JP4131091B2 - Method for producing thermoplastic resin composition - Google Patents

Description

【図面の簡単な説明】
【図１】本発明の製造方法の一実施形態により熱可塑性樹脂組成物を製造するための装置を模式的に示す図である。
【図２】本発明の製造方法の他の実施形態により熱可塑性樹脂組成物を製造するための装置を模式的に示す図である。
【図３】実施例１で熱可塑性樹脂組成物を製造したときに用いた装置を模式的に示す図である。
【図４】実施例２で熱可塑性樹脂組成物を製造したときに用いた装置を模式的に示す図である。
【図５】（Ａ）、（Ｂ）、（Ｃ）は、それぞれ実施例１、実施例２、および比較例１で製造した熱可塑性樹脂組成物の断面拡大顕微鏡写真である。
【符号の説明】
１ 混合機
２ 押出機
３ 水槽
４ カッター
５ 液化二酸化炭素ボンベ
６ 二酸化炭素用定量ポンプ
７ 保圧弁
８ 添加剤供給部
９ 熱可塑性樹脂（Ａ）
１０ 熱可塑性樹脂（Ｂ）
１１ ホッパー
１２ ヒーター
１３、２５、２６、２７、２８ 圧力ゲージ
１４ 脱気口
１５ ダイ
１６ ペレット
１７ 低分子有機化合物槽
１８ 低分子有機化合物用定量ポンプ
１９ 低分子有機化合物ライン
２０ 二酸化炭素ライン
２１ 第１押出機
２２ 第２押出機
２３ 第３押出機
２４ 冷媒循環器
２５ 質量流量計[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a thermoplastic resin composition by mixing two or more kinds of thermoplastic resins in a molten state in the presence of carbon dioxide.
[0002]
[Prior art]
In recent years, the performance required for thermoplastic resin materials has become sophisticated and diversified, and it has become difficult to satisfy these needs with a single thermoplastic resin material. Therefore, research and development have been actively conducted in order to meet various needs as a multi-component thermoplastic resin material by combining several types of thermoplastic resins having different properties. These techniques are called polymer blends, polymer alloys, polymer composites and the like. Especially, the method of melt-mixing 2 or more types of thermoplastic resins in an extruder, and manufacturing a thermoplastic resin composition is a well-known technique, and is implemented industrially using this method. The above method can be carried out relatively easily, has a great merit that it is continuous production and is low in cost.
[0003]
However, the above method has some problems as described below.
(A) When the melting temperature and the melt viscosity between different thermoplastic resins are significantly different, they cannot be uniformly dissolved and dispersed.
(B) When the compatibility between different types of thermoplastic resins is poor, a compatibilizing agent such as a block copolymer or a graft copolymer is generally added to reduce the interfacial tension. However, it is difficult to design and select a compatibilizing agent, and there are many examples of performance deterioration due to the addition of the compatibilizing agent.
(C) When melt blending at a high temperature is required, there is a possibility of performance deterioration due to decomposition or the like, and there are many examples that lead to performance deterioration due to the influence of plasticizer addition.
From the above, it is known that the melt mixing technique using an extruder can be easily carried out, but is greatly restricted by the thermoplastic resin material used.
[0004]
[Problems to be solved by the invention]
The problem of the present invention is that when different types of thermoplastic resins are melted and mixed, there is almost no restriction on the thermoplastic resin material to be used, and no compatibilizer or plasticizer that adversely affects the physical properties of the product is used. Even a finely dispersed structure can be achieved, and a resin composition having a finely dispersed structure made of a heterogeneous incompatible thermoplastic resin, which has been impossible with the conventional melt-mixing method, is easily produced at low cost. It is providing the manufacturing method of the thermoplastic resin composition which can be manufactured well.
[0005]
[Means for Solving the Problems]
  This invention is the manufacturing method of the following thermoplastic resin composition.
  (1) In producing a thermoplastic resin composition by mixing two or more thermoplastic resins in an extruder in a molten state,
  Using a multistage extruder with 3 or more extruders connected,
  In the first extruderAddition of 2-200 parts by weight of carbon dioxide in a supercritical state with respect to 100 parts by weight of the total amount of the thermoplastic resinAnd
  Advance the fine dispersion of the molten mixture in the second extruder,
  Degassing carbon dioxide with the third extruderDo
  A method for producing a thermoplastic resin composition.
