unsaturated carboxylic acids and polyalkenyl esters of polyvalent carboxylic acids are preferred. These crosslinkable monomers can be used alone or in combination of two or more types as necessary.

[0053] The elastic copolymer obtained by polymerization of the monomers mainly composed of acrylic acid alkyl esters as described above is grafted with monomers consisting of 50-100% by weight of methacrylic acid esters, 0-50% by weight of acrylic acid esters, and 0-49% by weight of at least one other vinyl monomer copolymerizable therewith. The methacrylic acid esters grafted to the elastic copolymer are preferably methacrylic acid alkyl esters, such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, and cyclohexyl methacrylate. Examples of acrylic acid esters that are copolymerized with these methacrylic acid esters as desired include acrylic acid alkyl esters such as methyl acrylate, butyl acrylate, and cyclohexyl acrylate. Examples of other vinyl monomers that can be copolymerized with methacrylic acid esters and / or acrylic acid esters include styrene and acrylonitrile.

[0054] The monomer to be grafted is preferably used in an amount of 10 to 400 parts by weight, more preferably 20 to 200 parts by weight, per 100 parts by weight of the elastic copolymer, and can be polymerized in at least one reaction stage. When the amount of the monomer to be grafted is 10 parts by weight or more, the elastic copolymer is less likely to aggregate, and the transparency is improved.

[0055] In addition, a hard layer mainly made of methacrylic acid ester can be provided inside the elastic copolymer layer. In this case, the monomer of the hard layer constituting the innermost layer is first polymerized. Then, in the presence of the obtained hard polymer, the monomer constituting the elastic copolymer is polymerized. Furthermore, in the presence of the obtained elastic copolymer, the monomer to be grafted mainly made of the methacrylic acid ester is polymerized. Here, the hard layer to be the innermost layer is preferably a polymerized monomer consisting of 70 to 100% by weight of methacrylic acid ester and 0 to 30% by weight of another vinyl monomer copolymerizable therewith. In this case, it is also effective to use a copolymerizable crosslinkable monomer as one of the other vinyl monomers. As the methacrylic acid ester, an alkyl methacrylate ester, particularly methyl methacrylate, is effective. Such a rubber-containing polymer having a three-layer structure is disclosed, for example, in JP-B-55-27576.

[0056] The average particle size of the rubber particles can be determined by observing with an electron microscope. For example, each rubber particle is mixed with a methacrylic resin to form a film, and the rubber component is dyed on the cross section with ruthenium oxide. After dyeing, the film is observed with an electron microscope, and the average particle size can be determined from the diameter of the dyed outer layer of the particle. Therefore, the particle size referred to here is the number average particle size.

[0057] The acrylic resin may contain common additives such as ultraviolet absorbers, organic dyes, inorganic dyes, pigments, antioxidants, antistatic agents, surfactants, etc. Among these, ultraviolet absorbers are preferably used in that they provide a film having excellent weather resistance for a long period of time.

[0058] These ultraviolet absorbents can be used alone or in combination of two or more kinds. The content of the ultraviolet absorbent is appropriately set according to the desired thickness of the acrylic resin extrusion film, and is usually 0.1 parts by weight or more, preferably 0.3 parts by weight or more, and usually 5 parts by weight or less, based on 100 parts by weight of the acrylic resin. The transmittance of the acrylic resin extrusion film having the desired thickness at a wavelength of 380 nm can be selected within a range in which it is preferably 25% or less, more preferably 15% or less, and even more preferably 5% or less. For example, in the case of a film having a thickness of 80 μm, in order to exhibit the same ultraviolet absorbing ability as the triacetyl cellulose film used as the acrylic resin film, it is preferable to set the amount of the ultraviolet absorbent to about 2.0 parts by weight based on the total of 100 parts by weight of the methacrylic resin and the rubber particles. It is preferable that the additives including these ultraviolet absorbents have a melting point of 180 ° C. or more in order to prevent the acrylic resin from evaporating as a volatile matter when the acrylic resin is discharged from the die and contaminating the roll or the like.

[0059] (Raw material feeder 2) Fig. 2 is a schematic diagram showing the raw material supplying machine 2. As shown in Fig. 2, the raw material supplying machine 2 has a first measuring machine 21 and a second measuring machine 22. All the measuring machines 21, 22 are connected to the extruder 3 via a transport pipe 25. The raw material of the acrylic resin film is fed into each of the measuring machines 21, 22 from a raw material chamber (not shown). The raw material includes a plurality of types of materials having different shapes.

