JP2005262824A - Screw for resin extrusion, and molding method for molded article colored in pattern - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a screw for resin extrusion and a molding method which can mold an article colored in pattern stably without relating to a molding method and dropping formability and productivity. <P>SOLUTION: The screw for resin extrusion having a feed zone FZ, a compression zone CZ, and a metering zone MZ has a heating zone HZ for heating a resin while suppressing mixing of a resin at the part from the metering zone MZ to the tip section of the screw. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a resin extrusion screw and a method for molding a pattern-colored product. More specifically, the present invention relates to a resin extrusion screw capable of increasing the heating efficiency and a pattern coloring product molding method using an extruder equipped with the screw.

As a molding technique for producing a wood grain appearance by original deposition, a technique related to a pigment masterbatch (see Patent Documents 1 and 2), a technique related to a blow molding machine (Patent Document 3), and a die structure of other extruders have been proposed. ing.
The technique described in these and the pattern original deposition technique similar to this are techniques for adjusting the molten state of the pattern coloring pigment master batch in the extrusion process and coloring the pattern on the surface of the molded product.

JP 2001-294671 A JP 2003-238695 A JP 2002-96376 A

  In the above-described coloring technique, during the molding process, the pigment dispersion is suppressed in the plasticizing extruder, the pattern coloring pigment master batch is sufficiently melted by the subsequent dies, and the flow pattern is colored in the dies. There is a need. Such a melting suppression of the pigment master batch can be relatively easily performed by a large blow molding machine having a large crosshead having a large heat capacity and a stable temperature.

However, continuous blow molding machines with many small crossheads and extrusion molding machines with small dies have few heating parts after the plasticizing extruder and a large amount of extrusion. Difficult to melt and easy to cause poor coloring.
That is, the continuous blow molding method and the extrusion molding method using a small die have a small crosshead and a small die and a short flow path. In the pattern coloring molding method, since the resin temperature is extruded at a relatively low temperature in order to suppress pigment dispersion in the plasticizing extruder, it is necessary to heat the resin at a high speed from the extruder to the die outlet. However, since the crosshead and the die are small, it is difficult to supply heat, and the resin extrusion speed is high. Therefore, the supply of heat is insufficient, and the pigment master batch is likely to be insufficiently melted.

For this reason, the temperature of the crosshead and the die will be raised, but the inside of the extruded resin cannot be heated uniformly to the extent that it is heated from the outside of the crosshead or the die with a heater, etc. It is difficult to heat the resin inside because it is hot. In addition, if only the surface is overheated, the surface pattern that has come out is likely to be dispersed and returned to reduce the surface coloring. For this reason, molding is often difficult and productivity is often lowered.
On the other hand, it is conceivable to improve by increasing the size of the crosshead or the die, but in general, modification is often difficult due to the basics of the machine and the connection.

Japanese Patent Laid-Open No. 9-267375 proposes that the melting control of the pattern coloring pigment master batch is performed by adjusting the rotational speed of the extruder and the cylinder temperature. In this method, the screw L (effective This is not realistic because the influence of length) / D (outer diameter), compression ratio, etc. is great and productivity is also reduced.
Under such circumstances, the pattern coloring pigment master batch can be used in continuous blow or extrusion molding to color the pattern while controlling the melting, without causing appearance defects due to the influence of the molding conditions, and a highly productive pattern coloring molding method. It has been demanded.

  An object of the present invention is to provide a screw for resin extrusion and a molding method capable of stably molding a pattern-colored product regardless of the molding method without reducing moldability and productivity.

The resin extrusion screw according to the present invention is a resin extrusion screw having a feed zone, a compression zone, and a metering zone, for heating the resin while suppressing mixing of the resin from the metering zone to the screw tip. It has a heating zone.
The heating zone is not a zone intended for mixing (kneading), but a zone intended to efficiently heat the resin to a constant temperature by utilizing a stirring action by a screw. For this reason, the heating zone has a screw design that suppresses resin kneading. Therefore, the pattern-colored product can be molded stably without reducing moldability and productivity regardless of the molding method.

