JP6426460B2 - Melt molding pellet mixture and molded article produced using the same - Google Patents

Description

  The present invention relates to a melt molding pellet mixture and a molded article produced using the same.

  Heretofore, in the field of polymer molded articles, a method containing a reinforcing agent such as carbon fiber or glass fiber has been used for molded articles from the viewpoint of improving the strength of the molded articles. From the viewpoint of securing interfacial adhesion, such molded articles are generally produced in advance using pellets formed by incorporating a reinforcing agent in a polymer (for example, Patent Document 1). .

JP, 2007-276274, A

  However, when a molded article is manufactured using one type of pellet in which two types of reinforcing agents are contained in a polymer, there arises a problem that a sufficiently good strength can not be obtained.

  An object of the present invention is to provide a melt-molding pellet mixture capable of producing a molded article having sufficiently good strength and a molded article produced using the same.

The present invention
A melt-forming pellet mixture comprising: a first pellet containing a first toughening agent and a first thermoplastic polymer; and a second pellet containing a second toughening agent and a second thermoplastic polymer,
When the first toughening agent and the second toughening agent have their respective elastic moduli E ₁ (GPa) and E ₂ (GPa), the following relational expressions are given:
E ₁ > E ₂
The filling,
Assuming that the melt viscosity of the first pellet and the second pellet is 8 ₁ (Pa · s) and η ₂ (Pa · s) at a shear rate of 8270 / s and a temperature of 230 ° C., the following relational expression:
η ₁ < _{2 2}
The present invention relates to a melt-forming pellet mixture satisfying the above, and a molded article obtained by melt-forming using the melt-forming pellet mixture.

  By using the melt molding pellet mixture according to the present invention, molded articles having sufficiently good strength can be produced.

It is a side view which shows the injection molding machine which attached the resin viscosity measuring apparatus for measuring the melt viscosity of a pellet in this invention with a partial cross section. It is a schematic plan view which shows the concrete structure of the joint surface with the fixed type in the movable type comprised to the resin viscosity measuring apparatus of FIG. (A) is an explanatory view of viscosity calculation, (B) is an explanatory view (pressure waveform diagram) of flow rate calculation. It is sectional drawing which shows an example of the injection molding machine for manufacturing a molded article using the pellet mixture of this invention. It is a side view which expands and shows the supply part of the screw of the injection molding machine of FIG. It is sectional drawing which expands and shows the backflow prevention ring part of the injection molding machine of FIG. It is a schematic block diagram of an example of the pellet manufacturing apparatus used by this invention.

  In the present invention, in a pellet mixture containing at least two types of reinforcing agents having different elastic moduli, the melt viscosity of the pellet containing the reinforcing agent having a relatively high elastic modulus under a specific condition is reinforced with a relatively low elastic modulus. Lower than the melt viscosity at the same conditions of the pellet containing the agent. Thereby, a molded article having sufficiently good strength can be manufactured. In the present invention, the details of the mechanism by which the strength of the molded article becomes sufficiently good is not clear, but is considered to be based on the following mechanism. The first pellet with low melt viscosity under shear flow at the time of molding tends to flow at the time of melt molding than the second pellet with high melt viscosity under the same conditions. Since such first pellets flow with the high modulus first toughening agent contained therein, the first toughening agent may be combined with the second toughening agent contained in the second pellet. It is well dispersed without intertwining. For example, in the case of producing a molded article by melt molding in which a molding direction (for example, injection direction, extrusion direction) such as injection molding, extrusion molding, etc. is defined, the molding direction and the molding direction The first reinforcing agent is well dispersed in any of the vertical directions (for example, the width direction and the thickness direction). As a result, in the present invention, it is considered that the strength of the molded article becomes sufficiently good.

  For example, when one type of pellet contains a reinforcing agent having a relatively high elastic modulus and a reinforcing agent having a relatively low elastic modulus, the strength of the resulting molded article is reduced. The reinforcing agents having different elastic moduli contained in the one kind of pellet are usually made of different materials, and are easily entangled in melt molding. The toughening agents of different materials come to have a slight opposite electrostatic charge electrostatically upon contact. For this reason, it is considered that the reinforcing agents of different materials are electrostatically attracted to each other, the dispersibility is lowered, and as a result, the strength is lowered. In particular, in the melt-forming method in which the forming direction is defined, it is considered that the strength is lowered because the dispersibility in the forming direction with respect to the entire reinforcing agent is reduced.

