JP2006021467A - Method for preventing occurrence of cutting powder in pelletization of thermoplastic resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily obtain thermoplastic resin pellets which scarcely receive restrictions such as the temperature control of strands and the addition of a water tank during the production of pellets, suppress the occurrence of cutting powder adherent to or mixed in the pellets to reduce the cutting powder, suppresses the fault of a pellet production line caused by the cutting powder, improves continuous productivity, reduces a filter replacement frequency, and improves faults during molding, for example a defective appearance such as color nonuniformity during molding. <P>SOLUTION: In a method in which the strands obtained by melting/kneading the thermoplastic resin, after being cooled, are cut into the pellets, polycaprolactone is mixed in advance with the thermoplastic resin, and the mixture is melted/kneaded, or the polycaprolactone is mixed with the molten thermoplastic resin, and the mixture is melted/kneaded. In this way, the occurrence of the cutting powder in the pelletization can be prevented. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for preventing the generation of cutting powder in pelletization, which comprises blending polycaprolactone with a thermoplastic resin, particularly a transparent thermoplastic resin. Specifically, it is intended to suppress the generation of cutting powder adhering to or mixed with the pellets of the thermoplastic resin after pelletization, and as a result, to provide a molding resin material consisting of pellets with less fine powder. Production line defects due to clogging, for example, clogging of air filter due to cutting powder adhering to the pellet feed line, contamination when switching to another grade, cutter cutting failure in strand cutter equipment The maintenance frequency of the production line is reduced, contributing to the improvement of continuous and stable productivity.Furthermore, defects during molding, for example, in drying equipment such as hopper dryers, from pellet receiving tanks and receiving tanks to hopper dryers. When cutting powder adhering to the air feed line is switched to another material And contamination, is to provide a resin pellet having improved like appearance such as color unevenness in molding defects.

  Thermoplastic resins are used in various applications because of their excellent characteristics. In particular, transparent thermoplastic resins are widely used in the fields of electricity, electronics, OA, automobiles, etc. because of their excellent light transmission properties, and resins that satisfy the required performance required in each field are selected. Have been used properly.

On the other hand, the form of the raw material for forming is provided as a pellet shape. As a method for producing the processing pellets, it is melt-kneaded by an extruder or the like, extruded as a strand-like molten resin from the die at the tip of the extruder, rapidly cooled in a water tank, and then 2 to 4 mm long by a pelletizer. It is cut into a cylindrical pellet of the degree. In this cutting process, fine cutting powder is generated in addition to pellets having a desired shape. The cutting powder is deposited and mixed in the roll cutter portion of the pelletizer, the pellet conveying line after the pelletizer, and the packing bag.

Due to the mixing of the cutting powder in the pellet production line, much time and labor are required for maintenance such as cleaning of the roll cutter unit, the conveying line, and the air filter for cutting powder removal and replacement of parts. Further, the cutting powder mixed in the packed pellets adheres to drying equipment such as a conveyance line from pellet reception to a molding machine, a hopper dryer, and a hot-air circulation type shelf oven in injection and extrusion molding. In such a molded product process, the cutting powder causes contamination particularly when it is replaced with another material such as a different color, and presents as color unevenness or foreign matter in the appearance of the product, causing appearance defects. In order to prevent such problems, it has been desired to reduce the cutting powder generated when the melt-kneaded thermoplastic resin strand is cooled and then pelletized using a pelletizer or the like.

Conventionally, with respect to a method for reducing the generation of cutting dust during pellet production, a method for strictly controlling the cutting temperature when cutting a strand, or a pellet after passing through a plurality of water tanks with different temperatures in strand cooling There are proposals to make it possible.
JP 2001-269929 A Japanese Patent Laid-Open No. 11-342510

  However, in the conventional technique, in order to suppress the amount of cutting dust generated in the process of pelletizing the thermoplastic resin, the temperature control of the water tank and the strands must be strict, and special additions such as addition of water tanks and temperature control are required. Needed equipment and equipment. Furthermore, in the production of pellets, the amount of cutting powder must be strictly controlled, and a great deal of labor has been expended.

  As a result of intensive studies in view of such problems, the inventors of the present invention remarkably suppresses the generation of cutting powder in pelletizing strands by blending polycaprolactone with the thermoplastic resin, and consequently adheres to or mixes with the pellets. The present inventors have found a method for reducing cutting powder to be achieved and have reached the present invention.