  (2)In the first extruderFurthermore, at least one kind of a low molecular weight compound having 1 to 6 carbon atoms selected from the group consisting of alcohols, alkanes, carboxylic acids, ethers, ketones and benzene with respect to 100 parts by weight of the total amount of the thermoplastic resin The method for producing a thermoplastic resin composition as described in (1) above, wherein the organic compound is added at a ratio of 0.01 to 50 parts by weight.
  (3) The method for producing a thermoplastic resin composition as described in (2) above, wherein the low molecular organic compound is ethanol.
  (4)In the first extruderA step of heating and melting and mixing two or more thermoplastic resins;
  In the first extruderAdding carbon dioxide to a molten mixture of two or more thermoplastic resins at a pressure of 3-50 MPa;
  In the second extruderA step of mixing two or more thermoplastic resins in a molten state in the presence of carbon dioxide;
  In the third extruderDegassing carbon dioxide and
  The manufacturing method of the thermoplastic resin composition in any one of said (1)-(3) containing.
  (5) The method for producing a thermoplastic resin composition according to any one of (1) to (4), wherein the extruder is a single-screw extruder.
[0006]
  The greatest feature of the method for producing the thermoplastic resin of the present invention is:Using a multi-stage extruder with 3 or more extruders connected,2 to 200 parts by weight, preferably 3 to 150 parts by weight with respect to 100 parts by weight of the total amount of thermoplastic resins in which carbon dioxide in a supercritical state is mixed as a medium when two or more kinds of thermoplastic resins are melt-mixed in an extruder. Parts by weight, more preferably 5-100 parts by weightThen, fine dispersion of the molten mixture proceeds with the second extruder, and carbon dioxide is degassed with the third extruder.It is to be.
  By adding carbon dioxide at the above ratio, when melted and mixed, the melt viscosity of the thermoplastic resin melt decreases as a whole. As a result, the difference in melt viscosity between dissimilar thermoplastic resins is reduced, the uniform dispersibility is greatly improved, melt blending at a lower temperature is possible, and the possibility of product performance deterioration due to decomposition and the like is small. The effect becomes. In addition, since there is no need to add a compatibilizing agent or a plasticizer, there is no worry about deterioration of physical properties of the product. Further, when removing carbon dioxide added after melting and mixing, there is an effect of removing impurities in the resin depending on the case.
  The above synergistic effect makes it possible to produce polymer blends in which different types of incompatible thermoplastic resins that were previously impossible by melt-mixing are uniformly finely dispersed. A functional thermoplastic resin composition can be obtained.
[0007]
Further, as another embodiment of the present invention, there is an embodiment in which a low molecular organic compound is added together with carbon dioxide. That is, by adding a low molecular weight organic compound as an auxiliary agent together with carbon dioxide, the dispersion state of the resulting thermoplastic resin composition may become more uniform and fine. This is presumed that the low-molecular organic compound exhibits a kind of compatibilizing effect.
When adding a low molecular weight organic compound, the addition amount is preferably 0.01 to 50 parts by weight and more preferably 0.1 to 20 parts by weight per 100 parts by weight of the total amount of the thermoplastic resin. Moreover, it is preferable that it is 50 weight% or less among the total amount with a carbon dioxide, and it is more preferable that it is 0.01-30 weight%.
[0008]
  The state at the time of addition of carbon dioxide used in the present invention is a supercritical state. Adding in supercritical state is used for melt mixingFirst 1 ExtruderIt is preferable from the viewpoint that carbon dioxide can be added quantitatively, stably, and in a large amount. The added carbon dioxide is considered to be in a state of being dissolved and diffused in the molten mixture of the thermoplastic resin.
[0009]
  As a low molecular organic compound used in the present inventionIsAt least one low molecular weight organic compound having 1 to 6 carbon atoms selected from the group consisting of alcohols, alkanes, carboxylic acids, ethers, ketones and benzene,used. In particular, ethanol is preferable from the viewpoint of safety for human bodies and foods. Furthermore, among ethanol, from the viewpoint of cost reduction, per se known modified ethanol which is usually used for industrial use is preferable. Examples of denaturing agents for denatured ethanol include known ones such as methanol, lactic acid, benzene, and ether.
