JPH05285941A - Kneading method for resin composition - Google Patents

Abstract

PURPOSE:To protect strands from cutting out by regulating the ratio of residence time in a completely melting zone and an incompletely melting zone when a thermoplastic resin composition is melt kneaded by using a screw extruder. CONSTITUTION:An extruder usually used for melt kneading can be used. In melt kneading by a screw extruder, resin is fed out of a raw material feed inlet 4 and fed to an incompletely melting zone 1 set in forward flight in the non-molten or semi-molten state, melted in a kneading disk or a zone 2 set in reverse flight, passed through the melting zone 3 set in forward flight and fed to a dice 7. When the process from the zone 2 for melting the resin up to the dice 7 is divided as a completely melting zone, the residence time in the completely melting zone is set less than eight times as much as the residence time of the incompletely melting zone 1. As a resin composition to be used, a composition of thermoplastic resin of comparative high melting point and resin of low thermal stability or an additive, or a composition of accelerating decomposition by the mutual action is suitable.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for kneading a thermoplastic resin composition. Specifically, the composition of a resin having a relatively high melting point and an additive or resin having low thermal stability, or the resin composition in which the resin and an additive or another resin may interact (react or decompose) The present invention relates to a method of melting and mixing while suppressing breakage and the like.

[0002]

2. Description of the Related Art As a method for mixing a flame retardant, a mold release agent, a heat stabilizer and the like with a thermoplastic resin, a method in which a strand is formed by a screw extruder and pelletized and melt-kneaded is often performed. . In this case, conventionally, a method has been adopted in which the melting zone is lengthened to improve dispersion and mixing mainly by shearing in the complete melting zone. In this case, the residence time in the complete melting zone is usually 10 times or more that in the incomplete melting zone.

Further, when the kneading conditions are improved, it is usual to improve the set temperature of the barrel heater and the rotation speed of the extruder screw.

[0004]

However, when a resin having a relatively high melting point and an additive having a relatively low thermal decomposition temperature are kneaded by a conventional method, or when the additive interacts with the resin and decomposes. However, there are problems that the quality of the product is deteriorated due to the decomposition of the additive, the coloration of the resin composition, and the like, and that strand breakage occurs during kneading and the yield is decreased.

[0005]

Means for Solving the Problems As a result of intensive studies made by the present inventors, strand knitting is significantly suppressed by bringing a kneading disk for melting a resin closer to a die to shorten a residence time in a complete melting zone. The inventors have found out what can be done and have reached the present invention. That is, the gist of the present invention is characterized in that, in a method of melt-kneading a thermoplastic resin composition using a screw extruder, the residence time in the complete melting zone is less than 8 times the residence time in the incomplete melting zone. It lies in a method of kneading a resin composition. Hereinafter, the present invention will be described in detail.

In the present invention, melt kneading is performed using a screw extruder. The extruder may be of any type as long as it is an extruder normally used for melt-kneading, and examples thereof include a single-screw extruder, a twin-screw same-direction screw extruder, and a twin-screw different-direction screw extruder. To melt and knead with a screw extruder, the raw material resin is fed from the feeder (raw material supply port) into the barrel, and the screw element is first fed forward to feed the resin in an unmelted or semi-molten state, then the screw element is fed. The resin is melted by applying high shear with a kneading disk or reverse flight, the molten resin is fed again in the forward flight, and the molten resin is extruded from the die. The barrel temperature is usually set to a temperature 0 to 50 ° C. higher than the melting point of the resin.

In the present invention, the zone for sending the non-melting or semi-melting resin in the forward flight is defined as the incomplete melting zone, and the melting zone from the zone where the resin is melted by high shear such as kneading to the die is defined. When defined as a complete melting zone, it is an essential condition that the residence time of the resin in the complete melting zone is less than 8 times the residence time in the incomplete melting zone. Preferably, the residence time ratio between the incomplete melting zone and the complete melting zone is 1: 3 to 1: 8.

If the complete melting zone is long, the power load is high,
In addition, thermal decomposition of the additives and resin components occurs, and foaming due to decomposition of the additives causes strand breakage, which is not preferable because the production stability decreases. Conversely, if the melting zone is too short, unmelted resin may be generated, which is not preferable. The residence time ratio between the complete melting zone and the incomplete melting zone can be set by changing the screw configuration and setting the position of the kneading disk to an appropriate position. The residence time (conveyance time) per unit element of the screw
Is 2 to 10 times larger in the melting zone as compared to the incomplete melting zone, as shown in Table-1. Therefore, in order to make the residence time ratio of incomplete melting zone: melting zone = 1: 3 to 1: 8, the incomplete melting zone is half or more in the general type screw length.