  Also, for example, even when using two kinds of pellets of a pellet containing a reinforcing agent having a relatively high elastic modulus and a pellet containing a reinforcing agent having a relatively low elastic modulus, the melt viscosity of the former pellet is the latter When the melt viscosity of the pellet is higher than that of the pellet, the strength of the resulting molded article decreases. A reinforcing agent having a relatively high elastic modulus contributes a relatively large amount to the improvement of the strength of the molded product, but since the pellet containing the reinforcing agent is hard to flow, the dispersibility of the reinforcing agent decreases. As a result, the strength of the molded article is considered to be reduced. In particular, in the melt-molding method in which the molding direction is specified, it is considered that the strength is lowered because the dispersibility in the molding direction with respect to the reinforcing agent having a relatively high elastic modulus is reduced.

[Pellet mixture]
The pellet mixture of the present invention is a mixture obtained by dry blending at least a first pellet and a second pellet.

The first pellet contains a first toughening agent and a first thermoplastic polymer.
The second pellet contains a second toughening agent and a second thermoplastic polymer.

The first reinforcing agent and the second reinforcing agent have the following relations, where E ₁ (GPa) and E ₂ (GPa) are elastic moduli:
E ₁ > E ₂
Meet.

Preferably, the first reinforcing agent and the second reinforcing agent have the following relation in view of further improvement of molded article strength:
30 ≦ E ₁ −E ₂ ≦ 1200
And more preferably the following relationship:
100 ≦ E ₁ −E ₂ ≦ 1200
Meet.

In the present specification, the elastic modulus of a reinforcing agent means a tensile elastic modulus, and the value measured by JIS R7606 or L1013 is used. However, when the reinforcing agent is talc, which is described later, the elastic modulus of talc is largely different depending on the place of production and the like, and it is difficult to measure alone, so the elastic modulus uses a value calculated by the following method. For example, the results of obtaining the elastic modulus _{E s} of samples of polypropylene 60% by weight, and talc 40 _weight%, and it E s = 4 GPa. At this time, the measurement of the elastic modulus is performed based on JIS K7113, and the sample is manufactured to a predetermined size by the method defined in JIS K7152. When the blending amount of talc in this sample is converted to “volume%” unit, it is 17.91 volume%. Since the modulus of elasticity of polypropylene is about 1 GPa, the modulus of elasticity E _{t of} talc can be obtained from the following formula of the composite law.
4 = E _t × 0.1791 + 1 × (1−0.1791)
E _t = 21.3

Elastic modulus _{E 1} of the first reinforcement is typically a 50～1500GPa, preferably from the viewpoint of further improvement of a molded article strength 200～1000GPa, more preferably 230～300GPa.
The elastic modulus _{E 2} of the second reinforcing agents usually from 10～250GPa, preferably from the viewpoint of further improvement of a molded article strength 15～100GPa, more preferably 50～100GPa.

  The first reinforcing agent and the second reinforcing agent are each independently selected from the group consisting of carbon fiber, glass fiber, and talc, as long as the above-described elastic modulus relationship formula is satisfied.

  Carbon fiber is a fiber produced by carbonizing at a high temperature a by-product such as petroleum, coal, coal tar (pitch) or polyacrylonitrile (PAN), and based on the material, pitch-based carbon fiber and PAN type carbon fiber is mentioned. The average fiber diameter of the carbon fiber is usually 7 to 10 μm, regardless of whether the carbon fiber is used as the first reinforcing agent or the second reinforcing agent. Carbon fibers are usually contained in the pellets at an average fiber length of 0.5 to 25 mm, preferably 6 to 13 mm.

Carbon fibers are commercially available.
Examples of pitch-based carbon fiber products include Dielead K13C6U (elastic modulus 900 GPa) manufactured by Mitsubishi Plastics, XN-60-60S (elastic modulus 620 GPa) manufactured by Japan Graphite Fiber Co., and the like.
Examples of PAN-based carbon fiber products include Toraya Toreca T700 (elastic modulus 230 GPa), Mitsubishi Rayon Pyrofil TR-50 S (elastic modulus 240 GPa), Toho Tenax HTA 40 (elastic modulus 240 GPa), and the like.

  Even when glass fibers are used as either the first reinforcing agent or the second reinforcing agent, the average fiber diameter of the glass fibers is usually 5 to 30 μm, preferably 10 to 24 μm. Glass fibers are usually contained in pellets at an average fiber length of 0.5 to 25 mm, preferably 6 to 13 mm.

