JP4478548B2 - Molding method of thermoplastic resin melt - Google Patents

Description

  The present invention relates to a method for removing and molding bubbles contained in a melt before supplying to a press mold when a thermoplastic resin melt is cold-pressed to obtain a molded product.

  Conventionally, as a method for obtaining a thermoplastic resin melt, one or more types of chip-shaped plastic materials obtained by pulverizing a plastic material made of the recovered thermoplastic resin with a pulverizer, waste paper, rubber waste, fiber, wood powder Dissimilar waste materials such as wood and wood, and dissimilar materials in the form of fine pieces and powders are supplied to the mixing machine. A method of melting and mixing a molten thermoplastic resin and a different material to form a molding material in a melt-mixed state is known. (For example, refer to Patent Document 1).

  In the above method, a predetermined amount of the molding material obtained in the melt mixed state is supplied into the molding die of the molding apparatus while maintaining the molten state, and the molding material is cooled and press-molded into a predetermined shape to obtain a molded product. . However, since the molding material melted by the above-mentioned method is obtained as a melt in a bulk state, it is difficult to divide and measure and a state in which a large amount of air bubbles are contained unevenly therein. Therefore, if a predetermined amount of molding material is supplied to the mold as it is and press-molded, the resulting molded product will have a large variation in weight and will contain voids in it. Causes a drop.

  Therefore, press molding is performed after removing air bubbles in the molding material as much as possible. Normally, deaeration in such a case is performed by filling the mold with the amount of molding material and lightly closing the mold. A method is employed in which the amount of material is heated until it is in a molten state, and then pressurization and depressurization of the molding die is repeated to degas. However, if a molded body is obtained by cold pressing the thermoplastic resin melt without performing hot pressing, if the degassing operation is performed in the molding die, the molding material is not removed during the degassing operation. It is necessary to heat the molding die so as to keep the molten state.

On the other hand, the molding material brought into the melt-mixed state in the mixing and melting step is measured and divided into a lump of a predetermined weight before being supplied to the molding die, and is supplied to the molding die. And when this measurement division operation is performed, it may happen that the molding material which has been in a melt-mixed state is cooled and becomes a solid state from a semi-solid state. Therefore, it is necessary to reheat the molding material supplied into the mold. In this case, the extraneous material in the molding material, in particular, wood powder or wood fragments, is further heated and carbonized, etc. There is a possibility that the molded product to be discolored or the strength is lowered. In addition, the molding die must be a heating die for remelting the molding material, and there is a problem that the die structure in the molding material is complicated and expensive.
JP-A-11-226956

  The present invention has been made for the purpose of providing a molding method of a thermoplastic resin melt that is easy and inexpensive and can be molded without deterioration and insufficient strength of a molded product to be obtained.

  Specifically, the operation atmosphere of the molding operation is maintained at a temperature at which the thermoplastic resin is kept in a molten state, and degassing is performed under the temperature atmosphere, and the resin melt is divided into chunks of a predetermined weight. The present invention provides a method for molding a thermoplastic resin melt that requires only one heating for melting the molding material and does not require the molding die to be a heating die.

  A thermoplastic resin melt molding method (Invention 1) according to claim 1 is a degassing apparatus comprising a plurality of pairs of rolls in which a thermoplastic resin melt supplied from a melting apparatus and containing bubbles therein is sequentially narrowed. The multi-stage rolling is performed, the internal bubbles are removed and the sheet is shaped into a sheet, and then the sheet-like thermoplastic resin melt is moved onto the weight measuring device, and the deaeration device and the weight measuring device are moved to a predetermined weight. When the thermoplastic resin melt is measured and divided by cutting with a cutting device provided between the two and put into a molding die and cooled by a press device to obtain a molded product, the thermoplastic resin is melted. The product is characterized in that it is in a molten state from the melter outlet to the presser inlet.

  The invention according to claim 2 (invention 2) was obtained by melting the thermoplastic resin with frictional heat generated by kneading the thermoplastic resin with blades rotating at high speed in the chamber. The method for molding a thermoplastic resin melt according to the first aspect of the present invention.

  The invention according to claim 3 (invention 3) is a group in which the thermoplastic resin melt is composed of 100 parts by weight of molten thermoplastic resin, and plant shredded pieces, shredded pieces, shredded pieces, plant fibers, and threshing residues. The method for molding a thermoplastic resin melt according to Invention 1 or 2, wherein 50 to 200 parts by weight of at least one substance selected from the above is mixed.

  The invention according to claim 4 (invention 4) is the molding of the thermoplastic resin melt according to any one of inventions 1 to 3, wherein the thermoplastic resin melt comprises a plurality of thermoplastic resins having different melting temperatures. Is the method.

