JP2000141452A - Extruder of polypropylene resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an extruder for efficiently producing a polypropylene compsn. reduced in fish eye containing an elastomer component comprising an α-olefin copolymer of a different kind without damaging productivity and quality. SOLUTION: An extruder mainly consists of the melting part provided on this side of a kneading part to perfectly melt a resin and the kneading part having a kneading element capable of applying shearing strain to the molten resin uniformly and capable of setting an A-value, which is calculated according to A=η.Σ(S).n (wherein η is the shearing viscosity of the resin of the kneading part, S is the shearing strain quantity in the element part and n is the number of times of shearing strain applied to the resin by element flights) to 109 or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extruder for producing a polypropylene resin composition having less fish eyes. Fish eyes of a polypropylene resin composition containing an elastomer component are known as an inhibitory factor such as impact strength, appearance, and tensile elongation. By efficiently eliminating the fish eyes, polymerization costs can be suppressed, and a balance between productivity and quality, which cannot be achieved by a continuous process due to the generation of conventional fish eyes, can be achieved.

[0002]

2. Description of the Related Art Fish-eye of a polypropylene resin composition containing an elastomer component comprising a copolymer with a different α-olefin such as an ethylene-propylene copolymer has an impact strength, an appearance, a tensile elongation, and a coating. It has been conventionally known as an inhibitory factor for the properties and the like. In the continuous polymerization method, for controlling this fish eye, for example, Japanese Patent Application Laid-Open No. 58-49
No. 716, JP-A-61-69
No. 821, a method in which alcohols are used as polymerization deactivators. However, the polymerization activity has been dramatically improved due to the recent advances in catalyst development technology.As a result, the control of fish eyes was insufficient with a conventional classifier alone. From the perspective of productivity,
It was not a very effective tool. For this reason,
The development of an extruder capable of efficiently eliminating fish eyes in the melt-kneading and granulating process and the design technology thereof have been awaited.

[0003]

An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to efficiently produce a polypropylene resin composition containing an elastomer component without impairing productivity and quality. To provide an extruder.

[0004]

Means for Solving the Problems The present inventors have paid attention to the fact that fish eyes of a polypropylene resin composition containing an elastomer component can be eliminated by melt kneading, and have eagerly studied a method of eliminating fish eyes by melt kneading. As a result of the study, there is a good correlation between the shear viscosity of the molten resin during kneading, the physical quantity obtained by multiplying the total value of the shear strain given to the molten resin and the number of times of the given shear strain, and the fisheye elimination performance in the extruder. The inventors have found that the present invention has been completed.

That is, the present invention relates to an extruder for efficiently eliminating fish eyes of a polypropylene resin composition containing an elastomer component, wherein the extruder comprises a polypropylene resin containing an elastomer component composed of a heterogeneous α-olefin copolymer. An extruder for a system resin composition, mainly a melting section for completely melting the resin in front of the kneading section, and an element capable of uniformly imparting shear strain to the molten resin, And an extruder comprising a kneading section having a kneading element capable of setting an A value calculated by the following formula (1) to 10 ⁹ or more.

[0006]

Formula (1) A = η ·） (S) · n (1) (where η represents the shear viscosity of the resin in the kneading portion, S represents the amount of shear strain in each flight portion of the element, and n Represents the number of shear strains applied to the resin by element flight.)
It is the gist.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The target resin composition to which the extruder of the present invention is applied is a polypropylene-based resin composition containing an elastomer component obtained by copolymerization with a different α-olefin,
30 ° C. melt flow rate is 0.5 to 100 g / 10
min. and a polypropylene resin composition containing 5 to 60% by weight of an elastomer component. The molecular weight ratio of the included elastomer component and polypropylene component is Mw (elastomer) / Mw (polypropylene)
1 to 20, preferably 2 to 10. The polymerization of the resin composition is preferably continuous polymerization from the viewpoint of productivity, and the polymerization method can be any method such as slurry polymerization, bulk polymerization, and gas phase polymerization. Elastomer components contained are ethylene, propylene, 1-butene, 1
-A copolymer obtained by copolymerizing any α-olefin such as pentene, 1-hexene and styrene can be used, preferably ethylene, propylene and 1-butene, and more preferably a copolymer of ethylene and propylene. It is. In the polymerization of the polypropylene resin composition,
For example, by using a classifier shown in JP-A-58-49716 or a method using an alcohol as a polymerization deactivator shown in JP-A-61-69821, continuous production is performed within a range where productivity is not impaired. The generation of fish eyes generated by the polymerization method can be prevented.