  That is, the present invention is characterized in that, in a method of cooling and stranding a strand obtained by melt-kneading a thermoplastic resin and then cutting into pellets, the thermoplastic resin is previously blended with polycaprolactone and melt-kneaded. The present invention provides a method for preventing the generation of cutting powder during pelletization.

Further, as another embodiment of the present invention, in a method in which a strand obtained by melt kneading a thermoplastic resin is cooled and then cut and pelletized, polycaprolactone is blended with a molten thermoplastic resin and melt kneaded. The present invention provides a method for preventing generation of cutting powder in pelletization.

  According to the method for preventing the generation of cutting powder in pelletization of the present invention, it is difficult to receive restrictions such as temperature control of the strand during pellet production and addition of a water tank, and the generation of cutting powder adhering to or mixing with the pellet is suppressed. As a result, thermoplastic resin pellets with less cutting powder are obtained, and defects in the pellet production line due to the cutting powder, for example, improvement in continuous stable productivity and reduction in maintenance frequency, and further, defects during molding, For example, in the drying equipment such as a hopper dryer, the cutting powder adhering to the pellet receiving tank and the air feed line from the receiving tank to the hopper dryer is contaminated when switching to another material, and color unevenness during molding It is possible to easily obtain thermoplastic resin pellets with improved appearance defects.

  Examples of the thermoplastic resin used in the present invention include polycarbonate resins, polymethyl methacrylate, polystyrene, acrylonitrile / styrene copolymers, methacrylate / styrene copolymers, and styrene copolymers such as acrylonitrile / butadiene / styrene copolymers. , Polyester, polyetherimide, polyimide, polyamide, modified polyphenylene ether, polyarylate, cycloolefin polymer, polymer alloy obtained by blending polycarbonate and polyester, and the like. In particular, a polycarbonate resin which is a transparent thermoplastic resin, polymethyl methacrylate, methyl methacrylate / styrene copolymer, polyarylate, styrene copolymer or cycloolefin polymer is preferably used. The transparent thermoplastic resin is a material that transmits light and that allows the observer to recognize the object when the molded article of the resin is interposed between the observer and an object such as a light source. It has transparency.

Furthermore, the polycarbonate resin used in the present invention is a polymer obtained by a phosgene method in which various dihydroxydiaryl compounds and phosgene are reacted, or a transesterification method in which a dihydroxydiaryl compound and a carbonate such as diphenyl carbonate are reacted. Typical examples include polycarbonate resin produced from 2,2-bis (4-hydroxyphenyl) propane (bisphenol A). Further, the dihydroxyaryl compound and a trivalent or higher phenol compound such as phloroglucin, 4,6-dimethyl-2,4,6-tri- (4-hydroxyphenyl) -heptene, 2,4,6-dimethyl-2, 4,6-tri- (4-hydroxyphenyl) -heptane, 1,3,5-tri- (4-hydroxyphenyl) -benzol, 1,1,1-tri- (4-hydroxyphenyl) -ethane and 2 , 2-bis- [4,4- (4,4′-dihydroxydiphenyl) -cyclohexyl] -propane or the like may be used in combination.

The polycaprolactone used in the present invention is produced by ring-opening polymerization of ε-caprolactone in the presence of a catalyst, and in particular, a homopolymer of 2-oxepanone is preferably used. The polymer is easily available as a commercial product, and examples include tone polymer manufactured by Dow Chemical Company, CAPA manufactured by Solvay Company, and the like. The viscosity average molecular weight of polycaprolactone is preferably 10,000 to 100,000, more preferably 40,000 to 90,000.

  Furthermore, when ring-opening polymerization of ε-caprolactone, one modified with 1,4-butanediol or the like, or modified polycaprolactone substituted at the molecular terminal with an ether or ester group may be used.

In the present invention, other known additives such as antioxidants, ultraviolet absorbers, lubricants, mold release agents, colorants, fillers, fluidity improvement are added to the thermoplastic resin as long as the effects of the present invention are not impaired. An agent, a spreading agent, an impact resistance improving agent, and the like can be added as necessary.