Glass fibers are also commercially available.
Examples of glass fiber products include RS240 (elastic modulus 75 GPa) manufactured by Nittobo, ERS 2310 (elastic modulus 72.6 GPa) manufactured by Central Glass Fibers, and the like.

  Talc is a leaf-shaped or rod-shaped inorganic substance. When talc is used as a first toughening agent or a second toughening agent, the average particle size of talc is usually 0.2 to 10 μm, preferably 1 to 3 μm. The average particle diameter of talc is a value measured by a conventional method such as a laser diffraction method.

Talc is also commercially available.
Examples of products of talc include High Micron HE5 (average particle diameter: 1.6 μm) manufactured by Takehara Chemical Co., Ltd., Nano Ace D-1000 manufactured by Nippon Talc (average particle diameter: 1.0 μm), and the like.

The combination of the first toughening agent and the second toughening agent may be any combination as long as the above-described elastic modulus relationship formula is satisfied, for example, it may be a combination of different materials, or a combination of similar materials It may be Specific examples of the combination of the first toughening agent and the second toughening agent include, for example, the following combinations:
(R1) Carbon fiber (first reinforcing agent) -glass fiber (second reinforcing agent);
(R2) carbon fiber (first reinforcing agent) -talc (second reinforcing agent);
(R3) glass fiber (first reinforcing agent) -talc (second reinforcing agent);
(R4) pitch-based carbon fiber (first reinforcing agent) -PAN-based carbon fiber (second reinforcing agent).

  A preferred combination of the first toughening agent and the second toughening agent is the combination (R1) described above.

The content of the first strengthening agent is usually 5 to 40% by weight, preferably 10 to 30% by weight, based on the total weight of the first pellet.
The content of the second toughening agent is usually 5 to 70% by weight, preferably 20 to 60% by weight, based on the total amount of the second pellets.

  The present invention does not prevent that the first pellet contains two or more types of the first reinforcement and that the second pellet contains two or more types of the second reinforcement as long as the effects of the present invention can be obtained. However, the first pellet usually contains only one type of strengthening agent as the first strengthening agent, and the second pellet usually contains only one type of strengthening agent as the second strengthening agent. When the first pellet contains two or more types of first strengthening agents, the total content thereof may be in the above range. When a 2nd pellet contains 2 or more types of 2nd strengthening agents, those total content should just be in the said range.

In the present invention, when the first pellet and the second pellet have respective melt viscosity η ₁ (Pa · s) and η ₂ (Pa · s), the following relational expressions are given:
η ₁ < _{2 2}
Meet. If the relationship is not satisfied, as described above, the melt viscosity of the first pellet containing a reinforcing agent having a relatively high modulus of elasticity is higher than the melt viscosity of the second pellet containing a reinforcing agent having a relatively low modulus of elasticity. Also, the strength of the molded article decreases.

Preferably, the first pellet and the second pellet have the following relationship from the viewpoint of further improving the molded article strength:
1.1 ≦ η ₂ / η ₁ ≦ 10
And more preferably the following relationship:
1.2 ≦ η ₂ / η ₁ ≦ 10
And more preferably the following relationship:
1.2 ≦ η ₂ / η ₁ ≦ 3
Meet.

  In the present specification, the melt viscosity means a viscosity at a shear rate of 8270 / s and a temperature of 230 ° C., and a value measured by a measuring device and a measuring method described later is used.

Melt viscosity (eta) ₁ of a 1st pellet is 10-40 Pa * s normally, Preferably it is 15-25.
The melt viscosity η ₂ of the second pellet is usually 15 to 50 Pa · s, preferably 20 to 30.

The melt viscosity can be controlled by adjusting the type, content and fiber length of the reinforcing agent, type and molecular weight of the thermoplastic polymer, and the like.
For example, when a polymer having a large MFR value at a predetermined temperature is used as the thermoplastic polymer, the melt viscosity of the composite is lower.

  According to the present invention, as long as the effects of the present invention can be obtained, the first pellet contains other strengthening agents in addition to the first strengthening agent, and the second pellet contains other strengthening agents in addition to the second strengthening agent. Although not disturbing, the first pellet usually contains only the first strengthening agent as a strengthening agent, and the second pellet usually contains only the second strengthening agent as a strengthening agent.

  The first thermoplastic polymer and the second thermoplastic polymer are each independently selected from the group consisting of polyolefins, polyesters, polyurethanes, polyamides, etc., but the first thermoplastic polymer and the second thermoplastic polymer are compatible. It is selected from the combination of what it has.