[0008] The polypropylene resin powder thus polymerized is processed into a pellet-shaped resin product in a melt-kneading and granulating step. At this time, as long as the effects of the present invention are not significantly impaired, if necessary, And other optional components may be blended. Such other optional components include, for example, antioxidants, ultraviolet absorbers, light stabilizers, lubricants, antistatic agents, coloring agents, conductive agents, dispersants, printability-imparting agents, molecular weight regulators, cross-linking agents , A crosslinking aid, a filler, a flame retardant, a flame retardant aid, a foaming agent, a processing aid, a neutralizing agent, a heavy metal deactivator, a nucleating agent, an antifogging agent, and the like.

Next, the extruder of the present invention will be described with reference to the accompanying drawings. The extruder of the present invention is of a continuous type, and is capable of uniformly imparting a shear strain to a kneading element in which a short path is prevented, that is, all the elastomer particles. There is no particular limitation as long as the extruder has a kneading element capable of setting the A value determined by the product of the indicated shear viscosity, the total shear strain and the number of shear strains to 10 ⁹ or more.

Specifically, the extruder having the kneading element A shown in FIGS. 2 and 3 has excellent effects. FIG.
Is a side view of the kneading element A, and FIG.
FIG. 2 shows an X-ray sectional view. That is, it has a barrel and a series of longitudinal introduction grooves 5 mounted inside the barrel and closing and terminating in the outlet direction, and a series of longitudinal discharge grooves 7 closing and terminating in the entrance direction. A cylinder is provided with a flight tip portion 6 that forms a partition (flight) having a clearance between the discharge tip 7 and the inner wall of the barrel. Resin is introduced into the introduction groove 5 and the flight tip portion 6 is formed.
The element which passes through the discharge groove 7 and has a structure to be discharged and is provided with a uniform shear strain is effectively used. The clearance between the flight tip and the barrel inner wall is appropriately selected to provide the required shear rate applied to the resin.

The element having such a structure is connected to, for example, a screw of a commonly used single screw extruder, and is installed so as to rotate together with the screw. Using such an element, the design and setting are performed so that the value of the A value is 10 ⁹ or more. If the value of the A value is less than 10 ⁹ , fish eyes are not sufficiently eliminated in the extruder, and the effect of the present invention cannot be obtained. The calculation method of the A value is as shown in the calculation formula (1). More specifically, the calculation is performed by the following method.

[0012]

A = η · Σ (S) · n (1) η (poise): Shear viscosity of kneading part resin: calculated from the kneading part resin temperature and the shearing rate of the flight tip part. Σ (S): total amount of shear strain: total value of the amount of shear strain at each flight tip portion S = ν · t ν = (π · D · R) / (60h) t = w / q

Here, S: amount of shear strain at each flight tip portion ν: shear speed at the flight tip portion t: time for resin to pass through the flight tip portion D: element diameter (mm) R: screw rotation speed (rpm) H) Minimum distance between flight tip and cylinder inner wall (m
m) w: land width of flight chip (mm) q: flight speed of resin in flight chip (kg / h) π: pi n: number of shear strains = number of flight chips through which resin passes

The operating conditions of the extruder are not particularly limited, except that it is necessary to adjust the screw rotation speed and the extrusion rate or the resin temperature so that the A value becomes 10 ⁹ or more. The liquid is added and devolatilized using a cylinder cooling device on the outer periphery of the cylinder, a liquid addition nozzle provided in front of the kneading unit entrance and a deaerator located between the kneading unit outlet and the extrusion die, and the devolatilization It is possible to adjust the resin temperature. The extruder is preferably a one-stage extruder from the viewpoint of the productivity of the apparatus, but may be a two-stage extruder. The extruder is a single-screw or twin-screw extruder. When a twin-screw extruder is used, a partition plate or the like is used between the screw shafts so that a short path does not occur in the kneading portion. Therefore, it is necessary to keep the clearance constant. Further, by dividing the cylinder of the kneading section into two axes and making the cylinder and element shape of the kneading section conical, the clearance can be appropriately adjusted during operation. The screen mesh for making the fish eye finer is a fine mesh having an opening of # 200 mesh or more, preferably # 300 mesh or more, more preferably # 400 mesh or more. This screen mesh is installed in front of the extrusion die. However, it is preferable to provide a screen changer that can be replaced as desired during operation in order to maintain continuous productivity. Such a continuous extruder can greatly improve the removal performance of fish eyes, which could not be done conventionally, and therefore, the productivity is not high with conventional classification technology and polymerization technology represented by the use of alcohols. Quality can be controlled in the melt-kneading and granulating process without sacrificing productivity. Further, since the removal of fish eyes is performed after the resin is completely melted, the energy required for kneading can be saved, and from the viewpoint of energy efficiency, the industrial value thereof is extremely large in recent years when energy resources are scarce.