[0060] Specifically, acrylic resin (PMMA) pellets are fed as a raw material into the first measuring device 21, and additives are fed as a raw material into the second measuring device 22. The raw material fed into the first measuring device 21 and the raw material fed into the second measuring device 22 have different shapes.

[0061] Each of the scales 21, 22 measures the weight of the respective raw materials, and sends the amount of raw material determined by the control device 9 to the extruder 3 via the transport pipe 25. That is, the control device 9 controls the amount of raw material supplied by controlling each of the scales 21, 22 as one control element in order to control the amount of molten material extruded from the extruder 3.

[0062] In this way, when multiple types of materials with different shapes are fed from the raw material feeder 2 into the extruder 3, pressure fluctuations are usually likely to occur at the discharge side of the extruder 3, but as described above, the first gear pump 4 and the second gear pump 6 are provided, so pressure fluctuations at the discharge side of the extruder 3 can be effectively reduced. The raw material may contain multiple types of materials with the same shape. The number of measuring devices may be increased or decreased.

[0063] (Extruder 3) Fig. 3 is a schematic diagram showing each member of the acrylic resin film production apparatus 1 except for the raw material supplying device 2. As shown in Fig. 3, the extruder 3 is a twin-screw extruder. The extruder 3 has a casing 30, a first screw 31 and a second screw 32 arranged in the casing 30, and a motor 35 that rotates and drives the first screw 31 and the second screw 32.

[0064] The casing 30 has an inlet 30a through which the raw material is introduced from the raw material supplying device 2. That is, the inlet 30a is connected to the transport pipe 25 of the raw material supplying device 2. Note that there may be a plurality of inlets 30a.

[0065] The first screw 31 and the second screw 32 are arranged parallel to each other and rotate in the same direction as each other as indicated by the arrows. Note that the first screw 31 and the second screw 32 may rotate in the opposite directions to each other.

[0066] The raw materials fed from the feed port 30a are mixed and sent downstream by the rotation of the first screw 31 and the second screw 32. At the same time, the raw materials being transported by the first screw 31 and the second screw 32 are melted by a heater (not shown) provided in the casing 30, resulting in the production of a molten material.

[0067] The motor 35 is controlled by the control device 9. That is, the control device 9 controls the motor 35 as one control element to control the rotation speeds of the first screw 31 and the second screw 32 in order to control the extrusion amount of the melt from the extruder 3.

[0068] As described above, since the extruder 3 is a twin-screw extruder, pressure fluctuations are more likely to occur at the tip than in a single-screw extruder. However, as described above, since the extruder 3 has the first gear pump 4 and the second gear pump 6, pressure fluctuations at the tip of the extruder 3 can be effectively reduced.

[0069] (First gear pump 4) As shown in FIG. 3, the first gear pump 4 has a first gear 41, a second gear 42, and a motor 45 that rotates the first gear 41 and the second gear 42. The first gear 41 and the second gear 42 mesh with each other and rotate in opposite directions as shown by the arrows. The melt extruded from the extruder 3 is sent downstream by the rotation of the first gear 41 and the second gear 42. At this time, the melt is pressurized by the first gear pump 4. That is, the value of the second pressure sensor 12 provided between the first gear pump 4 and the coarse filter 5 is larger than the value of the first pressure sensor 11 provided between the extruder 3 and the first gear pump 4. The pressure of the melt is increased by the first gear pump 4, for example, 5 MPa, and may be 3 MPa to 15 MPa.

[0070] As described above, according to the manufacturing apparatus of this embodiment, since it has the first gear pump 4, even if the extrusion amount of the molten material extruded from the extruder 3 fluctuates and the pressure of the molten material fluctuates, the first gear pump 4 can mitigate the pressure fluctuations of the molten material downstream of the first gear pump 4, and the molten material can be stably molded downstream of the high-definition filter 7.

[0071] (Coarse filter 5) As shown in FIG. 3, the coarse filter 5 is a filter having an opening size of, for example, 20 μm to 80 μm, and preferably 20 μm to 40 μm.

[0072] The mesh size of the coarse filter 5 is larger than that of the high-definition filter 7. This allows the molten material pressurized only by the first gear pump 4 to pass through the coarse filter 5. In other words, the first gear pump 4 only needs to increase the pressure of the molten material to pass through the coarse filter 5, so the amount of pressure increase of the molten material by the first gear pump 4 can be reduced.