  Regarding the method of blending and kneading polycaprolactone with the thermoplastic resin of the present invention, the thermoplastic resin and polycaprolactone are weighed in an arbitrary blending amount, mixed with a tumbler, ribbon blender, high-speed mixer, etc., and then mixed. Can be melt-kneaded using an ordinary single-screw or twin-screw extruder, or each component can be weighed separately and introduced into the extruder from a plurality of feeders and melt mixed. And, when these components are melted and mixed, arbitrary conditions can be selected according to the situation, such as the position to be fed into the extruder, the extrusion temperature, the screw rotation speed, and the supply amount.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples, unless the summary is exceeded.

The thermoplastic resin and polycaprolactone used are as follows.
Polycarbonate resin:
Caliber 200-30 manufactured by Sumitomo Dow
(Viscosity average molecular weight: 17200, hereinafter abbreviated as PC)
Polycaprolactone:
CAPA6400 made by Solvay
(Viscosity average molecular weight: 37000, hereinafter abbreviated as PCL-1)
CAPA6800 manufactured by Solvay
(Viscosity average molecular weight: 80000, hereinafter abbreviated as PCL-2)
Tone polymer P-787 manufactured by Dow Chemical Company
(Viscosity average molecular weight: 80000, hereinafter abbreviated as PCL-3)
Colorant:
RCL-4 manufactured by Millennium Inorganic Chemicals
(Titanium dioxide, abbreviated as colorant)

Moreover, the analysis / evaluation method of the obtained thermoplastic resin pellet is as follows.
(Evaluation of cutting dust generation)
The condition of the roll cutter and pellet discharge port of the pelletizer at the time when 15 minutes had elapsed after the start of strand cutting by the pelletizer was visually observed, evaluated based on the following criteria, and ○ and Δ were good.
○: No adhesion of cutting powder to the roll cutter and pellet outlet.
Δ: Slight adhesion of cutting powder is observed at the roll cutter and pellet outlet.
X: Adhering of cutting powder is remarkably observed at the roll cutter and pellet outlet.

(Evaluation of appearance defects in molded products)
About 2 kg of the obtained pellets were supplied into an injection molding machine hopper dryer, and the inside of the injection molding machine cylinder was washed until the pellets disappeared. Next, the PC is put into an empty hopper dryer, and after purging the cylinder five times with the PC, continuous molding is performed to check for uneven color and foreign matter on the molded product after the fifth shot. This was done visually.

Example 1
PC (99%), PCL-1 (1%), and a colorant (0.2 parts) were dry-mixed with a super floater manufactured by Kawata according to the blending ratio shown in Table 1. Next, it was melt-kneaded at a temperature of 250 ° C. by a single-screw extruder VS-40-32 (shaft diameter = 40 mmφ, L / D = 32, A in FIG. 1) manufactured by Tanabe Plastics Co., Ltd. The extruded strand was immediately guided to a cooling water tank, and the strand was cut and pelletized at a take-up speed of 16 m / min using an SS type pelletizer manufactured by Nippon Placon. The water temperature of the 1st tank (B of FIG. 1) and the 2nd tank (C of FIG. 1) of the cooling water tank at this time were 55 degreeC and 45 degreeC, respectively. Moreover, the cooling time in the 1st water tank and the 2nd water tank of the strand was 0.75 second and 1.1 second, respectively.

  15 minutes after starting the strand cutting, the pellet processing was stopped, and the state of the cutting powder adhering to the roll cutter part (D in FIG. 1) and the pellet discharge port (E in FIG. 1) of the pelletizer was visually observed. However, the adhesion of the cutting powder was only slightly observed, and the adhesion state was small and good (FIGS. 4 and 5).

  Next, about 2 kg of the obtained pellets were put into a hopper dryer of an injection molding machine J100-EIIP manufactured by Nippon Steel Works, and the inside of the cylinder was purged at a melting temperature of 280 ° C. until the pellets disappeared. Next, after putting the PC into the hopper dryer and repeating the weighing and purging operations 5 times, continuous molding was performed with the PC, and a molded product having a width of 50 mm, a length of 90 mm, and a thickness of 2 mm was collected. Subsequent color unevenness and foreign matter in the molded product were confirmed by visual observation.

(Example 2)
Pelletization was performed under the same melt kneading conditions and take-up speed as in Example 1 except that the blending ratio of PC and PCL-1 was 97% and 3%, respectively. The water temperature of the 1st tank at this time was 52 degreeC, and the water temperature of the 2nd tank was 44 degreeC. There was no adhesion of cutting powder at the roll cutter part and the pellet discharge port, and it was good, and good appearance was not observed due to injection molding.