  Examples of the polyolefin include polyethylene, polypropylene and ethylene / propylene copolymer.

The melt flow rate M1 of the _first thermoplastic polymer is usually 40 to 200 g / 10 min, preferably 65 to 100 g / 10 min.
The melt flow rate M2 of the _second thermoplastic polymer is usually 3 to 50 g / 10 min, preferably 5 to 30 g / 10 min.

  In the present specification, as the melt flow rate of the thermoplastic polymer, the value measured by JIS K7210 is used. The measurement conditions when the polymer is PP are 230 ° C. and 0.45 MPa.

  The present invention prevents that the first pellet contains two or more first thermoplastic polymers and the second pellet contains two or more second thermoplastic polymers as long as the effects of the present invention can be obtained. Although not preferred, the first pellet usually contains only one thermoplastic polymer as the first thermoplastic polymer, and the second pellet usually contains only one thermoplastic polymer as the second thermoplastic polymer. It is When the first pellet contains two or more types of first thermoplastic polymers, the melt viscosity of the first pellet containing the mixture thereof may satisfy the above-described relationship with the melt viscosity of the second pellet. When the second pellet contains two or more types of second thermoplastic polymers, the melt viscosity of the second pellet containing the mixture thereof may satisfy the above-mentioned relationship with the melt viscosity of the first pellet.

Examples of combinations of the first thermoplastic polymer and the second thermoplastic polymer include the following combinations:
(P1) polyolefin-polyolefin;
(P2) polyester-polyester;
(P3) thermoplastic polyurethane-thermoplastic polyurethane;
(P4) polyethylene-polyethylene;
(P5) polypropylene-polypropylene;
(P6) polyethylene-polypropylene;
(P7) polyethylene-ethylene-propylene copolymer;
(P8) polypropylene-ethylene / propylene copolymer.

  A preferred combination of the first thermoplastic polymer and the second thermoplastic polymer is the combination (P1) described above, in particular the combination (P5).

  The first pellet may contain other additives in addition to the first toughening agent and the first thermoplastic polymer as long as the effects of the present invention can be obtained. Other additives include, for example, antioxidants, ultraviolet light absorbers, and the like. The content of other additives in the first pellet is usually 1% by weight or less based on the first thermoplastic polymer.

  The second pellet may also contain other additives in addition to the second toughening agent and the second thermoplastic polymer as long as the effects of the present invention can be obtained. Other additives are similar to other additives that may be contained in the first pellet. The content of other additives in the second pellet is usually 1% by weight or less based on the second thermoplastic polymer.

  The first pellet and the second pellet can be produced by a known pelletizing method. For example, it can be manufactured by melting and kneading a predetermined toughening agent and a thermoplastic polymer, extruding, cooling the extruded kneaded material, and cutting with a cutting machine such as a rotary blade. Alternatively, it can be produced by drawing, cooling, and cutting while impregnating a molten polymer around a reinforcing agent, as in the case of a wire coating.

  The shape of the first pellet and the second pellet is not particularly limited, and may be, independently, for example, a cylindrical shape, an elliptic cylindrical shape, or the like.

  The length (maximum length) per particle of the first pellet and the second pellet is usually independently 3 to 25 mm, preferably 6 to 12 mm.

  The mixing ratio of the first pellet to the second pellet is not particularly limited, but is usually 1/9 to 9/1 by weight, and preferably 2/8 to 6/4.

  The pellet mixture of the present invention may contain other pellets in addition to the first pellet and the second pellet. Other pellets include pellets of a thermoplastic polymer (so-called color masterbatch) containing a high concentration of pigment for coloring. The content of other pellets is usually at most 3% by weight based on the total weight of the pellet mixture.

[Measuring apparatus and measuring method of melt viscosity]
First, the measuring apparatus will be described in detail.
The melt viscosity of the pellet is measured by a resin viscosity measuring device 50, and the resin viscosity measuring device 50 is used by being connected to an injection molding machine 10 as shown in FIG. The injection molding machine 10 shown in FIG. 1 is an in-line screw type, in which 1 is a heating cylinder, 2 is a hopper for supplying pellets (pellet-like resin material) to the heating cylinder 1, and 3 is a built-in injection cylinder. 4 is a fixed board, 5 is a movable board. The heating cylinder 1 is for melting and plasticizing and transporting a resin material, and a band heater (not shown) is attached to the outer periphery, and a screw 8 is provided inside. The resin material is heated and plasticized by heat transfer from the outside and shear force by rotation of the screw 8. A backflow prevention valve 9 is provided at the tip of the screw 8, and the molten resin is injected from the injection nozzle 7 at the tip of the heating cylinder 1 into the cavity of the molding die as the screw 8 advances.