[0073] The pressure of the molten material is reduced by passing through the coarse filter 5. That is, the reading of the third pressure sensor 13 provided between the second gear pump 6 and the coarse filter 5 becomes smaller than the reading of the second pressure sensor 11. The pressure reduction of the molten material by the coarse filter 5 is, for example, 5 MPa.

[0074] In this way, since the coarse filter 5 is provided between the first gear pump 4 and the second gear pump 6, even if the extrusion amount of the melt extruded from the extruder 3 fluctuates and the pressure of the melt fluctuates, the pressure fluctuation of the melt downstream of each can be mitigated by the coarse filter 5 in addition to the first gear pump 4 and the second gear pump 6, and molding of the melt can be more stably performed downstream of the high-definition filter 7. As a result, the uniformity of the quality of the acrylic resin film can be better maintained.

[0075] In addition, since the coarse filter 5 is provided between the first gear pump 4 and the second gear pump 6, even if pressure fluctuations occurring between the extruder 3 and the first gear pump 4 are propagated downstream, the coarse filter 5 can mitigate these pressure fluctuations.

[0076] Furthermore, since the coarse filter 5 is provided upstream of the high-definition filter 7, the durability of the high-definition filter 7 can be improved.

[0077] (Second gear pump 6) As shown in FIG. 3, the second gear pump 6 has a first gear 61, a second gear 62, and a motor 65 that rotates the first gear 61 and the second gear 62. The first gear 61 and the second gear 62 mesh with each other and rotate in opposite directions as shown by the arrows. The melt filtered by the coarse filter 5 is sent downstream by the rotation of the first gear 61 and the second gear 62. At this time, the melt is pressurized by the second gear pump 6. That is, the value of the fourth pressure sensor 14 provided between the second gear pump 6 and the fine filter 7 is larger than the value of the third pressure sensor 13. The pressure of the melt raised by the second gear pump 6 is, for example, 9 MPa, and may be 1 MPa to 15 MPa.

[0078] In this way, by having the second gear pump 6, even if the extrusion amount of the melt extruded from the extruder 3 fluctuates and the pressure of the melt fluctuates, the second gear pump 6 can mitigate the pressure fluctuations of the melt downstream of the second gear pump 6, and the melt can be stably molded downstream of the high-definition filter 7.

[0079] In addition, since the melt is pressurized by the first gear pump 4 and the second gear pump 6, the pressure difference between the front and rear of each gear pump can be reduced, thereby reducing backflow of the melt in each gear pump.

[0080] (High definition filter 7) As shown in FIG. 3, the high definition filter 7 is a polymer filter with an opening size of, for example, 0.5 μm to 30 μm, and preferably 1 μm to 10 μm.

[0081] The mesh size of the high-definition filter 7 is finer than that of the coarse filter 5. This allows the melt pressurized by the first gear pump 4 and the second gear pump 6 to pass through the fine-mesh high-definition filter 7. In other words, the melt needs to be highly pressurized to pass through the high-definition filter 7, but since the melt can be pressurized by both the first gear pump 4 and the second gear pump 6, the pressurization of the melt can be easily increased.

[0082] The pressure of the molten material is reduced by passing through the high-definition filter 7. That is, the numerical value of the discharge pressure from the high-definition filter 7 becomes smaller than the numerical value of the fourth pressure sensor 14. The numerical value of the discharge pressure from the high-definition filter 7 is the same as the numerical value of the discharge pressure from the die 8. The degree of pressure reduction of the molten material by the high-definition filter 7 can be selected according to the coarseness of the high-definition filter 7, the temperature and flow rate of the molten material, etc., and may be, for example, 7 MPa to 12 MPa.

[0083] (Die 8) 3, the die 8 is, for example, a T-die. The melt filtered by the high-definition filter 7 is formed into a sheet by the die 8. Thereafter, the sheet-like melt extruded from the discharge opening of the die 8 is conveyed to a forming roll (not shown) located below the discharge opening of the die 8, where it is cooled and solidified to produce an acrylic resin film.

[0084] (Control device 9) 2 and 3, the control device 9 controls the operation of each member. The control device 9 has a first control unit 91, a second control unit 92, and a raw material supply machine control unit 93.

[0085] The first control unit 91 receives a signal from the third pressure sensor 13 and sends a signal to the motor 45 of the first gear pump 4. Specifically, the first control unit 91 controls the motor 45 of the first gear pump 4 so that the resin pressure detected by the third pressure sensor 13 becomes constant, thereby controlling the rotation speed of the first gear pump 4.