In the resin extrusion screw according to the present invention, a screw groove is formed in the heating zone, and the screw groove in the heating zone is at least one of a groove pitch and a groove depth with respect to the screw groove in the metering zone. Are preferably formed in different dimensions.
Design values that affect kneading are the groove pitch and groove depth of the screw grooves, and the compression ratio is determined by these values, and the kneading force is generally determined by the size of the compression ratio. The compression ratio is expressed by how much is compressed with respect to the groove volume between one groove pitch of the feed zone (resin biting port). Generally, the groove volume between one groove pitch of the feed zone is Vf, When the groove volume between one pitch of the metering zone (generally, the tip portion of the screw) is Vm, the compression ratio is represented by CR = Vf / Vm.
In the resin extrusion screw of the present invention, the compression ratio CRm of the metering zone may be equal to the compression ratio CRh of the heating zone, but the screw groove in the heating zone is the screw groove of the metering zone. On the other hand, at least one of the groove pitch and the groove depth is formed in a different dimension. In other words, even if the compression ratio is the same, if the groove depth is increased and the groove pitch is reduced, the forward feed speed is reduced, and conversely, the groove depth is reduced and the groove pitch is increased. It will be faster. Thus, since the feed speed of the resin can be adjusted even with the same compression ratio, the temperature can be adjusted by changing the residence time of the resin in the screw.

In the screw for resin extrusion according to the present invention, the compression ratio CRm obtained by dividing the groove volume between one groove pitch of the screw grooves in the feed zone by the groove volume between one groove pitch of the screw grooves in the metering zone; The compression ratio CRh obtained by dividing the groove volume between one groove pitch of the screw grooves in the feed zone by the groove volume between one groove pitch of the screw grooves in the heating zone is CRm> CRh. Is preferred.
In the case of the resin extrusion screw of the present invention, the compression ratio CRh calculated in the heating zone is smaller than the compression ratio CRm calculated in the metering zone. In other words, the plasticizing and kneading of the resin is completed up to the metering zone, and thereafter, the entire resin is uniformly and efficiently heated in a short time while the kneading is gently performed and the resin is stirred. It has become.

In the resin extrusion screw of the present invention, at the boundary between the metering zone and the heating zone, the groove pitch is gradually decreased and the groove depth is gradually increased from the metering zone to the heating zone. It is preferable that a screw groove is formed.
When the difference between the compression ratio CRm of the metering zone and the compression ratio CRh of the heating zone is large, the pressure suddenly drops at the boundary and a surging phenomenon or the like may occur, and the extrusion amount may become unstable. . For this reason, since it is not preferable to suddenly change the compression ratio between the metering zone and the heating zone, it is necessary to gradually decrease the compression ratio near the connection between the metering zone and the heating zone.
In the screw for resin extrusion according to the present invention, the screw groove is formed so that the groove pitch becomes gradually smaller and the groove depth becomes gradually deeper from the metering zone toward the heating zone. It can prevent the amount of extrusion from becoming unstable due to a sudden drop in pressure and surging.

In the resin extrusion screw according to the present invention, it is preferable that the screw outer diameter Dh of the heating zone is smaller than the screw outer diameter Dm of the metering zone.
The screw outer diameter, screw thread width, etc. of the heating zone are not particularly limited, but in the resin extrusion screw of the present invention, the screw outer diameter Dh of the heating zone is smaller than the screw outer diameter Dm of the metering zone. With this configuration, the gap between the outer diameter of the screw in the heating zone and the inner diameter of the heating cylinder (barrel) increases, and the resin flows backward (backflow) over the screw groove in the heating zone, and the resin circulates and stays. It takes a long time to do. When this circulation retention occurs moderately, the heating zone can be shortened to efficiently heat the resin. However, if the resin circulates excessively, over-kneading and overheating occur, and the pattern is difficult to be produced due to pigment dispersion. Therefore, the screw outer diameter and the like need to be moderately large.

In the resin extrusion screw according to the present invention, it is preferable that the inner diameter of the screw groove of the metering zone is Dmb, and the heating zone is formed in a torpedo structure having an outer diameter equal to or less than the Dmb.
The purpose of providing the original torpedo is to provide a torpedo having a diameter larger than the outer diameter of the metering zone at the tip of the screw, thereby suppressing the amount of extrusion and increasing the back pressure and increasing the kneading strength.
In the screw for resin extrusion according to the present invention, the heating zone is formed in a torpedo structure having an outer diameter equal to or less than the inner diameter Dmb of the screw groove of the metering zone. In such a structure, no pressure increase occurs and the extrusion speed decreases. That is, the residence time can be increased without kneading the resin.

In the resin extrusion screw according to the present invention, the heating zone is preferably formed in a torpedo structure and includes at least one of a groove, a pin, and a stirring blade for increasing the heating efficiency of the resin. .
The heating zone of the torpedo structure does not knead the resin, but is easily heated because the resin is agitated by screw rotation.
Since the screw for resin extrusion according to the present invention includes at least one of a groove, a pin, and a stirring blade, the resin stirring can be promoted while mixing is suppressed. Therefore, more uniform heating can be expected.