  At the time of melt viscosity measurement, as shown in FIG. 1, the resin viscosity measurement device 50 is attached to the injection molding machine 10. In the resin viscosity measurement device 50, the measurement fixed die 20 is attached to the fixed plate 4 and the measurement movable die 30 is attached to the movable plate 5.

FIG. 2 shows the specific structure of the mating surface (molding surface) 31 of the movable die 30 with the fixed die 20. As shown in FIG. A channel (groove) 32 is formed in a substantially spiral shape on the molding surface 31 of the movable mold 30, and the inlet 33 at one end of the channel 32 is connected to the sprue 21 formed in the fixed mold 20, The outlet 34 at the other end of the passage 32 is open below the movable mold 30. Therefore, the molten resin flowing from the sprue 21 into the flow path 32 through the inflow port 33 flows in the flow path 32 toward the outflow port 34 at a high shear rate. The inflow port 33 is not formed as a hole at one end of the flow channel 32, but is an inlet that allows molten resin to flow into the flow channel 32 through communication with the sprue 21 of the fixed mold 20.
The mating surface (molding surface) of the fixed die 20 with the movable die 30 is a flat surface.

  In the flow path 32 of the movable die 30, pressure sensors 35a and 35b for detecting a pressure gradient of the molten resin flowing through the flow path 32 are provided at two places at intervals in the flow direction. The temperature of the molten resin is measured by a temperature sensor (not shown) disposed at the injection nozzle 7 of the injection molding machine 10 shown in FIG.

Next, the measurement method will be described in detail.
The fixed mold 20 and the movable mold 30 of the resin viscosity measuring device 50 are attached to the injection molding machine 10 by the fixed board 4 and the movable board 5. The injection nozzle 7 of the injection molding machine 10 is advanced to be connected to the sprue 21 (nozzle touch).

  The screw 8 is rotated and retracted while the heating cylinder 1 is heated to a predetermined temperature. As a result, the resin material supplied from the hopper 2 is heated and plasticized, and the molten resin is accumulated at the tip of the heating cylinder 1 (metering). By advancing the screw 8, the measured molten resin at the tip of the heating cylinder 1 flows from the injection nozzle 7 through the sprue 21 into the flow path 32 between the fixed mold 20 and the movable mold 30, and flows Evacuate the outlet 34. The pressure gradient ∂P / ∂x of the molten resin flowing in the flow path 32 at this time is obtained from the detection values of the pressure sensors 35a and 35b. Further, the flow rate Q of the molten resin flowing through the flow path 32 is separately obtained. Based on the pressure gradient ∂P / ∂x and the flow rate Q, the viscosity η of the molten resin at the temperature T is determined.

That is, in FIG. 3 (A), the height of H is the channel 32 (depth), _{P 1} and _{P 2} is the detection value of the pressure sensor 35a, 35b. The viscosity η can be expressed by the following equation (1), where the shear rate is γ and the shear stress is τ _W. Further, assuming that the width of the flow channel 32 is W, the shear rate γ can be expressed by the following equation (2), and the shear stress τ _W can be expressed by the following equation (3).

  Since H and W are the height and width of the resin flow path 32, when the pressure gradient ∂P / ∂x and the flow rate Q are obtained, the viscosity η at the temperature T can be obtained. The resin temperature T can be given, for example, by a detection value of a temperature sensor (not shown) disposed at the injection nozzle 7 of the injection molding machine 10 shown in FIG. After the viscosity measurement, the fixed mold 20 and the movable mold 30 can be opened to remove the solidified resin in the flow path 32.

  Next, how to find the flow rate Q will be described. FIG. 3 (B) is an explanatory view for that. The molten resin is injected into the flow path 32 at least twice by changing the injection amount of the molten resin under the same conditions (heat plasticization conditions, injection speed (screw advancing speed)) as the pressure gradient is determined.