[0010]
The thermoplastic resin used in the present invention can be used without any particular limitation. Here, the thermoplastic resin is a concept including not only a hard resin but also a soft resin. Examples of the thermoplastic resin include low density polyethylene, high density polyethylene, linear low density polyethylene, ultrahigh molecular weight polyethylene, ethylene-propylene copolymer, ethylene-butene copolymer, propylene-butene copolymer, ethylene-methacrylic acid copolymer, ethylene. -Acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ionomer resin (for example, ethylene-methacrylic acid copolymer ionomer resin), polypropylene, ultrahigh molecular weight polypropylene, polybutene, 4-methylpentene-1 resin, cyclic Polyolefin resin, ethylene-styrene copolymer, styrene resin (polystyrene, butadiene-styrene copolymer (HIPS), acrylonitrile-styrene copolymer) (AS resin), acrylonitrile-butadiene-styrene copolymer (ABS resin, etc.), polyvinyl chloride, polyvinylidene chloride, polycarbonate, polyacetal, polyphenylene oxide, polyvinyl acetate, polyvinyl alcohol, polymethyl methacrylate, cellulose acetate, polyester (Eg, polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, etc.), polyamide resin, polyimide resin, fluororesin, polysulfone, polyethersulfone, polyarylate, polyetheretherketone, liquid crystal polymer, thermoplastic polyurethane, thermoplastic elastomer Biodegradable polymers (for example, hydroxycarboxylic acid condensates such as polylactic acid, diaus such as polybutylene succinate) Condensates) and the like of carboxylic acids and.
[0011]
In the present invention, as already described, two or more thermoplastic resins are used. In this case, the composition ratio of each component composed of two or more thermoplastic resins constituting the resin composition of the present invention is an arbitrary ratio. In the present invention, for example, a good fine dispersion structure can be achieved by mixing each component to be blended at an arbitrary ratio using carbon dioxide as a medium.
[0012]
In the present invention, as long as the achievement of the problem is not impaired, the resin composition, if necessary, pigments, dyes, lubricants, antioxidants, fillers, stabilizers, flame retardants, antistatic agents, An ultraviolet ray preventive agent, a crosslinking agent, an antibacterial agent, a crystal nucleating agent, a shrinkage preventing agent, a foaming nucleating agent, a foaming aid and the like can be added.
[0013]
  In the present invention, a method for melting and mixing a thermoplastic resinIsExtrusion molding, injection moldingShape etc.Used in molding methodsMultistage extruderCan be adopted. Especially used for extrusion moldingMultistageThe use of an extruder is preferred. The thermoplastic resin composition of the present invention isIn the first extruderOnce two or more kinds of thermoplastic resins are melted and mixed in the presence of carbon dioxide by an apparatus such as an extruder,Advance the fine dispersion of the molten mixture in the second extruder,After removing carbon dioxide, it is cooled and molded into a pellet, for example, to obtain a thermoplastic resin composition, and then molded by a desired molding method to obtain a molded product. Alternatively, two or more thermoplastic resins are melted and mixed in the presence of carbon dioxide in a molding machine used for the desired molding method, and the carbon dioxide is removed to obtain a thermoplastic resin composition, which is then cooled. Alternatively, the thermoplastic resin composition in a molten state can be molded as it is with a molding machine to form a molded product. In any case, melting and mixing of two or more thermoplastic resinsUsing a multi-stage extruder in which three or more extruders are connected, carbon dioxide in a supercritical state is added at a ratio of 2 to 200 parts by weight with respect to a total amount of 100 parts by weight of the thermoplastic resin in the first extruder. Then, the dispersion of the molten mixture is advanced by the second extruder, and the third extruderExcept for removing carbon dioxide, the same method as the conventional melting and mixing method can be adopted.
[0014]
  The melting and mixing of the thermoplastic resin is preferably carried out under a high pressure state in which a large amount of carbon dioxide is dissolved and diffused in the thermoplastic resin. Such a high pressure condition is caused by a molten thermoplastic resin.MultistageFormed by filling in an extruder, such as a single screw extruderMultistageThis is easily realized by using an extruder.