[0009]

[Table 1]

The target resin composition of the present invention is a composition of a thermoplastic resin having a relatively high melting point and a resin or an additive having a low thermal stability, or a composition which promotes the decomposition of the resin or the additive by interaction. Are suitable. Specifically, examples of the former include PBT / ABS, PCR / ABS, PA / ABS,
Polymer alloy or polymer blend such as PA / PP, PA / PE, or PCR, PBT, PET, PA
An example of such a composition is a polymer having a relatively high melting point such as, and a release agent having a low decomposition temperature, a pigment, a flame retardant, a heat stabilizer, and an impact modifier. An example of the latter is PB
Polymer alloy or polymer blend such as T / PET, PCR / PET, PCR / PBT, or PBT,
Examples thereof include polymer alloys or polymer blends of PCR, PA and the like with butadiene rubber, acrylic rubber and the like. (However, PBT is polybutylene terephthalate,
PET is polyethylene terephthalate, ABS is acrylonitrile-butadiene-styrene copolymer, PCR is polycarbonate, PA is polyamide, PP is polypropylene, and PE is polyethylene. )

[0011]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples as long as the gist thereof is not exceeded. In the following examples, Tex44ss-30AN-ZV was used as the extrusion model and nylon-66 (Zyte manufactured by DuPont) was used as the raw material composition.
l FE3218; η _rel 2.8) 100 parts by weight and melamine cyanurate (flame retardant; Ogaki Kasei Co., Ltd., MX
-44, particle size 325 mesh, decomposition start temperature 270-3
(00 ° C.) 5 parts by weight of a composition was used. The temperature of each barrel heater was 270 to 280 ° C. Extrusion amount is the same except for Example 3.

Comparative Example 1 (Conventional Method) Melt kneading was carried out with a screw pattern as indicated by I in FIG. 1 (the arrow in the figure indicates the flow direction of the resin). The residence time ratio was incomplete melting zone: melting zone = 1: 14. As a result, the power load of the screw motor is 85
At A (ampere), the strand breakage was 15 times in 30 minutes. Further, foaming of the resin composition was also observed.

Example 1 Melting and kneading were carried out while changing the screw pattern as shown by II in FIG. The residence time ratio was 1: 3. As a result, the power load was reduced to 68 A and strand breaks were no longer observed.

Example 2 The screw pattern was changed as indicated by III in FIG. The residence time ratio was 1: 5. As a result, the power load is 75
It was A and no strand break was observed.

Example 3 The same as Example 1 except that the extrusion rate was 1.3 times. (The residence time ratio remains 1: 3.) Power load is 80A
No strand break was observed. From this result, it is understood that the method of the present invention can not only suppress strand breakage but also increase the throughput.

Comparative Example 2 The screw pattern was as shown by II in FIG. 1 and the raw materials were fed from the side feeder 6 and melt-kneaded. This comparative example corresponds to the case where the melting time is shortened by using a short extruder. The residence time ratio was 1: 8. No strand break was observed, but the power load increased to 87A.

Comparative Example 3 Same as Example 1 except that the residence time ratio was 1: 2.
The resin contained an unmelted portion and was not uniformly dispersed.

[0018]

The strand breakage can be suppressed by the method of the present invention, so that the yield can be improved. Also,
Since the power load is reduced, the amount of extrusion can be increased and the amount of production can be increased accordingly.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a screw pattern of an extruder of an example.

[Explanation of symbols]

 1 Incomplete Melting Zone 2 Zone for Melting Resin by High Shear 3 Melting Zone 4 Raw Material Supply Port (Excluding Comparative Example 2) 5 Vent Port 6 Side Feeder 7 Dice

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshitaka Shiraishi 1-1 Kurosaki Shiroishi, Hachimansai-ku, Kitakyushu City Mitsubishi Kasei Co., Ltd. Kurosaki Plant

Claims (1)

[Claims] 1. A method for melt-kneading a thermoplastic resin composition using a screw extruder, wherein the residence time in the complete melting zone is less than 8 times the residence time in the incomplete melting zone. Method of kneading things.