  The thermoplastic resin in Invention 1 is not particularly limited as long as it is a general thermoplastic resin. For example, as an example, PE (polyethylene), PP (polypropylene), PVC (vinyl chloride resin), PET (polyethylene terephthalate), PSt ( Polystyrene), ABS (acrylonitrile styrene butadiene copolymer resin), AS (acrylonitrile styrene copolymer resin), AES (acrylonitrile-ethylene propylene diene terpolymer-styrene copolymer resin), PMMA (polymethyl methacrylate), polyamide, polycarbonate, methacryl Resins, polyurethane, polyvinyl acetate and the like can be mentioned.

  This resin is in a state of containing bubbles when it is in a molten state. That is, if these resin raw materials contain air between materials such as powder or pellets, they are melted by a general kneading melter such as an extruder to melt the raw materials. In this case, most of the air contained in the raw material is removed by the pressure during kneading and melting, but a part of the air remains in the molten raw material.

  Also, like the melt mixer described in Patent Document 1, the raw material thermoplastic resin is put into the chamber, the stirring blade is rotated at high speed and stirred, and the thermoplastic resin is melted by internal friction heat to be melted. In the method using the molding material, a large amount of air remains in the melt.

  If the resin in this state is press-molded as it is, residual air remains as voids and nests in the molded product, and the strength of the molded product decreases and the appearance deteriorates. Therefore, when this is press-molded, it must be deaerated beforehand. According to the degassing method of the present invention, a thermoplastic resin melt containing air is sequentially passed between a plurality of roll pairs in which the surface intervals of the roll pairs are sequentially narrowed, and the thermoplastic resin melt is made into a roll pair. Multi-stage degassing is performed by a degassing device that degass by alternately applying compression and depressurization until reaching the next roll pair from the roll pair.

  Since this deaeration device is composed of a plurality of pairs of rolls, the molten thermoplastic resin is simultaneously rolled. Therefore, the molten thermoplastic resin melt that has come out of the last roll pair comes out in a state of being completely deaerated and shaped into a sheet shape having a predetermined thickness. In addition, when batch-type melt kneading as in Invention 2 is performed, a sheet-like melt can be continuously obtained by optimizing the timing of batch-type melting and using the measurement division method of the present invention. The timing adjustment between the melt kneading and the cooling press molding in the next step becomes easy.

  In order to prevent the thermoplastic resin melt compressed by the roll pair from spreading laterally, a weir plate, guide plate or guide roll having a predetermined width is placed between the faces of the opposing roll pair or between the roll pair and the next roll pair. It is preferable that the movement of the thermoplastic resin in the width direction is restricted.

  In addition, since the roll pair only needs to exhibit the effect of degassing the thermoplastic resin melt and shaping it into a sheet shape, one roll may be used as a conveyor instead of the roll pair. If so, the degassed thermoplastic resin melt can be moved more smoothly.

  In addition, although the thickness width of a sheet-like melt is not specifically limited, 3-10 cm is preferable for shaping | molding at the next process. When wood powder or the like is added, carbonization of the wood powder due to internal heat generation can be prevented by setting the thickness to 7 cm or less.

  Next, the degassed sheet-shaped thermoplastic resin melt is moved onto a weight measuring device. The weight measuring device may be a general weighing conveyor equipped with a weight sensor provided after the deaeration device. A cutting device is provided between the deaeration device and the weight measurement device. This cutting device has a function of cutting the thermoplastic resin melt continuously coming out from the last roll pair of the degassing device by the signal when a predetermined weight of the thermoplastic resin melt is detected by the weight measuring device. Have

  At the time of cutting, the thermoplastic resin melt that has moved is temporarily stopped, and the melt is cut by a cutting device provided between the roll pair of the degassing device and the weighing conveyor. The cutting is usually performed by shear cutting by shearing or the like.

  The cut thermoplastic resin melt is finally weighed by a weight-measuring device and supplied to a molding die as the next step. Since the thermoplastic resin melt moves from the deaerator as a continuous body, the measured value at the time of cutting is set based on the weight of the thermoplastic resin melt after actual cutting. It is preferable to sequentially measure the weight of the thermoplastic resin melt after cutting and feed it back to the measured value at the time of cutting the next lot.

  Therefore, it is necessary that the thermoplastic resin melt leaving the weight measuring device and supplied to the molding die is in a state of being surely melted. For this reason, in the present invention, the thermoplastic predicate melt It is preferable that the temperature and the atmospheric temperature of the apparatus in contact with are heated to the melting temperature or higher of the thermoplastic resin.