[0086] The second control unit 92 receives the signal from the first pressure sensor 11, sends a signal to the motor 35 of the extruder 3, and further sends a signal of the supply amount Q to the raw material supplying machine control unit 93. The raw material supplying machine control unit 93 sends a signal of the set value of the supply amount Q based on the received signal of the supply amount Q to each of the measuring devices 21, 22 of the raw material supplying machine 2. In other words, the raw material supplying machine control unit 93 sends a signal to each of the measuring devices 21, 22 at a preset arbitrary ratio in response to the received signal of the supply amount Q.

[0087] In this way, the second control unit 92 performs feedback control on the rotation speed N of the first screw 31 and the second screw 32 of the extruder 3 and the supply amount Q of the raw material to the extruder 3. The control of the rotation speed N is performed by controlling the motor 35 of the extruder 3. The control of the supply amount Q is performed by controlling the measuring devices 21, 22 of the raw material supplying machine 2.

[0088] Specifically, the second control unit 92 controls N so that the pressure of the first pressure sensor 11 is constant, and also controls the following (i), (ii), and (iii): (i) No control over Q (ii) When the fluctuation range of Q / N from the reference value exceeds a set value, Q is controlled so that the fluctuation range of Q / N is equal to or less than the set value, whereas when the fluctuation range of Q / N is equal to or less than the set value, Q is not controlled. (iii) The effect of controlling Q is reduced so that the pressure of the first pressure sensor 11 becomes constant. Execute one of the following:

[0089] Here, the second control unit 92 may be preset to any one of the above (i), (ii), and (iii), or may be set to be able to select any one of the above (i), (ii), and (iii).

[0090] In the above (i), the second control unit 92 always turns off the control of Q. In other words, the second control unit 92 only controls N.

[0091] In the above (ii), the second control unit 92 controls Q when the fluctuation range of Q / N from the reference value exceeds the set value, but turns off the control of Q when the fluctuation range of Q / N is equal to or less than the set value. In other words, Q / N does not have to be a constant reference value. The reference value is a value that is predetermined for each manufacturing device. The fluctuation range refers to the absolute value of the difference from the reference value. For example, Q / N is in the range of 4.5 to 7.5, preferably in the range of 5.5 to 7.0, and more preferably in the range of 6.0 to 6.8. The appropriate range of Q / N varies depending on the size and specifications of the extruder.

[0092] In the above (iii), the second control unit 92 controls Q so that the pressure of the first pressure sensor 11 becomes constant, and at the same time controls Q so that the effect of the control of Q becomes weaker. Here, making the control of Q less effective means making the feedback control applied to Q less effective. Specifically, when the feedback control is PID control, "sluggish control" or "loose control" means that the gain values ​​set for each control item of proportional control (P), differential control (D), and integral control (I) are such that the fluctuation range of Q / N is within a specified range, and the control effect (response to control, etc.) is small. In (iii) above, a gain value is set for Q that reduces the effect of feedback control (makes control slow). This makes the response to control, etc. of Q slower.

[0093] According to this, the second control unit 92 controls N so that the pressure of the first pressure sensor 11 is constant, and does not control Q or controls Q more loosely than N, thereby reducing the effect of the control of Q on the pressure on the discharge side of the extruder 3. Therefore, it becomes easy to stably control the pressure on the discharge side of the extruder 3 to a constant value, and the uniformity of the quality of the acrylic resin film can be maintained.

[0094] Preferably, in the above (ii), Q is controlled by reducing the effectiveness of control of Q. This allows the control of Q to be loosened, so that the pressure on the discharge side of the extruder can be controlled more stably.

[0095] Preferably, in the above (iii), when the fluctuation range of Q / N from the reference value exceeds a set value, Q is further controlled so that the fluctuation range of Q / N is equal to or less than the set value. This allows the control of Q to be loosened, so that the pressure on the discharge side of the extruder can be controlled more stably.

[0096] The manufacturing apparatus of the present disclosure is not limited to the above-described embodiment, and the design can be modified without departing from the scope of the present disclosure. For example, the number of gear pumps or the number of filters can be increased or decreased.

[0097] <Manufacturing method> Next, one embodiment of a method for producing an acrylic resin film will be described with reference to Figs.