[0015]
  The following method can be illustrated as a preferable manufacturing method of a thermoplastic resin composition. FirstIn the first extruderAfter two or more kinds of thermoplastic resins are supplied to the extruder and heated and melted, carbon dioxide is added to the molten thermoplastic resin in the extruder at a pressure of 3 to 50 MPa, preferably 10 to 30 MPa,In the second extruderTwo or more thermoplastic resins are melted and mixed in the presence of carbon dioxide.To advance the fine dispersion of the molten mixtureAfter forming the thermoplastic resin compositionIn the third extruderCarbon dioxide from the thermoplastic resin composition is optionally degassed with impurities in the thermoplastic resin.
  The temperature and time for melting and mixing are appropriately set mainly depending on the type, combination, mixing ratio, amount of carbon dioxide added, desired physical properties of the desired thermoplastic resin composition, equipment used, etc. However, a temperature range in which the thermoplastic resin does not melt and decompose is selected, and a time in which two or more thermoplastic resins are sufficiently uniformly dispersed is selected. Such temperature and time can be determined experimentally once the above factors are determined.
[0016]
In the present invention, impurities that can be removed together with carbon dioxide are monomer residues, solvents, water, and the like contained in the thermoplastic resin. For example, in the case of polyethylene, ethylene monomers are used.
[0017]
When adding a low molecular organic compound as an auxiliary agent together with carbon dioxide, the low molecular organic compound supply line may be connected to the carbon dioxide supply line and supplied to the thermoplastic resin melted with carbon dioxide, You may supply separately from a carbon dioxide. The supplied low molecular weight organic compound can be removed together with the removal of carbon dioxide.
[0018]
  The extruder used isIf it is a multistage extruder with 3 or more extruders connectedThere is no restriction in particular, well-known used for resin processing methodMultistageAn extruder can be used. For example, a single screw extruder with one screw, a twin screw extruder with two screws, and a multi-screw extruder with three or more screwsMachineThere is no particular limitation.
  Among these, a single screw extruder is preferable. In the single screw extruder, the inside of the extruder is completely filled with the molten thermoplastic resin, so that the resin pressure is easily maintained at a high pressure as compared with the twin screw extruder. In order to completely dissolve and diffuse a large amount of carbon dioxide in the thermoplastic resin, a high pressure state is required. Therefore, a single screw extruder that can easily maintain the resin pressure at a high pressure state is preferable for the production method of the present invention. Moreover, what has the supply port which supplies a carbon dioxide, and the deaeration port for removing a carbon dioxide is preferable.
[0019]
  In the supercritical stateThe carbon dioxide supply method is not particularly limited, and a known method can be adopted.The ThisHere, the supercritical state means that the pressure and temperature are above the critical point, and in the case of carbon dioxide, the pressure is 7.4 MPa or higher and the temperature is 31.35 ° C. or higher.
[0020]
The thermoplastic resin composition produced by the method of the present invention is obtained by mixing each component using carbon dioxide as a medium, and has a phase structure composed of a sea phase and an island phase (sea-island structure), or spinodal. It is preferably a continuous structure formed in the initial stage of decomposition (a continuous structure in which each thermoplastic resin is mixed in a network). In the case of a sea-island structure, the average particle size of the island phase portion is preferably 5 μm or less, and more preferably 1 μm or less. In this case, for example, the mechanical properties are excellent.
[0021]
The thermoplastic resin composition of the present invention can be used after being molded into various molded articles. As the molding method that can be applied, any of the conventionally known molding methods can be applied without limitation. For example, extrusion molding (sheet molding, inflation molding, foam molding, heterogeneous molding, multilayer molding, hollow molding, pipe molding). Etc.), injection molding and the like. The shape of the molded body is not particularly limited, such as powder, pellet, film, net, sheet, rod, filament, pipe, tube, plate, square, column, and the like.
Further, since the thermoplastic resin composition obtained by the method of the present invention has different thermoplastic resins uniformly and finely dispersed, it can have the respective characteristics of different thermoplastic resins without losing strength. It can be used as a new material in various fields by combining different types of thermoplastic resins.