  That is, at least from the degassing device inlet to the weight measuring device outlet, it is necessary that the thermoplastic resin melt is kept in a molten state all the time. For example, the roll of the degassing device is a heating roll. The weight measuring device is preferably a heated conveyor. Furthermore, it is better that a heat insulating cover or the like is provided to cover the entire process. In addition, a heating roll or a heating conveyor should just be heated by arbitrary heat sources, such as electric heating, oil heating, or steam heating, and is not specifically limited.

  The thermoplastic resin melt cut to a constant weight is supplied into the mold while maintaining the molten state, and since deaeration has already been completed, the desired molded body can be obtained simply by cooling and pressing as it is. .

  Invention 2 is obtained by melting a thermoplastic resin with frictional heat generated by kneading the thermoplastic resin with blades rotating at high speed in a chamber. That is, in Invention 2, the thermoplastic resin containing bubbles inside is melted by the same method as the technique described in Patent Document 1.

  Therefore, since the thermoplastic resin melt obtained by this method contains a large amount of air, the degassing method according to claim 1 can be effectively applied.

  In invention 3, the thermoplastic resin melt is at least one substance 50 selected from the group consisting of 100 parts by weight of molten thermoplastic resin, and plant shredded pieces, shredded pieces, cut pieces, plant fibers, and threshing residues. -200 weight part is mixed.

  By adding plant pieces to the thermoplastic resin, the effect of reinforcing the resin by the plant pieces can be obtained, and the strength of the resulting molded product can be increased and wood texture can be obtained. If the plant piece is 10 parts or less, both effects are insufficient, and if it exceeds 200 parts, kneading becomes difficult.

  If the thermoplastic resin is melted in an open state as in Invention 2, moisture contained in plant pieces such as wood or bamboo pulverized or cut bodies is converted into water vapor by heat at the time of melting and easily released into the atmosphere. It is. Even if moisture remains, it is reliably removed as water vapor in the deaeration process, so that it is not necessary to dry the plant pieces in advance.

  If the obtained thermoplastic resin melt is left in a lump shape, dehydration of the plant pieces proceeds inside the lump shape, and the internal temperature of the thermoplastic resin melt rises due to heat generation, and carbonization occurs. By forming the sheet in a street shape, it becomes difficult for heat generation to proceed and carbonization can be suppressed.

  In the invention 4, the thermoplastic resin melt is composed of a blend of a plurality of thermoplastic resins having different melting temperatures, for example, PE (polyethylene) and PP (polypropylene). These resins may be recycled materials as well as virgin materials.

  When the thermoplastic resin is melted by frictional heat due to the collision of the thermoplastic resin as in the invention 2, a plurality of resins having different melting temperatures are simultaneously put into the chamber, and the rotating blades are rotated at a high speed to generate heat. When melting the plastic resin, the unmelted thermoplastic resin preferentially generates heat. Therefore, it becomes difficult for the thermoplastic resin having a low melting temperature to be thermally decomposed as compared with the external superheating type melting method. Therefore, the obtained molded product has little discoloration and is difficult to decrease in strength.

  Furthermore, blending of thermoplastic resins having different melting temperatures and kneading of plant fillers containing moisture can be facilitated, but the thermoplastic resin melt mixed with the obtained filler has a large amount of uneven bubbles. It becomes a lump containing. Therefore, it is preferable to apply the method of the invention 1 to the deaeration and measurement.

  In the invention 1, the process from the melting apparatus to the press molding apparatus is maintained at a temperature at which the resin melt is maintained in a molten state, and the thermoplastic resin melt supplied from the melting apparatus is removed under the temperature atmosphere. Since the gas and the sheet are formed and the resin melt is divided into a lump of a predetermined weight, the divided melt has a constant weight and does not contain air. Therefore, it only needs to be heated once to melt the molding material, and there is no need to use a molding die as a heating die, so there is no deterioration or insufficient strength of the resulting molded product, and it is easy and inexpensive to press. It becomes the molding method of the thermoplastic resin melt which can be molded.

  Furthermore, the deaeration process is a method of repeatedly pressing and depressurizing the molten resin by passing between a plurality of facing roll pairs, and the thermoplastic resin melted by the roll pairs is rolled into a sheet. Therefore, it is difficult for heat to remain in the sheet, and it is possible to reliably perform the cutting operation after the measurement in the next process.

  In invention 2, since the thermoplastic resin melt is obtained by melting the thermoplastic resin with frictional heat generated by kneading the thermoplastic resin with blades rotating at high speed in the chamber, Contains a large amount of air. Therefore, the metering step of the thermoplastic resin melt of the invention 1 is preferably applied.