FIG. 3B schematically shows the pressure waveform of the molten resin detected by the pressure sensor 35a when injection is performed with different actual injection amounts (Q1 and Q2). The actual injection amounts Q1 and Q2 can be obtained from the outflow amount of the molten resin from the flow passage 32 and the remaining amount of the molten resin in the flow passage 32. Based on these pressure waveforms, the end points t ₁ and t ₂ of the stable flow period of the molten resin in each of the actual injection amounts Q 1 and Q ₂ are specified, and the difference Δt = t ₂ −t ₁ is determined. This Δt corresponds to the change amount of the stable flow period accompanying the change of the actual injection amount from Q1 to Q2. Next, the difference ΔQ (= Q2-Q1) of the actual injection amounts Q1 and Q2 is determined. Therefore, the flow rate Q of the stable flow period of the molten resin in the flow path 32 can be obtained by dividing ΔQ by Δt (Q = ΔQ / Δt).

  In the present invention, the melt viscosity η is measured when the shear rate γ is 8270 / s and the temperature T is 230 ° C. in the above-described measurement apparatus and measurement method.

In the present invention, since the melt viscosity of the pellet is measured by the above method, it has the following advantages:
(1) The pellet can be defined by the melt viscosity which closely approximates the actual melt viscosity at the time of molding.
(2) It is possible to measure not the melt viscosity of the polymer but the melt viscosity as a composite material containing a reinforcing agent.

[Molding]
A molded article can be produced by subjecting the pellet mixture of the present invention to a melt molding method. The melt-forming method is a method of plasticizing and melting a pellet, forming it, and then solidifying it by cooling. As such a melt molding method, an injection molding method, an extrusion molding method, a press molding method etc. are mentioned, for example. Among the melt molding methods, it is preferable to manufacture molded products by employing an injection molding method capable of molding a complicated shape with high productivity, an extrusion molding method capable of continuously molding a long shape, or the like. More preferably, an injection molding method is employed.

  When employing the injection molding method, an example of a low shear type injection molding machine suitable for injection molding using the pellet mixture of the present invention is shown in FIG.

  In the injection molding machine shown in FIG. 4, reference numeral 101 denotes a heating cylinder, and reference numeral 102 denotes a low shear type screw rotatably and retractably disposed in the heating cylinder 101. Although not shown, the injection molding machine includes a motor that rotationally drives the screw 102 and an injection cylinder that drives the screw 102 back and forth. Further, the screw head portion is not provided with a mixing head for enhancing the dispersibility of the pigment and the like.

  A hopper 103 for charging the molding material is provided on the base end side of the heating cylinder 101, and an injection nozzle 104 is provided on the tip of the heating cylinder 101. A band heater as an external heater 105 is wound around the outer periphery of the heating cylinder 101. The injection nozzle 104 is connected to a runner 107 of a mold 106 for molding a fiber reinforced resin molded product. The mold 106 is constituted by a fixed mold 106 a having a runner 107 and a movable mold 106 b. A cavity 108 is formed by the fixed mold 106a and the movable mold 106b.

  The screw 102 includes a screw main body 111 and a screw head 112 coupled to the tip of the screw main body 111. The screw main body 111 is a single flight type in which the flight 113 is formed in one strip. The ratio L / D of the length L of the screw main body 111 (the length from the material supply port 113 to the tip of the screw) L and the diameter D of the screw main body 111 is preferably 22 or more. The upper limit of the L / D ratio may be, for example, about 30.

  The screw main body 111 includes a supply unit 114, a compression unit 115, and a measurement unit 116 in order from the base end side (upstream side) to the tip end side (downstream side). The feeding portion 114 has a length of 10 times or more and 15 times or less of the diameter D. As shown in FIG. 5, the screw groove depth (height of the flight 113) d of the supply portion 114 is constant over the entire length of the supply portion 114, and the groove depth d is greater than any pellet length of the molding material 117. large. The molding material 117 supplied from the hopper 103 to the supply unit 114 is sent toward the compression unit 115 in the space divided by the flight 113 by the rotation of the screw 102 while being softened by the heat of the external heater 105. .

  The compression section 115 is a section in which the screw groove depth gradually decreases. The molding material 117 is compressed by the rotation of the screw 102 in the compression unit 115, plasticized and melted under large shear force and heat, and sent to the measurement unit 116 as a molten resin. The measuring unit 116 has a constant screw groove depth over the entire length of the measuring unit 116 and is equal to the minimum screw groove depth of the compressing unit 115 so that the molten resin is stored in the resin reservoir in front of the screw 102. It is formed of

  The compression ratio of the screw 102 (the ratio of the volume per pitch of the grooves of the supply portion 114 and the metering portion 116) is usually 1.6 or more and 1.8 or less.