[0022]
【The invention's effect】
  According to the method for producing a thermoplastic resin composition of the present invention, when different types of thermoplastic resins are melted and mixed in an extruder,Using a multi-stage extruder in which three or more extruders are connected, with respect to 100 parts by weight of the total amount of the thermoplastic resin in the first extruder,Carbon dioxide in the supercritical stateIt is added at a ratio of 2 to 200 parts by weight, fine dispersion of the molten mixture is advanced by the second extruder, and carbon dioxide is degassed by the third extruder.Therefore, it is possible to achieve a finely dispersed structure without using compatibilizers or plasticizers that adversely affect physical properties, and heat of dissimilar incompatibility that has been impossible with conventional melt mixing methods. A resin composition having a good fine dispersion structure made of a plastic resin can be easily and efficiently produced at a low cost.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
One embodiment (first embodiment) of the production method of the present invention will be described with reference to FIG.
In FIG. 1, 1 is a mixer, 2 is an extruder, 3 is a water tank, 4 is a cutter, 5 is a liquefied carbon dioxide cylinder, 6 is a metering pump for carbon dioxide, 7 is a pressure holding valve, and carbon dioxide is the extruder 2 It is comprised so that it can supply in the extruder 2 from the additive supply part 8 provided in this.
[0024]
In order to produce a thermoplastic resin composition using the apparatus shown in FIG. 1, the thermoplastic resin (A) 9 that becomes the sea phase of the sea-island structure and the thermoplastic resin (B) 10 that becomes the island phase are unmelted by the mixer 1. Then, the mixture is fed from the hopper 11 into the extruder 2, kneaded and melted.
[0025]
On the other hand, while the carbon dioxide in the liquefied carbon dioxide cylinder 5 is maintained in a liquid state, it is injected into the carbon dioxide metering pump 6 through the valve V1, and the discharge pressure of the carbon dioxide metering pump 6 is changed to the critical pressure of carbon dioxide ( 7.4 MPa) to 50 MPa, controlled by the pressure-holding valve 7 to discharge at a constant pressure, then heated by the heater 12 and added to the extruder 2 via the valve V2 in a supercritical state. It is supplied from the agent supply unit 8 into the extruder 2. The amount of carbon dioxide added is 2 to 200 parts by weight with respect to 100 parts by weight of the total amount of the thermoplastic resin. By supplying carbon dioxide in this way, the molten thermoplastic resin composition and carbon dioxide are mixed, and carbon dioxide is dissolved and diffused in the thermoplastic resin composition.
[0026]
From the viewpoint of adding carbon dioxide at a pressure of 3 to 50 MPa, the resin pressure (measured by the pressure gauge 13) of the zone for supplying carbon dioxide at this time is preferably in the range of 3 to 50 MPa. Setting the resin pressure to 3 MPa or more is preferable from the viewpoint of dissolving and diffusing carbon dioxide in the thermoplastic resin composition. Moreover, it is preferable to make the resin pressure 50 MPa or less from the viewpoint of safety in production.
[0027]
The screw shape of the extruder 2 is not particularly limited as long as the thermoplastic resin composition is already melted before reaching the additive supply unit 8. In particular, a screw provided with a ring having a small clearance from the barrel, Unimelt or the like in front of the additive supply unit 8 is preferable. If the added amount of carbon dioxide is an appropriate amount and the thermoplastic resin composition is in a completely molten state, no back flow of carbon dioxide to the hopper 11 side occurs due to melt sealing of the molten resin itself.
[0028]
The molten thermoplastic resin composition in which carbon dioxide is dissolved and diffused is finely dispersed in the thermoplastic resin (A) 9 in the downstream portion of the extruder 2 set to a temperature suitable for melt mixing. To advance. The temperature in the extruder 2 varies depending on the type of thermoplastic resin, the combination of thermoplastic resins, the mixing ratio, the amount of carbon dioxide added, the desired physical properties of the desired thermoplastic resin composition, the equipment used, and the like. The temperature is preferably in the range of 50 to 400 ° C.
[0029]
Carbon dioxide is degassed from the degassing port 14 before the composition is extruded through the die 15 from the thermoplastic resin composition melt-mixed in the extruder 2.
[0030]
The thermoplastic resin composition from which carbon dioxide has been degassed and removed is extruded in a strand form through a die 15 connected to the outlet of the extruder 2. The extruded thermoplastic resin composition can be cooled in the water tank 3 and then cut with a cutter 4 to obtain pellets 16 of the thermoplastic resin composition.