In the screw for resin extrusion according to the present invention, when the screw outer diameter of the metering zone is Dm and the effective screw length including the heating zone is L, L / Dm is 20 or more, and the heating zone The length is preferably 2 Dm or more.
The screw of the present invention may have an L / Dm of 20 or more and a heating zone length of 2 Dm or more, preferably, an L / Dm of 24 or more and a heating zone length of If it is 2-6 Dm, the original kneading | mixing function of a screw will not be impaired.

In addition, although the maximum compression ratio of a screw is a metering zone part, the appropriate compression ratio of this site | part changes with material types. In PP (polypropylene) and HDPE (high density polyethylene), it is about 2 to 3, but 2.5 or less is preferable in the pattern coloring molding proposed in the present invention. If the compression ratio exceeds this, the pigment is dispersed up to the metering zone. If the compression ratio of a heating zone is below the compression ratio of a metering zone, there will be no problem in particular. For example, if the compression ratio of the metering zone portion is 2.4, the compression ratio of the heating zone gradually increases from 2.4 to 2.0 toward the tip from the connecting portion with the metering zone. Change to
In the heating zone of the torpedo structure, compression is hardly applied. For this reason, the pressure suddenly drops at the connecting portion with the metering zone, and surging or the like easily occurs. In order to prevent this, a breaker plate that provides an extrusion resistance is set at the tip of the extruder and the pressure is maintained. The pressure can be adjusted by adjusting the hole diameter and the number of holes in the breaker plate.

In the resin extrusion screw according to the present invention, the heating zone is preferably configured to be replaceable.
When the screw rotation increases, the resin feed speed generally increases, and the resin is likely to be underheated. In such a case, the screw groove is made deeper and the pitch is made narrower so that the feeding speed becomes slower in the heating zone. On the other hand, the molding may be performed at a low speed. In this way, when molding is performed with different rotational speeds using the same molding machine, a large number of screws is required if a screw is provided for each molding. To cope with this, if one screw is used up to the metering zone and the heating zone can be replaced, the heating zone can be changed according to the number of rotations, and the resin temperature suitable for pattern coloring can be changed. It can be obtained regardless of the rotational speed.

  The molding method of the present invention is a molding method in which a pattern-colored product is blow-molded by using an extruder equipped with the resin extrusion screw according to any one of the above-described ones. Heating is performed at a temperature that does not exceed the melting point of the master batch, and heating is performed at the heating zone above the melting point of the pattern coloring pigment master batch.

  Another molding method of the present invention is a molding method for extruding a pattern-colored product using an extruder equipped with any one of the above-described resin extrusion screws, up to the metering zone. Heating is performed at a temperature that does not exceed the melting point of the color pigment master batch, and heating is performed at or above the melting point of the pattern color pigment master batch in the heating zone.

  In the extruder equipped with the screw of the present invention, a heater zone for heating the cylinder of at least 4 zones is necessary. That is, heaters are required in the feed zone, compression zone, metering zone, and heating zone. Since the heating zone is usually shorter than the other zones, if the heater zone of the cylinder is equally divided, the heater of the heating zone may be applied in a part of the metering zone. Therefore, it is preferable that there is a heater zone that matches the length of the heater zone.

  If the pattern coloring master batch is dispersed in the plasticizing and kneading process, pattern coloring cannot be performed. Since the screw of the present invention is not different from an ordinary plasticized kneading screw up to the metering zone, the kneading force is strong. If the temperature is raised in this process, the pattern coloring master batch is dispersed and pattern coloring cannot be performed. For this reason, up to this zone, it is necessary to keep at least the melting point of the pattern coloring masterbatch, preferably, the Vicat softening point + 10 ° C. In the heating zone that has passed this, moderate diffusion is performed while suppressing kneading, and heating is performed at a melting temperature of the pattern coloring masterbatch that can be colored or higher, preferably at a melting temperature of + 10 ° C. or higher. Preferably, molding is more stable when the pattern coloring masterbatch is completely melted in the heating zone, but it is not essential that the patterning master batch is completely melted in the heating zone. That is, after leaving the extruder, the crosshead can naturally be heated with a die for the shortage. It is sufficient to heat at the heating zone to the extent that insufficient heating does not occur at the crosshead or die.

  In the heating zone, although kneading is suppressed, a diffusion action occurs, so that when the heating is performed at a temperature higher than the melting temperature of the pattern coloring masterbatch, a slight pigment dispersion occurs. However, this action returns and improves the coloring performance. That is, the pattern coloring masterbatch passes through the heating zone while being deformed by the rotation of the screw. After leaving the extruder, the pattern coloring pigment master batch is completely melted and distributed in the resin in a streak-like semi-dispersed state. In this semi-dispersed state, colored shading has already occurred, so it is not necessary to apply too much heat with the crosshead or the die, and if it is rectified and extruded with the crosshead or the die, it becomes a pattern close to light and dark wood grain stripes Become.