Example 3
Pelletization was carried out under the same melt kneading conditions and take-up speed as in Example 1 except that the type and blending ratio of PCL were PCL-2 and 3%, respectively. The water temperature of the 1st tank at this time was 55 degreeC, and the water temperature of the 2nd tank was 45 degreeC. There was no adhesion of cutting powder at the roll cutter part and the pellet discharge port, which was good (FIGS. 6 and 7), and good appearance was not observed due to injection molding.

Example 4
Pelletization was carried out under the same melt kneading conditions and take-up speed as in Example 1 except that the type and blending ratio of PCL were PCL-3 and 3%, respectively. The water temperature of the 1st tank at this time was 53 degreeC, and the water temperature of the 2nd tank was 43 degreeC. There was no adhesion of cutting powder at the roll cutter part and the pellet discharge port, and it was good, and good appearance was not observed due to injection molding.

(Example 5)
Example 1 except that PC and PCL-3 were not dry-mixed by a super floater, and the PC and PCL-3 were respectively charged directly into the extruder from two feeders so that PC and PCL-3 would be 90% and 10%, respectively. Pelletization was performed under the same melt-kneading conditions and take-up speed. The water temperature of the 1st tank at this time was 51 degreeC, and the water temperature of the 2nd tank was 42 degreeC. There was no adhesion of cutting powder at the roll cutter part and the pellet discharge port, and it was good, and good appearance was not observed due to injection molding.

(Comparative Example 1)
Pelletization was performed under the same melt-kneading conditions and take-up speed as in Example 1 except that PC was 100%. The water temperature of the 1st tank at this time was 51 degreeC, and the water temperature of the 2nd tank was 43 degreeC. When the state of attachment of the cutting powder at the roll cutter part and the pellet discharge port was confirmed, a large amount of cutting powder was attached (FIGS. 2 and 3), and it took a lot of time to remove the cutting powder. Moreover, when the appearance defect by injection molding was confirmed, a white streak-like pattern and a foreign material were seen in the molded product, and a favorable product was not obtained.

FIG. 1 is a schematic view showing the steps of melt-kneading, cooling, and pelletizing of the present invention. FIG. 2 is a photograph of the roll cutter portion of the pelletizer in Comparative Example 1. FIG. 3 is a photograph of the pellet outlet of the pelletizer in Comparative Example 1. FIG. 4 is a photograph of the roll cutter portion of the pelletizer in Example 1. FIG. 5 is a photograph of the pellet outlet of the pelletizer in Example 1. FIG. 6 is a photograph of the roll cutter portion of the pelletizer in Example 3. FIG. 7 is a photograph of the roll cutter portion of the pelletizer in Example 3.

Explanation of symbols

A: Extruder B: First tank C: Second tank D: Pelletizer body E: Roll cutter F: Pellet outlet G: Strand

Claims (6)

  A cutting powder in pelletization characterized in that a strand obtained by melting and kneading a thermoplastic resin is cooled, then cut and pelletized, and the thermoplastic resin is previously blended with polycaprolactone and melt kneaded. How to prevent the occurrence of   Cutting in pelletization characterized by blending polycaprolactone in a molten thermoplastic resin and melt kneading in a method of cutting and pelletizing a strand obtained by melting and kneading a thermoplastic resin A method to prevent the generation of powder.   The method for preventing generation of cutting powder in pelletization according to claim 1 or 2, wherein the thermoplastic resin is a transparent resin.   The pellet according to claim 1 or 2, wherein the thermoplastic resin is polycarbonate resin, polymethyl methacrylate, methyl methacrylate / styrene copolymer, polyarylate, styrene copolymer resin, or cycloolefin polymer. A method to prevent the generation of cutting powder in the process   The amount of polycaprolactone blended is 0.1 to 15% by weight (based on the thermoplastic resin before blending), and generation of cutting powder in pelletization according to claim 1 or 2. How to prevent. The viscosity average molecular weight of polycaprolactone is 40000-90000, The method of preventing generation | occurrence | production of the cutting powder in the pelletization of Claim 1 or Claim 2 characterized by the above-mentioned.

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