[0031]
In FIG. 1, carbon dioxide is removed before extrusion from the die 15, but it is not completely removed, and a thermoplastic resin composition can be obtained as a foam by using a part as a foaming agent.
In FIG. 1, one additive supply unit 8 is shown, but a plurality of additive supply units 8 may be provided. A plurality of deaeration ports 14 can also be provided. Further, although one extruder is used in FIG. 1, a tandem extruder in which two extruders are connected, or a multistage extruder in which three or more extruders are connected can also be used. For example, the carbon dioxide is supplied by the first extruder, the fine dispersion of the molten mixture is advanced by the second extruder, and the carbon dioxide is degassed by the third extruder. It is also possible.
[0032]
Another embodiment (second embodiment) of the production method of the present invention will be described with reference to FIG.
In FIG. 2, 1 is a mixer, 2 is an extruder, 3 is a water tank, 4 is a cutter, 5 is a liquefied carbon dioxide cylinder, 6 is a carbon dioxide metering pump, 7 is a pressure holding valve, 17 is a low molecular organic compound tank, Reference numeral 18 denotes a low-molecular organic compound metering pump configured to supply carbon dioxide and a low-molecular organic compound into the extruder 2 from an additive supply unit 8 provided in the extruder 2.
[0033]
In order to produce a thermoplastic resin composition using the apparatus shown in FIG. 2, first, a thermoplastic resin A9 as a sea phase and a thermoplastic resin B10 as an island phase are mixed in a non-melted state by the mixer 1, and then from the hopper 11. It is fed into the extruder 2, heated and kneaded and melted.
[0034]
On the other hand, while maintaining the carbon dioxide in the liquefied carbon dioxide cylinder 5 in a liquid state, it is injected into the carbon dioxide metering pump 6 through the valve V1, and the discharge pressure of the carbon dioxide metering pump 6 is changed to the critical pressure of carbon dioxide ( (7.4 MPa) to 50 MPa, the pressure is controlled by the pressure-holding valve 7 so as to be a constant pressure, and sent to the extruder 2. On the other hand, from the low molecular organic compound tank 17, the low molecular organic compound metering pump 18 sends and joins the low molecular organic compound from the low molecular organic compound line 19 to the carbon dioxide line 20. Carbon dioxide and a low molecular organic compound are merged and mixed, and then supplied into the extruder 2 from the additive supply unit 8 provided in the extruder 2 via the valve V2. The amount of the low-molecular organic compound added is preferably 0.01 to 50 parts by weight, more preferably 0.1 to 20 parts by weight, based on 100 parts by weight of all thermoplastic resins. In addition, the addition method of the low molecular organic compound includes, in addition to this, a method of directly supplying to the molten thermoplastic resin, a method of adding to the thermoplastic resin composition before supplying to the extruder 2 and uniformly mixing, etc. It is not limited. By supplying carbon dioxide and a low molecular weight organic compound in this way, the molten thermoplastic resin composition is mixed with carbon dioxide and a low molecular weight organic compound, and carbon dioxide and a low molecular weight organic compound are mixed in the thermoplastic resin composition. The compound dissolves and diffuses. Other operation methods and conditions are substantially the same as those of the first mode described with reference to FIG.
[0035]
3 shows a modification of the apparatus of FIG. 1, and FIG. 4 shows a modification of the apparatus of FIG. 3 and FIG. 4, a multistage extruder including a first extruder 21, a second extruder 22, and a third extruder 23 is used instead of the extruder 2 shown in FIGS. 1 and 2, respectively. A refrigerant circulator 24 is provided between the cylinder 5 and the carbon dioxide determination pump 6. A mass flow meter 25 and a pressure gauge 26 are provided on the discharge side of the pump 6, and pressure gauges 27 and 28 are provided in the first and second extruders.
[0036]
【Example】
Next, the present invention will be described from examples and comparative examples. The average island phase particle size and tensile elongation shown in Table 1 were measured according to the following method.