  In invention 3, the thermoplastic resin melt is at least one substance selected from the group consisting of 100 parts by weight of molten thermoplastic resin, and plant crushed pieces, crushed pieces, cut pieces, plant fibers, and threshing residues. Since 50 to 200 parts by weight are mixed, the molten thermoplastic resin contains water derived from the plant material as water vapor. Therefore, since many bubbles are contained, the metering and dividing step of the thermoplastic resin melt of the invention 1 is suitably applied.

  In invention 4, the thermoplastic resin melt is composed of a blend of a plurality of thermoplastic resins having different melting temperatures.

  Since the thermoplastic resin is a plurality of resins having different melting temperatures, when these thermoplastic resins are put into the chamber at the same time and the rotating blade is rotated at a high speed to melt the thermoplastic resin, the heat in the actual molten state is obtained. The plastic resin generates heat preferentially, and the thermoplastic resin having a low melting temperature is difficult to be thermally decomposed. Therefore, the molded product obtained has little discoloration and is difficult to decrease in strength.

  Next, the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view for explaining the function of an example of a part of an apparatus for carrying out the method for measuring and dividing a thermoplastic resin melt according to the first aspect of the present invention. FIG. 2 is a cross-sectional view showing the operation principle of an example of a thermoplastic resin melt mixing apparatus. FIG. 3 is a plan view of an example of a regulator that prevents the resin melt from spreading in the width direction. FIG. 4 is a procedure diagram showing an example of a part of the procedure for degassing and metering the thermoplastic resin melt.

  As shown in FIG. 1, the thermoplastic resin P is melted in the melt mixing device 1 and continuously supplied to the deaeration device 2. As an example of the melt mixing apparatus 1, as shown in FIG. 2, for example, a thermoplastic resin P is put into a hopper 14 of the melt mixer 1, and a screw 13 that rotates a predetermined amount of the thermoplastic resin P with an electric motor or the like. To the chamber 12. A plurality of stirring blades 121 for agitating the thermoplastic resin and melting the thermoplastic resin by frictional heat generated at that time are provided in the chamber 12.

  A gap is provided between the stirring blade 121 and the inner wall of the chamber 12 in order to smoothly rotate the stirring blade 121. The thermoplastic resin P put into the chamber 12 is melted by frictional heat, and becomes a thermoplastic resin melt P containing bubbles inside.

  As in Invention 2, the thermoplastic resin melt P was obtained by causing the thermoplastic resin P to collide with the stirring blade 121 rotating at a high speed in the chamber 12 and melting the thermoplastic resin P with the generated frictional heat. If it is a thing, the melt P will contain a large amount of air.

  As in the invention 3, if the thermoplastic resin melt P is obtained by mixing 100 parts by weight of the melted thermoplastic resin with 50 to 200 parts by weight of a pulverized plant piece such as wood or bamboo, or a cutting body, The melted and mixed thermoplastic resin melt P contains moisture derived from the plant pieces as water vapor. Accordingly, more bubbles are contained in the melt P, but the above melt mixing method is performed in an open form, so that water vapor easily escapes, and it is not necessary to dry the plant pieces in advance.

  The melted thermoplastic resin melt P is sequentially discharged from the outlet 15 of the melt mixer 1 and sent to the degassing device 2 comprising a plurality of pairs of rolls 21, 22,. It is done. In the deaeration device 2, a plurality of roll pairs 21, 22,... Are arranged in order so that the thermoplastic resin melt P is rolled while passing between the surfaces of each roll pair. Therefore, the thermoplastic resin melt P is compressed by each pair of rolls 21, 22,..., And is compressed between leaving the roll (for example, 21) and reaching the next roll (for example, 22). It is released and compressed again with the next roll (for example 22), thus repeatedly undergoing compression and decompression. Accordingly, bubbles contained in the melt P are removed, that is, degassed.

  The distance between the surfaces of each pair of rolls 21, 22,. Therefore, when passing between the first roll pair 21 containing a large amount of bubbles, the thermoplastic resin melt P is not compressed so strongly, but many bubbles are lost and the last roll pair is reduced. In the case of passing, it will be subjected to fairly strong compression and the bubbles will be completely degassed.

  In this way, the thermoplastic resin melt P deaerated in multiple stages by each of the roll pairs 21, 22,... Is simultaneously rolled between the roll surfaces and spread in the lateral direction. Therefore, as shown in FIG. 3, guide plates 221, 222,... For preventing lateral expansion are provided between the roll pairs 21, 22,. It is better to prevent the spread. In place of the illustrated guide plate, a dam plate or a guide roll having a predetermined width is inserted between the faces of the opposing roll pair or between the roll pair and the next roll pair (both not shown). Thus, the spread in the width direction of the thermoplastic resin melt P may be regulated.