  In particular, if the crosshead or die has a drawing structure, it will be extruded with a stretched grid appearance. However, in such an extruded state, further heating with a crosshead or a die may return and cause an appearance defect. That is, if the inner surface temperature of the crosshead or the die is too high compared to the melting temperature of the pattern coloring pigment master batch, the pigment that has undergone pattern coloring is dispersed by the shearing action with the extrusion flow path surface, and the pattern is not good. This is for the sake of clarity. In the case of blow molding or extrusion molding using the screw of the present invention, the crosshead or die temperature should be equal to or lower than the resin temperature at the exit of the extruder, and extruded with the resin kept warm is a product with better appearance. Easy to obtain.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<Description of standard (conventional) screw>
FIG. 5 shows a structure of a general single-shaft single-screw (full flight) of an extruder for blow molding or extrusion molding. The screw is housed in an extruder cylinder and plasticizes the resin pellets while being rotated by a motor or the like. The resin pellets are bitten from the feed zone FZ, kneaded while being melted by heat and shearing heat in the compression zone CZ and the metering zone MZ, pushed forward, and finally sent to the crosshead or die. .

Since the feed zone FZ transports forward while biting the solid resin pellet, the depth of the screw groove is increased to make it easier to bite the resin pellet. In this feed zone FZ, frictional heat generation due to solid friction between resin pellets is large. External heating is also added to this, and the resin is gradually melted.
In the compression zone CZ, the groove depth of the screw groove gradually decreases. In this compression zone CZ, melting and kneading progress and the resin pressure increases. At the same time, the air that has been entrained with the resin and the vaporized component are pushed back and exhausted. When there is much vaporization, vacuuming may be performed from the outside of the cylinder. In this case, it is performed at a portion where no resin pressure is applied.

  The metering zone MZ is a zone for determining the extrusion amount. The groove depth of the screw groove in the metering zone MZ is constant and is the shallowest in the screw. This height determines the degree of compression and the amount of extrusion of the resin. If the groove depth of the screw groove is shallow, the degree of compression increases, the amount of extrusion decreases, and the degree of kneading increases. If the groove depth of the screw groove is deep, the degree of compression of the resin becomes small and the amount of extrusion increases. This degree of compression is called a compression ratio, but this compression ratio is not determined only by the groove depth ratio with the feed zone FZ. That is, it is determined by the groove volume between one groove pitch of the feed zone FZ and the groove volume between one groove pitch of the metering zone MZ, and is also related to the groove pitch. In this example, the groove pitch of the screw groove is the same in all zones.

<Description of Screw for Resin Extrusion of this Embodiment>
FIG. 1 shows a resin extrusion screw according to this embodiment. The present resin extrusion screw is different from the standard screw shown in FIG. 5 in that there is a heating zone HZ after the metering zone MZ. That is, up to the metering zone MZ, the screw groove is cut with the same dimensions as each zone in FIG. 5, but the length of the metering zone MZ is reduced, and the heating zone HZ is reduced by the reduced amount. Is provided. That is, the heating zone HZ is provided from the metering zone MZ to the screw tip. In this case, the feed zone FZ and the compression zone CZ may be reduced instead of reducing the length of the metering zone.
In the example of FIG. 1, when the outer diameter of the screw is D, a screw groove different from the screw groove of the metering zone MZ is provided with the length corresponding to approximately 5D as the heating zone HZ. That is, a screw groove having a dimension in which at least one of the groove pitch and the groove depth is different from the screw groove of the metering zone MZ is formed in the heating zone HZ. Here, screw grooves having different dimensions in both groove pitch and groove depth are formed.

  The heating zone HZ is not intended to knead the resin. That is, the object is to uniformly and efficiently heat the resin to the target temperature. Therefore, the resin is heated in the heating zone HZ by heat from an external heater, and mechanical heat generation such as shear heat generation is suppressed as much as possible. Specifically, the compression ratio is set smaller than that of the metering zone MZ. That is, the compression ratio CRm obtained by dividing the groove volume between one groove pitch of the screw grooves in the feed zone FZ by the groove volume between one groove pitch of the screw grooves in the metering zone MZ, and the screw groove in the feed zone FZ The compression ratio CRh obtained by dividing the groove volume between one groove pitch by the groove volume between one groove pitch of the screw grooves in the heating zone HZ is set to CRm> CRh. In the example of FIG. 1, the groove depth is made larger than that of the metering zone MZ, and the compression ratio is lowered.