  As shown in FIG. 6, the back of the screw head 112 is provided with a backflow prevention ring 118 having a corotating structure. The backflow prevention ring 118 is fitted to a connecting shaft 119 connecting the screw main body 111 and the screw head 112 so as to be able to move forward and backward with a gap 120 serving as a flow path of the molten resin. On the outer periphery of the proximal end portion of the screw head 112, grooves 121 opened in the proximal end surface of the head 112 are formed at intervals in the circumferential direction, and projections 122 protruding forward from the backflow prevention ring 118 are formed in the grooves 121. Is engaged. This engagement causes the non-return ring 118 to rotate with the screw 102.

(Pellets A)
The pellet was manufactured using the pellet manufacturing apparatus shown in FIG. Specifically, using a twin-screw extruder (manufactured by Plastic Engineering Laboratory, screw diameter: 30 mm) 200, the following materials were melted, kneaded and extruded under the following conditions. After the extruded kneaded material was cooled by a water bath 201, it was cut by a rotary blade of a pelletizer 202 to obtain pellets A (cylindrical shape) having an average length of 4 mm per particle.
material:
Polypropylene, manufactured by Japan Polypropylene Corporation, MFR 75 g / 10 min, 80% by weight, and PAN-based carbon fiber, manufactured by Toray Industries, elastic modulus 230 GPa, 20% by weight.
conditions:
Set temperature of heating cylinder: 230 ° C;
Extruded amount: 8 kg / hour;
Screw rotational speed: 180 rpm.

(Pellets B)
Pellets B were obtained in the same manner as the pellets A, except that the following materials were melted and kneaded.
material:
Polypropylene, manufactured by Japan Polypropylene Corporation, MFR 75/10 minutes, 80% by weight, and Glass fiber, manufactured by NITTOBO CO., LTD., Elastic modulus 75 GPa, 20% by weight.

(Pellets C)
Pellets C were obtained in the same manner as the pellets A, except that the following materials were melted and kneaded.
material:
Polypropylene, manufactured by Japan Polypropylene Corporation, MFR 21 g / 10 min, 80% by weight, and Glass fiber, manufactured by Nittobo, elastic modulus 75 GPa, 20% by weight.

(Pellets D)
Pellets D were obtained in the same manner as the pellets A, except that the following materials were melted and kneaded.
material:
Polypropylene, manufactured by Japan Polypropylene Corporation, MFR 11 g / 10 min, 80% by weight, and Glass fiber, manufactured by Nittobo, elastic modulus 75 GPa, 20% by weight.

(Pellets E)
Pellets E were obtained in the same manner as the pellets A, except that the following materials were simultaneously melted and kneaded.
material:
・ Polypropylene, made by Japan Polypropylene, MFR 75g / 10 min, 40% by weight
・ Polypropylene, made by Japan Polypropylene, MFR 11 g / 10 min, 40% by weight
PAN-based carbon fiber, manufactured by Toray Industries, Inc., elastic modulus 230 GPa, 10% by weight, and glass fiber, manufactured by Nittobo, elastic modulus 75 GPa, 10% by weight.

(Melt viscosity of pellet)
The melt viscosity of the pellets was measured using the above-described measuring apparatus and measuring method. The more detailed measurement conditions were as follows.
Shear rate γ: 8270 / s;
Cross-sectional shape of the flow path 32 (FIG. 2): Width W of the flow path 32 (FIG. 2): 20 mm
Height H of the flow path 32 (FIG. 2): 2 mm
Internal temperature T of heating cylinder 1 (Fig. 1): 230 ° C
Rotation speed of screw 8 (Fig. 1): 60 rpm
Mold set temperature: 40 ° C
Positions of pressure sensors 35a and 35b: positions of 80 mm and 110 mm from the end of the inlet 33, respectively.

(Example and Comparative Example)
The pellets shown in the table were dry blended to obtain a pellet mixture. The obtained pellet mixture is applied to an injection molding machine shown in FIGS. 4 to 6, and injection molding is performed under the following conditions to obtain a flat molded article (MD direction length 180 mm × TD direction length 180 mm × thickness 3 mm) Obtained. The MD direction is the flow direction, and the TD direction is the direction perpendicular to the MD direction on the flat surface.

Injection molding conditions:
Equipment: Made in Japan Steel Works;
Clamping force: 220 tons electric motor;
Back pressure: 3 MPa;
Cylinder set temperature: 230 ° C;
Screw type: low shear type (single flight type, no mixing head);
Screw rotational speed: 60 rpm;
Injection pressure: 250MPa;
Injection speed: 50 mm / sec;
Holding pressure: 25 MPa;
Holding time: 8 seconds;
Mold set temperature: 40 ° C.