[0098] First, the raw material for the acrylic resin film is supplied from the raw material supplyer 2 to the extruder 3 (hereinafter referred to as the supplying step). Then, the raw material supplied from the raw material supplyer 2 is melted and kneaded in the extruder 3, and the molten material obtained by the melting and kneading is extruded to the downstream side of the extruder 3 (hereinafter referred to as the extrusion step). Then, the molten material extruded from the extruder 3 is pressurized by the first gear pump 4 connected to the downstream side of the extruder 3 (hereinafter referred to as the pressurizing step).

[0099] In the extrusion process, when the rotation speed of the screws 31 and 32 is N and the amount of the raw material supplied to the extruder 3 is Q, N is controlled so that the pressure of the melt between the extruder 3 and the first gear pump 4 is constant, and the following (i), (ii), and (iii) are satisfied. (i) No control over Q (ii) When the fluctuation range of Q / N from the reference value exceeds a set value, Q is controlled so that the fluctuation range of Q / N is equal to or less than the set value, whereas when the fluctuation range of Q / N is equal to or less than the set value, Q is not controlled. (iii) The effect of controlling Q is reduced so that the pressure of the melt between the extruder 3 and the first gear pump 4 is kept constant. Execute one of the following:

[0100] According to this, N is controlled so that the pressure of the melt between the extruder 3 and the first gear pump 4 is constant, and Q is not controlled or is controlled more loosely than N, thereby reducing the effect of controlling Q on the pressure on the discharge side of the extruder 3. Therefore, it becomes easy to stably control the pressure on the discharge side of the extruder 3 to a constant value, and the uniformity of the quality of the acrylic resin film can be maintained.

[0101] Preferably, in the above (ii), Q is controlled by reducing the effectiveness of control of Q. This allows the control of Q to be relaxed while maintaining the fluctuation range of Q / N at or below a set value, so that the pressure on the discharge side of the extruder 3 can be controlled more stably. The fluctuation range of Q / N can be set within a range of, for example, 4.5 to 7.5, preferably 5.5 to 7.0, and more preferably 6.0 to 6.8.

[0102] Preferably, in the above (iii), when the fluctuation range of Q / N from the reference value exceeds a set value, Q is further controlled so that the fluctuation range of Q / N becomes equal to or less than the set value. This allows the control of Q to be loosened while maintaining the fluctuation range of Q / N equal to or less than the set value, so that the pressure on the discharge side of the extruder 3 can be controlled more stably.

[0103] The manufacturing method of the present disclosure is not limited to the above-described embodiment, and can be modified without departing from the scope of the present disclosure. For example, the manufacturing method of the present disclosure is not limited to being realized by the manufacturing apparatus 1 of FIG. 1, and may be realized by other different apparatuses.

[0104] (Example) Next, an embodiment will be described.

[0105] [Example 1] (1) Preparation of raw resin As the methacrylic resin, pellets of a thermoplastic polymer (glass transition temperature 104°C) which is a copolymer of 97% by weight of methyl methacrylate and 3% by weight of methyl acrylate were used. As the acrylic rubber particles, those manufactured in the same manner as in Example 3 of the above-mentioned JP-B-55-27576 were used, which have a spherical three-layer structure consisting of an innermost layer of a hard polymer in which methyl methacrylate is copolymerized with a small amount of allyl methacrylate, an intermediate layer of an elastic polymer mainly composed of butyl acrylate and further copolymerized with styrene and a small amount of allyl methacrylate, and an outermost layer of a hard polymer in which methyl methacrylate is copolymerized with a small amount of methyl acrylate, and have an average particle diameter of 0.22 μm. 70 parts of methacrylic resin pellets and 30 parts of acrylic rubber particles were mixed in a super mixer, then melt-kneaded in a twin-screw extruder to form pellets of a resin composition, which were used as an acrylic resin.

[0106] (2) Preparation of acrylic resin film The obtained pellets were melted in another twin-screw extruder (extrusion temperature 230°C to 270°C), passed through a first gear pump, a coarse filter, a second gear pump, and a high-definition filter in this order, extruded from a die, and passed through a forming roll (surface temperature 60°C to 100°C) to obtain an acrylic resin film (width 1300mm to 2000mm) by appropriately adjusting the discharge amount and line speed so that the thickness becomes 80μm. Note that the pellets were pressurized in the first and second gear pumps under the following conditions. In the preparation of the acrylic resin film in this Example 1, control of Q and N (QN control) was not carried out in the extruder, that is, control of the raw material supply amount Q shown in the above (i) was not carried out.

[0107] [Comparative Example 1] An acrylic resin film was prepared in the same manner as in Example 1, except that feedback control was performed on the raw material supply amount Q according to the screw rotation speed N so that Q / N was constant at 6.5.