  However, when the compression ratio suddenly decreases between the metering zone MZ and the heating zone HZ, pressure fluctuation occurs at that portion, and a surging phenomenon or the like occurs, and the extrusion tends to become unstable. For this reason, the device is being devised so that the pressure does not drop rapidly. In other words, making use of the fact that the deeper the groove depth is, the harder it is to knead, the deeper the groove, but the groove pitch is lowered so that the compression ratio is not greatly reduced, and the degree of reduction in the compression ratio is adjusted. Yes. Specifically, at the boundary between the metering zone MZ and the heating zone HZ, the groove pitch becomes gradually smaller and the groove depth becomes gradually deeper toward the heating zone HZ from the metering zone MZ. A screw groove is formed. As a result, the kneading of the resin can be suppressed without significantly reducing the pressure.

  In the heating zone HZ, the resin is uniformly heated with external heat transmitted while being agitated by the rotational action of the screw. This is an effect that cannot be obtained when heating with a crosshead or a die while being extruded in a laminar flow. The resin heating time and the like are adjusted by the groove pitch and the inclination angle of the screw groove. In the example of FIG. 1, the resin residence time is adjusted based on the result of narrowing the groove pitch and thread width, reducing the inclination angle, and consequently extending the length of the spiral groove. In this screw, the amount of extrusion itself does not change significantly from the standard screw in FIG. 5, but the residence time of the resin becomes longer.

The residence time varies depending on the resin extrusion amount and the required heating amount. However, since the length of the heating zone HZ affects the degree of kneading, it is taken as a guideline to take in the range of 2D to 6D depending on the effective length L of the screw. Here, when the screw outer diameter of the metering zone MZ is Dm and the effective screw length including the heating zone HZ is L, L / Dm is 20 or more and the length of the heating zone HZ is 2 Dm or more. (Range of 2Dm to 6Dm).
Another method for adjusting the residence time is a method in which the screw outer diameter Dh of the heating zone HZ is made smaller than the screw outer diameter Dm of the metering zone MZ. In such a screw, the resin in front of the extrusion direction causes a circulating flow that flows backward beyond the groove, and the residence time is extended by the amount of circulation. The amount of circulating resin is determined by the height of the groove, but if the circulation is not appropriate, it will be overheated.

The residence time is also related to the screw rotation speed. If the rotational speed is high, the amount of extrusion is naturally increased and the residence time is shortened. As the residence time is shortened, the temperature rise of the resin is insufficient. In this way, when the rotation speed is high, use a screw in the heating zone HZ that can take a residence time, and conversely, if the rotation speed is low, use a screw in the heating zone HZ that has a small resin residence time. Necessary. If there are both cases in the same extruder, production costs will be incurred if a screw is produced for each case. If only the heating zone HZ is replaced as a common screw up to the metering zone MZ, the production cost is low, and screw replacement and storage become easy.
For example, as shown in FIG. 2, a screw part P1 having a feed zone FZ, a compression zone CZ and a metering zone MZ and a screw part P2 having a heating zone HZ are configured separately, and this heating zone HZ Only the screw part P2 having a screw can be exchanged with the screw part P1 by an appropriate separating / coupling means (for example, a screw shaft having a male screw formed on the outer periphery and a screw hole having a female screw formed on the inner peripheral surface). May be.

<Description of Screw for Resin Extrusion of Other Embodiment>
3 and 4 show a screw having a heating zone modified from a torpedo.
The original purpose of a screw having a torpedo structure at its tip is to increase the degree of resin kneading by suppressing the amount of extruded resin and increasing the cylinder internal pressure (back pressure). For this reason, the screw outer diameter of this part may be taken larger than the outer diameter of the metering zone MZ. Even with the same outer diameter, the torpedo does not cut a screw groove or the like, so the forward thrust is small and the pressure is increased because it is difficult to push out.

The screw shown in FIGS. 3 and 4 is structurally similar to the screw with a torpedo structure, but the purpose and function are completely different. That is, the outer diameter of the torpedo of this screw is clearly smaller than the outer diameter of the metering zone MZ, but rather smaller than the inner diameter of the screw groove in the metering zone MZ. That is, when the inner diameter of the screw groove in the metering zone MZ is Dmb, the heating zone HZ is formed in a torpedo structure having an outer diameter of Dmb or less.
Because of this structure, back pressure does not increase due to the influence of this part. In this structure, the amount of the resin in the zone increases, and there is no structure for propelling forward. Therefore, the structure moves forward only by the pushing-out effect with the extruded resin from the rear, and as a result, the residence time increases. 3 and 4, the weir Q is provided at the connecting portion between the metering zone MZ and the heating zone HZ. With such a weir Q, the pressure to the metering zone MZ can be stabilized. Furthermore, the pressure can be adjusted by the hole diameter of the breaker plate installed at the tip of the cylinder.