(Evaluation)
The obtained flat plate was cut to prepare a sample of 80 mm × 10 mm × 3 mm in size. The sample includes five samples MD positioned such that the long axis direction is parallel to the MD direction, and five samples TD positioned such that the long axis direction is parallel to the TD direction.
The flexural modulus of the sample was measured in accordance with JIS K7171. The table shows the mean value for sample MD and the mean value for sample TD.

The molded article obtained in the example had a sufficiently higher elastic modulus than the molded article obtained in the comparative example. In particular, the sample MD of the molded article obtained in the example had a significantly superior modulus of elasticity than the sample MD of the molded article obtained in the comparative example.
From these results, it is considered that the molded article obtained using the pellet mixture of the present invention is superior to the conventional molded article in the dispersibility of the reinforcing agent. Molded articles obtained using the pellet mixture of the present invention are considered to be excellent in the dispersibility of the reinforcing agent particularly in the MD direction as compared to conventional molded articles.

  The pellet mixture of the present invention is useful as a material for manufacturing structural parts such as door module carriers and lift gate inners in the automotive field.

1: heating cylinder 2: hopper 3: injection device 4: fixed plate 5: movable plate 10: injection molding machine 20: fixed type 30: movable type 50: resin viscosity measuring device 102: low shear type screw 113: flight 118: common Rotating structure backflow prevention ring

Claims (8)

A melt-forming pellet mixture comprising: a first pellet containing a first toughening agent and a first thermoplastic polymer; and a second pellet containing a second toughening agent and a second thermoplastic polymer,
When the first toughening agent and the second toughening agent have their respective elastic moduli E ₁ (GPa) and E ₂ (GPa), the following relational expressions are given:
E ₁ > E ₂
The filling,
Assuming that the melt viscosity of the first pellet and the second pellet is η ₁ (Pa · s) and η ₂ (Pa · s) at a shear rate of 8270 / s and a temperature of 230 ° C., respectively:
η ₁ < _{2 2}
Meet the,
The first reinforcing agent is carbon fiber,
The second reinforcing agent is glass fiber,
The combination of the first thermoplastic polymer and the second thermoplastic polymer is the following combination:
(P1) polyolefin-polyolefin;
(P2) polyester-polyester;
(P3) thermoplastic polyurethane-thermoplastic polyurethane;
(P4) polyethylene-polyethylene;
(P5) polypropylene-polypropylene;
(P6) polyethylene-polypropylene;
(P7) polyethylene-ethylene-propylene copolymer;
(P8) polypropylene-ethylene / propylene copolymer,
Melt forming pellet mixture selected from the group consisting of The first and second pellets have the following relationship:
1.1 ≦ η ₂ / η ₁ ≦ 10
The filling,
The first strengthening agent and the second strengthening agent have the following relationship:
30 ≦ E ₁ −E ₂ ≦ 1200
The melt molding pellet mixture according to claim 1, wherein The melt viscosity η ₁ of the first pellet is ₁₀ to 40 Pa · s,
The melt viscosity η ₂ of the second pellet is 15 to 50 Pa · s,
The elastic modulus E ₁ of the first reinforcing agent is 50 to 1,500 GPa,
Melt molding pellets mixture according to claim 1 or 2 elastic modulus _{E 2} of the second reinforcing agent is 10～250GPa. The first pellet contains 5 to 40% by weight of the first strengthening agent,
The melt-forming pellet mixture according to any one of claims 1 to 3 , wherein the second pellet contains 5 to 70% by weight of the second strengthening agent. The first thermoplastic polymer is polypropylene,
The melt-forming pellet mixture according to any one of claims 1 to 4 , wherein the second thermoplastic polymer is polypropylene.   The combination of the first thermoplastic polymer and the second thermoplastic polymer is the following combination:
  Polyester-polyester;
  Thermoplastic polyurethane-Thermoplastic polyurethane;
  Polyethylene-polyethylene; and
  Polypropylene-polypropylene,
The melt-forming pellet mixture according to any one of claims 1 to 4, which is selected from the group consisting of The pellet mixture for melt molding according to any one of claims 1 to 6 , wherein the melt molding is injection molding. A molded article produced using the melt molding pellet mixture according to any one of claims 1 to 7 .

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