[0037]
・ Average island phase particle size
A thermoplastic resin composition was continuously produced by extrusion molding, and three sample pellets were obtained every 30 minutes. The cross section of three sample pellets was photographed with a transmission electron microscope. Each cross-sectional photograph was image-processed, the equivalent circle diameter was measured for the particle size of the island phase in a 500 μm square, and the average equivalent circle diameter was calculated. The average value of the average equivalent circle diameter at three points was defined as the average island phase particle size.
・ Tensile elongation
A test piece was prepared from the thermoplastic resin composition, and the tensile elongation was measured according to JIS K 7161.
[0038]
Example 1
A thermoplastic resin composition was produced using the apparatus shown in FIG. As the mixer 1, a Henschel mixer was used, and as the extruder, a multi-stage extruder having a first extruder 21 having a screw diameter of 20 mm, a second extruder 22 having a screw diameter of 30 mm, and a third extruder 23 was used. The additive supply unit 8 was provided in the vicinity of the center of the screw of the first extruder 21, and the deaeration port 14 was provided in one place in the third extruder 23.
[0039]
First, 90 parts by weight of low density polyethylene (LDPE) (Mirason 141, trade name, manufactured by Mitsui Chemicals) as the thermoplastic resin (A) 9 and polystyrene (PS) (Nippon Polystyrene Co., Ltd.) as the thermoplastic resin (B) 10 10 parts by weight of G120K (trademark) manufactured by Gluing Co., Ltd. was thoroughly mixed in the mixer 1 without being melted to obtain a mixture.
[0040]
Next, this mixture was supplied from the hopper 11 to the first extruder 21 and dissolved by heating at 200 ° C. Carbon dioxide was extracted directly from the liquid phase portion using a siphon type liquefied carbon dioxide cylinder 5. The flow path from the cylinder 5 to the carbon dioxide metering pump 6 is cooled with an ethylene glycol aqueous solution adjusted to −12 ° C. using the refrigerant circulator 24, and the carbon dioxide is sent to the carbon dioxide metering pump 6 in a liquid state. I was able to do it. Next, the carbon dioxide metering pump 6 is controlled while directly confirming with the mass flow meter 25 so that the liquid carbon dioxide sent is 0.3 kg / hour, and the discharge pressure (pressure gauge) of the carbon dioxide metering pump 6 is controlled. Pressure measurement valve 7 was adjusted to 30 MPa.
[0041]
Next, the line from the pressure holding valve 7 to the additive supply unit 8 of the first extruder 21 was heated by the heater 12 so as to be 50 ° C., and carbon dioxide was supplied into the first extruder 21. The molten resin pressure (measured with the pressure gauge 27) of the additive supply unit 8 at this time was 15 MPa. That is, the carbon dioxide immediately before being dissolved in the molten thermoplastic resin 11 is carbon dioxide in a supercritical state where the temperature is 50 ° C. or higher and the pressure is 15 MPa.
[0042]
Thus, supercritical carbon dioxide was supplied to the first extruder 21 at a ratio of 11 parts by weight with respect to 100 parts by weight of the total amount of the molten thermoplastic resin, and was uniformly dissolved and diffused by the screw. Next, this molten mixture was sent to the second extruder 22 in which the extruder cylinder temperature was adjusted to 140 ° C. and the resin pressure (measured with the pressure gauge 28) was adjusted to 20 MPa. The thermoplastic resin composition produced by melting and mixing in the second extruder 22 is transferred to the third extruder 23 whose extruder cylinder temperature is set to 160 ° C., and carbon dioxide is reduced in pressure from the degassing port 14. Was degassed.
[0043]
The thermoplastic resin composition from which carbon dioxide had been degassed was extruded in a strand form at an extrusion rate of 2.7 kg / hour through a die 15 connected to the outlet of the third extruder 23. The extruded strand-shaped thermoplastic resin composition was cooled in the water tank 3 and then cut by the cutter 4 to obtain pellets 16 of the thermoplastic resin composition.
As shown in FIG. 5A, which is a cross-sectional enlarged micrograph, the obtained thermoplastic resin composition has a PS phase (island phase) dispersed in LDPE (sea phase), and the average island phase grain The diameter was 0.5 μm.