  3 and 4, if at least one of a groove, a pin, and a stirring blade is provided in the heating zone HZ formed in the torpedo structure, the resin is stirred by these, so that the heating of the resin Efficiency can be increased and more uniform heating can be expected. That is, in the heating zone HZ having a torpedo structure, the resin is not kneaded, but the resin is agitated by rotating the screw, so that the resin agitation can be promoted while suppressing mixing.

<Molding method using an extruder equipped with a screw>
The above-described screw is used when a pattern coloring pigment master batch is dry blended to form an original pattern. In particular, it is used for an extruder screw for blow molding and extrusion molding in which the heat necessary for melting a pattern coloring pigment master batch and pattern coloring is insufficient with only a crosshead or an extrusion die. That is, the present screw is a screw that assists in raising the temperature of the extruded resin.

This screw is divided into at least 4 zones. It is necessary to set the temperature for each zone. Heating is controlled by detecting the cylinder surface from the outer surface of the cylinder containing the screw with a temperature sensor and heating it with a band heater or the like so that the deviation is minimized. In this screw, the setting reference is clearly different between the heater temperature setting up to the metering zone MZ and the heater temperature setting in the heating zone HZ.
That is, since the heater up to the metering zone MZ is for the purpose of plasticizing and kneading the molding material, it is a temperature condition necessary for plasticizing the molding material and kneading the molding material. The heating zone HZ is This is for setting a temperature condition necessary for melting and coloring the pattern coloring pigment master batch added to the molding material. Up to the metering zone MZ, the molding material is of course melted and heated until it has a certain fluidity. If the pattern coloring pigment masterbatch is melted under these conditions, it will be included in the masterbatch due to the screw kneading action. The pigment component to be dispersed is uniformly dispersed in the molding material and the pattern cannot be colored.

  For example, since polypropylene has a melting point of 160 ° C., an appropriate temperature condition of the metering zone MZ is approximately 200 ° C. plus about 40 ° C. Therefore, the melting point of the pattern coloring pigment master batch needs to be a material having a higher temperature. Preferably, a substance having a Vicat softening point close to this temperature is preferred. In the case of a pattern coloring pigment master batch based on such a substance, it is possible to prevent the pigment from being dispersed by the metering zone MZ.

  On the other hand, in the heating zone HZ, the temperature is set higher than the melting point of the pattern coloring pigment master batch. Preferably, it is melting | fusing point +10 degreeC or more of a pattern coloring pigment masterbatch. Under this temperature condition, if the kneading strength as in the metering zone MZ is kneaded, the pigment will naturally disperse. However, in the screw of this embodiment, the hot kneading strength of this zone is suppressed, so the pattern coloring pigment master Although the batch is melted and softened, the degree of dispersion of the pigment component in the master batch is suppressed and distributed in the molding material in a deformed state or a partially colored state. When reheated with a crosshead or a die in this state, the fluidity increases at once and a colored pattern appears on the surface of the extruded resin.

  The extruder equipped with this screw is particularly suitable for continuous blow molding and extrusion molding with a small die structure. The reason for this is that in an in-die accumulator blow molding machine with a large crosshead or an extrusion molding machine equipped with a large die, heating to the extent that the resin temperature is raised is possible after the extruder, but a small cross This is because a continuous blow molding machine using a head or an extrusion molding machine with a small die structure is difficult because the portion to be heated is small. For this reason, in a continuous blow molding machine or an extrusion molding machine with a small die structure, an extruder equipped with this screw is required. In particular, pattern coloring, which was difficult with a small die, can be patterned with an ordinary die without the need for a large die or complicated specifications.

  The extruder equipped with the present screw is effective and preferable even in the extrusion molding with an in-die accumulation type blow molding or a large die. This is because heating in the crosshead or die without diffusion flow can heat the surface of the extruded resin, but it is difficult to heat the inside. For this reason, it is difficult to stabilize the coloring conditions due to deterioration of moldability by heating more than necessary, insufficient melting of the pattern coloring pigment master batch due to insufficient heating, and pattern dispersion due to excessive heating. In this respect, if it is an extruder equipped with the present screw for extruding a uniformly heated resin up to the coloring condition temperature, the heating conditions in the crosshead and the die are relaxed and the pattern is stabilized.

  In addition, when shape | molding using the extruder equipped with this screw, since coloring conditions are generally prepared at the time of leaving an extruder, the heating after an extruder is not required so much. Rather, a heat retaining state is preferable. That is, it is not preferable that the temperature suitable for coloring is too high, so it is better not to heat the extruder after the extruder.