[0015]

EXAMPLES Hereinafter, the effects of the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto without departing from the gist of the present invention. In the present invention, the number of fish eyes used as a quality judgment scale was measured by the following method. The extruded and granulated polypropylene resin pellets were extruded with a T-die film forming machine equipped with a full flight screw having a diameter of 40 mm to form a film having a thickness of 30 μm, using a defect inspection device GX40 manufactured by Diamond Instruments, Inc. Adjust the scan cycle so that the accumulated signal voltage becomes 600 mV,
While passing the film at a film passing speed of 5 m / min, a diameter of 5 cm per 250 cm ² is observed.
The number of fish eyes of 0 micron or more was counted.

Example 1 FIG. 1 is a schematic view showing one embodiment of an extruder according to the present invention. As shown in FIG. 1, a single screw extruder 2 having a full flight screw having a diameter of 65 mm, and a single screw extruder 3 capable of mounting a kneading element having a diameter of 54 mm as a segment.
Are arranged in series, and the resin powder is completely melted by heating the cylinder in the first-stage single-screw extruder 2, and the short path shown in FIGS. The kneading element A, which does not cause the waking, was mounted, and a kneading experiment was performed. In the experiment, a polypropylene-based resin composition (1) containing 15% by weight of an elastomer component obtained by copolymerizing ethylene and propylene was used. In the first stage extruder, the screw was rotated at 60 rpm, the cylinder temperature was heated to 170 ° C. by an electric heater, and the resin was melted and extruded while the hopper 1 was filled with the resin powder. The extruded molten resin is supplied to the second-stage extruder through a pipe connecting both extruders, and the extrusion rate is 30 kg / h from a die provided at the outlet of the second-stage extruder.
Extruded with. The second-stage extruder uses a cylinder through which cooling water can flow, and is operated by an electric heater and cooling water.
The temperature of the cylinder was adjusted to 5 ° C. The test was performed at a screw rotation speed of 600 rpm. In this experiment, the A value, the operating conditions of the extruder, and the measured values of fish eyes of the obtained pellets were as shown in Table 1.

Example 2 In the polymerization of a polypropylene resin, the amount of the polymerization deactivator used was changed to further increase the polymerization activity, and the polymerization was carried out. A polypropylene resin composition containing 15% by weight of an elastomer component ( An experiment was conducted in the same manner as in Example 1 except that kneading element B shown in FIG. 4 was used, and the results shown in Table 1 were obtained.

Comparative Example 1 An experiment was conducted in the same manner as in Example 1 except that the screw rotation speed of the second-stage extruder was set to 200 rpm.
The results shown in Table 1 were obtained. Comparative Example 2 An experiment was performed in the same manner as in Example 2 except that the screw rotation speed of the second-stage extruder was set to 200 rpm.
The results shown in Table 1 were obtained.

Comparative Example 3 As shown in FIG. 5, a screw configuration having a short path and having a screw configuration, a co-axial twin-screw extruder CMP65X manufactured by Nippon Steel Works (kneading part specification: 0.5D width KD, shifted 30 ° in the forward direction, number of disks 12) and screw rotation speed 400rpm
m, extrusion rate 300 kg / h, cylinder adiabatic operation,
The polypropylene resin composition (1) used in Example 1 was extruded. The results obtained are as shown in Table 1. Comparative Example 4 An experiment was conducted in the same manner as in Comparative Example 3 except that the cylinder was cooled with a cooling water and an electric heater, and the kneading section cylinder temperature was set to 120 ° C., and the results shown in Table 1 were obtained.