[0108] Next, Table 1 shows the measured values ​​of the first pressure sensor in Example 1 and Comparative Example 1.

[0109] [Table 1]

[0110] As shown in Table 1, the range between the maximum and minimum values ​​was smaller and the standard deviation was smaller in Example 1 than in Comparative Example 1. Thus, it was found that the measurement value of the first pressure sensor was more stable and constant in Example 1 than in Comparative Example 1. Therefore, in Example 1, the pressure on the discharge side of the extruder could be stably controlled to a constant value, so that the uniformity of the quality of the acrylic resin film could be maintained. [Explanation of symbols]

[0111] 1. Acrylic resin film manufacturing equipment 2 Raw material feeder 21,22 1st and 2nd measuring instrument 3. Extruder 31,32 1st and 2nd screws 35 Motor 4. First gear pump 41,42 1st and 2nd gears 45 Motor 5 Coarse Filter 6. Second gear pump 61,62 1st and 2nd gears 65 Motor 7 High-definition filters 8 Die 9. Control Device 91, 92 First and second control sections 93 Raw material supply machine control unit 11-14 1st to 4th pressure sensors

Claims

1. A supplying step of supplying a raw material for the acrylic resin film from a raw material supplying machine to an extruder; an extrusion step of melting and kneading the raw materials supplied from the raw material supplying device in the extruder, and extruding a molten material obtained by the melting and kneading to a downstream side of the extruder; a pressure increasing step of increasing the pressure of the molten material extruded from the extruder by a gear pump connected to the downstream side of the extruder; Equipped with The extruder includes a screw and a motor that rotates the screw. In the extrusion step, When the rotation speed of the screw is N and the amount of the raw material fed to the extruder is Q, N is controlled so that the pressure of the melt between the extruder and the gear pump is constant, and the following (i), (ii), and (iii) are satisfied: (i) Not controlling Q (ii) When the fluctuation range of Q / N from the reference value exceeds a set value, Q is controlled so that the fluctuation range of Q / N is equal to or less than the set value, whereas when the fluctuation range of Q / N is equal to or less than the set value, Q is not controlled. (iii) Controlling Q by reducing the effectiveness of control of Q so that the pressure of the melt between the extruder and the gear pump becomes constant. A method for producing an acrylic resin film, comprising carrying out any one of the steps described above.

2. The method for producing an acrylic resin film according to claim 1 , further comprising the step of controlling Q by reducing the effect of controlling Q in the step (ii).

3. 3. The method for producing an acrylic resin film according to claim 1 or 2, further comprising controlling Q so that, when the fluctuation range of Q / N from the reference value exceeds a set value, the fluctuation range of Q / N is equal to or less than the set value in the step (iii).

4. The method for producing an acrylic resin film according to claim 1 , wherein the extruder is a twin-screw extruder.

5. The method for producing an acrylic resin film according to claim 1 , wherein the raw material contains a plurality of types of materials having different shapes.

6. a feedstock supplying machine including a feedstock for an acrylic resin film; an extruder having a screw and a motor for rotating the screw, the extruder melting and kneading the raw material supplied from the raw material supplying device and extruding the raw material as a molten material; a gear pump connected downstream of the extruder to pressurize and discharge the molten material extruded from the extruder; When the rotation speed of the screw is N and the amount of the raw material fed to the extruder is Q, N is controlled so that the pressure of the melt between the extruder and the gear pump is constant, and the following (i), (ii), and (iii) are satisfied: (i) Not controlling Q (ii) When the fluctuation range of Q / N from the reference value exceeds a set value, Q is controlled so that the fluctuation range of Q / N is equal to or less than the set value, whereas when the fluctuation range of Q / N is equal to or less than the set value, Q is not controlled. (iii) Controlling Q by reducing the effectiveness of control of Q so that the pressure of the melt between the extruder and the gear pump becomes constant. A control device that executes any one of the above. An acrylic resin film manufacturing apparatus comprising:

7. The acrylic resin film production apparatus according to claim 6, wherein in the step (ii), Q is controlled by reducing the effectiveness of control of Q.

8. The acrylic resin film manufacturing apparatus according to claim 6 or 7, further comprising: controlling Q so that, when the fluctuation range of Q / N from the reference value exceeds a set value, the fluctuation range of Q / N is equal to or less than the set value in the step (iii).

9. The acrylic resin film production apparatus according to claim 6 , wherein the extruder is a twin-screw extruder.

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