A series of pattern coloring pigment master batches shown in Japanese Patent Application Laid-Open Nos. 2001-294671 and 2003-238695, while exchanging 50 Millisk of JEB-7 hollow molding machine manufactured by Nippon Steel Co., Ltd. Molding was evaluated using a molding method.
As a wood grain appearance evaluation mold, an upper blow-in pencil-filling blow mold having an external dimension of 80 W × 210 L × 15 T and engraved so that a ballpoint pen, a pencil, and an eraser can be used was used.
As the molding material, a material obtained by dry blending 0.3 part of a wood grain pigment master batch and 2.0 parts of a base pigment master batch with respect to 100 parts by weight of the molding material was used.
Molding material: Idemitsu Petrochemical Co., Ltd. polypropylene E-150GK
-Wood pigment masterbatch: Brown-based wood color masterbatch described in JP-A-2003-238695-Base pigment masterbatch: LD beige pigment masterbatch PEX798369 manufactured by Tokyo Ink Co., Ltd.

<Comparative Example 1>
Using a JEB-7 standard screw shown in FIG. 5, molding was performed under the following conditions.
(Standard screw specifications)
・ Feed zone length: 6D
・ Compression zone length: 7D
-Metering zone length: 12D
・ Groove pitch to metering zone: 50mm (1D)
・ Feed zone groove depth: 9mm
・ Metering zone groove depth: 3.5mm
・ Maximum compression ratio (feed zone / metering zone): 2.3
・ L / D: 25

(Molding condition)
・ C1: 170 ℃
・ C2: 180 ℃
・ C3: 190 ℃
・ C4: 200 ℃
・ Adapter (joint) part: 210 ℃
・ Crosshead: 230 ℃
・ Parison extrusion lip die: 215 ℃
・ Screw rotation speed: 20-60rpm
・ Cooling time: 45 seconds (result)
At 20 rpm, it colored once, but when it exceeded this, it was extruded in a state of insufficient melting and the pattern became difficult to appear.

<Comparative example 2>
The molding conditions of Comparative Example 1 were changed as follows.
(Molding condition)
・ C1: 180 ℃
・ C2: 190 ℃
・ C3: 200 ℃
・ C4: 210 ° C
・ Adapter (joint) part: 220 ℃
・ Crosshead: 230 ℃
・ Parison extrusion lip die: 215 ℃
・ Screw rotation speed: 20-60rpm
・ Cooling time: 45 seconds (result)
At 20 rpm, the streaks extend and the pattern becomes unclear. At 30 to 40 rpm, the wood is colored, but when it exceeds this, it is extruded in a state of insufficient melting and the pattern becomes difficult to appear.

<Comparative Example 3>
The molding conditions of Comparative Example 1 were changed as follows.
(Molding condition)
・ C1: 180 ℃
・ C2: 190 ℃
・ C3: 200 ℃
・ C4: 220-230 ° C
・ Adapter (joint) part: 215 ℃
・ Crosshead: 215 ℃
・ Parison extrusion lip die: 215 ℃
・ Screw rotation speed: 20-80rpm
(result)
(i) When C4 was set to 220 ° C. and extruded, it was good at 20 rpm or less, but when it exceeded 20 rpm, the wood pigment masterbatch was observed to be insufficiently melted, and when it exceeded 30 rpm, it was completely melted and extruded. This made the pattern difficult to appear.
(ii) When C4 was set to 225 ° C. and extruded, the wood grain pattern was in a grid pattern and good at 20 to 30 rpm. When it exceeded 30 rpm, the lack of melting was observed when the wood pigment master batch was crushed, and when it exceeded 40 rpm, the wood pigment was in a dispersed state, but insufficient melting was also observed.
(iii) When C4 is set to 230 ° C. and extruded, the wood grain pigment is dispersed at 20 rpm, and the pattern becomes unclear. At 30 rpm or higher, the wood pigment disperses and the wood grain pattern does not appear.

<Example>
In the screw shown in FIG. 1, a 50 millisk screw having the following specifications was produced.
(Screw specifications)
・ Feed zone length: 6D
・ Compression zone length: 7D
-Metering zone length: 7D
・ Heating zone length: 5D
・ Groove pitch to metering zone: 50mm (1D)
・ Groove pitch of heating zone:
First groove pitch 0.8D, second groove pitch 0.65D,
0.5D after the third groove pitch
・ Feed zone groove depth: 9mm
・ Metering zone groove depth: 3.5mm
・ Groove depth of heating zone
5 mm between first groove pitches, 7 mm between second groove pitches,
10mm after the third groove pitch
・ Maximum compression ratio (feed zone / metering zone): 2.3
・ L / D: 25