Comparative Example 5 In order to lower the resin temperature in the kneading section, water was injected from a liquid addition nozzle provided in front of the kneading section, and the water injected from a devolatilization port provided in the discharge section was recovered as steam. Except for this, an experiment was performed by the same method as that of Comparative Example 4 in which a short path was present, and the results shown in Table 1 were obtained. Comparative Example 6 At the tip of a full flight screw having a diameter of 40 mm, FIG.
Using a single-screw extruder equipped with a dalmage-type kneading element having a short path as shown in (1), the cylinder temperature was heated to 220 ° C. with an electric heater, and the hopper was filled with resin powder at a screw rotation speed of 100 rpm. The resin was melt-kneaded and the resin was extruded from the extruder die tip. For the test, the polypropylene resin composition (1) used in Example 1 was used. The fish eye measurement values of the obtained pellets were as shown in Table 1.

Comparative Example 7 As a test raw material, a polypropylene resin composition (2)
An experiment was carried out in the same manner as in Comparative Example 6 except that was used, and the results shown in Table 1 were obtained.

[0022]

[Table 1]

[0023]

According to the present invention, fish eyes, which are an obstacle to product quality, can be eliminated by an extruder, which has not been able to be done before. A good quality polypropylene resin composition can be produced under industrially advantageous conditions without impairing the properties. Further, since the removal of fish eyes in the present invention is performed after the resin is completely melted, there is an advantage that kneading energy required for removing fish eyes can be saved. This not only provides a stable supply method of a good quality polypropylene resin composition with little fish eyes, but also saves energy resources and protects the global environment, and is of great industrial value.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of an extruder of the present invention.

FIG. 2 is a side view of a kneading element A.

FIG. 3 is a sectional view taken along line XX of FIG. 2;

FIG. 4 is a side view of a kneading element B.

FIG. 5 is a screw configuration side view of CMP65X manufactured by Japan Steel Works.

FIG. 6 is a side view of a dalmage type kneading element (a).
(A) FIG.

[Explanation of symbols]

2 Single-screw extruder 3 Single-screw extruder capable of mounting kneading elements as segments 4 Cylinder 5 Introductory groove 6 Flight tip section 7 Discharge groove f Flow direction of resin

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shogo Okumura 3-10, Shiodori, Kurashiki-shi, Okayama Japan Polychem Co., Ltd. Mizushima Technical Center (72) Inventor Shinji Hashizume 1-6-14 Edobori, Nishi-ku, Osaka-shi, Osaka F-term (reference) 4F201 AA04E AA11K AA45 AB06 AB11 AB12 BA01 BD05 BK02 BK13 BK26 BK34 BK36 BK40 BK46 BK49 BN05 BN11 BN18 BN39 BQ16 BQ18 4F207 AA04E AA11K AA45 AB06 AB11 AB12 KA01 KA17 KF03 KK11 KK23 KK43 KL04 KL22 KL23 KL34 KL38 KL39 KL45 KL93 4J12 BB05X BB05X

Claims (7)

[Claims] 1. An extruder for a polypropylene-based resin composition containing an elastomer component comprising a heterogeneous α-olefin copolymer, which is mainly located before a kneading section and serves to completely melt the resin. And, it is an element that can impart shear strain uniformly to the molten resin,
In addition, the A value calculated by the following equation (1) is 10
An extruder characterized by comprising a kneading section having a kneading element which can be ⁹ or more. Formula (1) A = η · Σ (S) · n (1) (where, η represents the shear viscosity of the resin in the kneading portion, S represents the amount of shear strain in each flight portion of the element, and n Represents the number of shear strains applied to the resin by element flight.) 2. An element capable of imparting a uniform shearing strain is provided in the barrel and in the barrel and connected to the screw, a series of longitudinal introduction grooves closing and terminating in the resin outlet direction, and a series of longitudinal introduction grooves in the resin inlet direction. 3. The extruder of claim 1 wherein the extruder is an element comprising a cylinder having a series of longitudinal discharge grooves that terminate and close, and a septum (flight) having clearance between the grooves and between the inner wall of the barrel. 3. The extruder according to claim 1, wherein a cylinder cooling device is provided on an outer peripheral portion of the cylinder of the kneading section. 4. The degassing device according to claim 1, further comprising a degassing device for devolatilizing the liquid added between the liquid addition nozzle positioned before the kneading unit inlet and the kneading unit outlet and the extrusion die. Extruder. 5. The extruder according to claim 1, further comprising a clearance adjusting valve capable of arbitrarily adjusting the clearance. 6. The extruder according to claim 1, further comprising a screen changer that can be arbitrarily changed during operation of the screen mesh before the extrusion die. 7. The extruder according to claim 1, wherein the extruder is a two-stage extruder comprising an extruder for melting and an extruder for kneading.