[0044]
Example 2
A thermoplastic resin composition was produced using the apparatus shown in FIG. Ethanol as a low molecular weight organic compound is 3 weights with respect to 100 parts by weight of the total amount of low density polyethylene (LDPE) (Mirason 141, trade name, manufactured by Mitsui Chemicals) and polystyrene (PS) (G120K, trade name, manufactured by Nippon Polystyrene). The ratio was fed to the first extruder 21. The supply of the low molecular organic compound (ethanol) 17 was performed by feeding and joining the low molecular organic compound line 19 from the low molecular organic compound line 19 to the carbon dioxide line 20 by the low molecular organic compound quantitative pump 18. The supplied low molecular organic compound was deaerated from the deaeration port 14 together with carbon dioxide. Except these, it carried out similarly to Example 1 and manufactured the thermoplastic resin composition.
In the obtained thermoplastic resin composition, as shown in FIG. 5B which is a cross-sectional enlarged micrograph, the PS phase (island phase) is dispersed in LDPE (sea phase), and the average island phase grain The diameter was 0.2 μm.
[0045]
Comparative Example 1
It carried out like Example 1 except not supplying a carbon dioxide. In the obtained thermoplastic resin composition, as shown in FIG. 5C which is a cross-sectional enlarged micrograph, the PS phase (island phase) is dispersed in LDPE (sea phase), and the average island phase grains The diameter was 6.0 μm.
[0046]
The results of Examples and Comparative Examples are shown in Table 1.
[Table 1]

[Brief description of the drawings]
FIG. 1 is a diagram schematically showing an apparatus for producing a thermoplastic resin composition according to an embodiment of the production method of the present invention.
FIG. 2 is a view schematically showing an apparatus for producing a thermoplastic resin composition according to another embodiment of the production method of the present invention.
3 is a view schematically showing an apparatus used when a thermoplastic resin composition is produced in Example 1. FIG.
4 is a view schematically showing an apparatus used when a thermoplastic resin composition is produced in Example 2. FIG.
5 (A), (B), and (C) are cross-sectional magnified photomicrographs of the thermoplastic resin compositions produced in Example 1, Example 2, and Comparative Example 1, respectively.
[Explanation of symbols]
1 Mixer
2 Extruder
3 Aquarium
4 Cutter
5 Liquefied carbon dioxide cylinder
6 Metering pump for carbon dioxide
7 Holding valve
8 Additive supply section
9 Thermoplastic resin (A)
10 Thermoplastic resin (B)
11 Hopper
12 Heater
13, 25, 26, 27, 28 Pressure gauge
14 Degassing mouth
15 die
16 pellets
17 Low molecular organic compound tank
18 Metering pump for low molecular organic compounds
19 Low molecular organic compound line
20 carbon dioxide line
21 First extruder
22 Second extruder
23 Third extruder
24 Refrigerant circulator
25 Mass flow meter

Claims (5)

In producing a thermoplastic resin composition by mixing two or more thermoplastic resins in an extruder in a molten state,
Using a multistage extruder with 3 or more extruders connected,
In a first extruder, carbon dioxide in a supercritical state is added in a ratio of 2 to 200 parts by weight with respect to 100 parts by weight of the total amount of the thermoplastic resin ,
Advance the fine dispersion of the molten mixture in the second extruder,
Carbon dioxide is degassed with a third extruder . A method for producing a thermoplastic resin composition. Further, in the first extruder, at least one carbon number of 1 selected from the group consisting of alcohols, alkanes, carboxylic acids, ethers, ketones and benzene is used with respect to 100 parts by weight of the total thermoplastic resin. The method for producing a thermoplastic resin composition according to claim 1, wherein the low molecular organic compound of ˜6 is added in a proportion of 0.01 to 50 parts by weight.   The method for producing a thermoplastic resin composition according to claim 2, wherein the low molecular organic compound is ethanol. A step of heating and melting and mixing two or more thermoplastic resins in the first extruder ;
Adding carbon dioxide to the molten mixture of two or more thermoplastic resins at a pressure of 3 to 50 MPa in a first extruder ;
A step of mixing two or more thermoplastic resins in a molten state in the second extruder in the presence of carbon dioxide;
The method for producing a thermoplastic resin composition according to any one of claims 1 to 3, further comprising a step of degassing carbon dioxide with a third extruder .   The method for producing a thermoplastic resin composition according to any one of claims 1 to 4, wherein the extruder is a single-screw extruder.

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