(Molding condition)
・ C1: 180 ℃
・ C2: 190 ℃
・ C3: 200 ℃
・ C4: 220-230 ° C
・ Adapter (joint) part: 215 ℃
・ Crosshead: 215 ℃
・ Parison extrusion lip die: 215 ℃
・ Screw rotation speed: 20-80rpm
Cooling time: 45 seconds Here, C1 is a feed zone, C2 is a compression zone, C3 is a metering zone, and C4 is installed at a position substantially coincident with the heating zone.
(result)
(i) When C4 was set to 220 ° C. and extruded, it was good at 20 to 40 rpm or less, but when it exceeded 40 rpm, it was observed that the wood pigment masterbatch was insufficiently melted. The pattern was hard to come out.
(ii) When C4 was set to 225 ° C. and extruded, the wood grain pattern was in a grid pattern and was good at 20 to 60 rpm. When it exceeded 60 rpm, it was observed that the wood pigment masterbatch was insufficiently melted, and when it exceeded 80 rpm, it was completely melted and extruded, making it difficult to produce a pattern.
(iii) When C4 is set to 230 ° C. and extruded, at 20 to 30 rpm, the streaks extend and the pattern becomes unclear. At 30 to 70 rpm, the wood grain pattern was a fine streak pattern and was good. When it exceeded 70 rpm, the lack of melting in the state where the wood grain pigment masterbatch was crushed was observed.

  The resin extrusion screw and molding method of the present invention are suitable for patterns such as wood grain patterns, but can be used without problems for pattern coloring such as marble, stone, marble, etc. For low materials, etc., uniform heating and extrusion can be performed accurately below the decomposition temperature.

The figure which shows the screw for resin extrusion which concerns on embodiment of this invention. The figure which shows the screw for resin extrusion which concerns on the modification of embodiment same as the above. The figure which shows the screw for resin extrusion which concerns on other embodiment of this invention. The figure which shows the screw for resin extrusion which concerns on other embodiment of this invention. The figure which shows a standard screw.

Explanation of symbols

FZ ... feed zone,
CZ: Compression zone MZ: Metering zone
HZ ... heating zone

Claims (11)

  The resin extrusion screw having a feed zone, a compression zone, and a metering zone has a heating zone for heating the resin while suppressing mixing of the resin from the metering zone to the screw tip. Resin extrusion screw.   The screw for resin extrusion according to claim 1, wherein a screw groove is formed in the heating zone, and the screw groove in the heating zone has a groove pitch and a groove depth with respect to the screw groove in the metering zone. A screw for resin extrusion, wherein at least one of the two is formed to have different dimensions.   3. The resin extrusion screw according to claim 2, wherein the compression is obtained by dividing the groove volume between one groove pitch of the screw grooves in the feed zone by the groove volume between one groove pitch of the screw grooves in the metering zone. The ratio CRm and the compression ratio CRh obtained by dividing the groove volume between one groove pitch of the screw grooves in the feed zone by the groove volume between one groove pitch of the screw grooves in the heating zone are CRm> CRh A screw for resin extrusion characterized by the above.   The screw for resin extrusion according to claim 3, wherein at the boundary between the metering zone and the heating zone, the groove pitch is gradually decreased and the groove depth is gradually increased from the metering zone toward the heating zone. Thus, a screw for resin extrusion, wherein a screw groove is formed.   The screw for resin extrusion according to any one of claims 1 to 4, wherein the screw outer diameter Dh of the heating zone is smaller than the screw outer diameter Dm of the metering zone. Screw for use.   The screw for resin extrusion according to claim 1, wherein when the inner diameter of the screw groove of the metering zone is Dmb, the heating zone is formed in a torpedo structure having an outer diameter equal to or less than the Dmb. Characteristic screw for resin extrusion.   The screw for resin extrusion according to claim 1 or 6, wherein the heating zone is formed in a torpedo structure and at least one of a groove, a pin, and a stirring blade for increasing the heating efficiency of the resin. A screw for resin extrusion characterized by comprising:   The screw for resin extrusion according to any one of claims 1 to 7, wherein when the screw outer diameter of the metering zone is Dm and the effective screw length including the heating zone is L, L / Dm is A screw for resin extrusion, characterized in that it is 20 or more and the length of the heating zone is 2 Dm or more.   The screw for resin extrusion according to any one of claims 1 to 8, wherein the heating zone is configured to be exchangeable.   A molding method for blow-molding a pattern-colored product using the extruder equipped with the resin extrusion screw according to any one of claims 1 to 9, wherein the pattern-colored pigment master is used up to the metering zone. Heating at a temperature not exceeding the melting point of the batch, and heating in the heating zone above the melting point of the pattern coloring pigment master batch. A molding method for extruding a pattern-colored product using the extruder equipped with the resin extrusion screw according to any one of claims 1 to 9, wherein the patterning pigment master is used up to the metering zone. Heating at a temperature not exceeding the melting point of the batch, and heating in the heating zone above the melting point of the pattern coloring pigment master batch.

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