  Moreover, since the roll pairs 21, 22,... Need only exhibit the effect of degassing the thermoplastic resin melt P and shaping it into a sheet shape, for example, as shown in FIG. A pair of rolls may be brought close to the rolls via the conveyor 221. In this case, the degassed thermoplastic resin melt P can be moved more smoothly.

  The thermoplastic resin melt P, from which internal bubbles are removed by each roll and subjected to multi-stage rolling, is shaped into a sheet and is placed on the weight measuring device 4 (in this example, a normal weighing conveyor). Moved to. The sheet-shaped thermoplastic resin melt transferred onto the weighing conveyor 4 is cut at a predetermined weight by a cutting device 3 provided between the rolling device 2 and the weight measuring device 4.

  As the cutting device 3 for the thermoplastic resin melt P, a shear cutting device such as shearing is usually used. The melt P before cutting is a continuous body, and the movement of the melt P is temporarily stopped at the time of cutting. However, when the cutting device is moving in synchronization with the weighing conveyor, it is not always necessary to stop. At this time, it is preferable to feed back the last measured value in order to calculate and confirm the measured value at the time of cutting the next lot.

  The thermoplastic resin melt P after being cut is supplied to the molding die 5 and has already been deaerated and is in a molten state, and is thus pressed as it is. The molding die 5 does not need to be heated. Therefore, the thermoplastic resin melt P is maintained in a molten state in all the steps from immediately after leaving the melt mixing apparatus 1 to being supplied to the molding die 5. In the case of this example, the roll of the deaeration device 2 is an electric heating roll, and the weight measuring device 4 is a weighing conveyor incorporating an electric heater. Furthermore, a heat insulating cover (not shown) or the like may be provided to cover all the steps from the melt mixing apparatus 1 to the molding die 5.

  Next, a specific procedure for degassing and metering the thermoplastic resin melt P will be described with reference to FIG. First, the thermoplastic resin melt P melted by the melt mixing device 1 is supplied to the first roll pair 21 of the degassing device 1 (FIG. 4A). Next, as the conveyor 211 moves, the melt P sequentially passes through each pair of rolls 21, 22,..., And is degassed by roll compression and shaped into a sheet (FIG. 4B). ).

  The melt P that has been degassed is supplied to the weighing conveyor 4 and continuously weighed (FIG. 4C). When the weight reaches a predetermined weight, the belt conveyor 211 is stopped, and the thermoplastic resin melt P is cut and divided by the shearing cutting device 3 provided between the deaeration device 2 and the weighing conveyor 4 (FIG. 4D). ).

  The exit-side shutter 41 of the weighing conveyor 4 is opened, the cut melt P is taken out and supplied to the molding die 5 (FIG. 4 (e)). When the divided melt P disappears from the weighing conveyor 4, the next melt P has been supplied to the inlet side of the weighing conveyor 3, and the next weight measurement starts (FIG. 4 (f)). This is repeated thereafter.

It is a side view which shows the function of a part of example of the apparatus which enforces the molding method of the thermoplastic resin melt of the invention 1. It is sectional drawing which shows the principle of operation of an example of the melt mixing apparatus of a thermoplastic resin. It is a top view of an example of the control tool which prevents the resin melt from spreading in the width direction. It is a procedure figure which shows an example of a part of operation | work procedure of shaping | molding of a thermoplastic resin melt.

Explanation of symbols

P Thermoplastic resin melt (melt)
DESCRIPTION OF SYMBOLS 1 Melt mixing apparatus 12 Chamber 121 Stirring blade 13 Screw 14 Hopper 15 Outlet 2 Deaeration device 21,22, ... Roll pair 211 Belt conveyors 221, 222, ... Guide plate 3 Cutting device 4 Weight measuring device (weighing conveyor)
41 Exit side shutter 5 Mold

Claims (4)

The thermoplastic resin melt that is supplied from the melting device and contains bubbles is subjected to multi-stage rolling by a degassing device consisting of a plurality of pairs of rolls that are sequentially narrowed to remove the internal bubbles and apply it to a sheet. After forming, the sheet-like thermoplastic resin melt is moved onto a weight measuring device, and the thermoplastic resin is melted by cutting with a cutting device provided between the deaeration device and the weight measuring device at a predetermined weight. When a product is measured and divided, and this is put into a molding die and cooled by a press device to obtain a molded body,
A method for molding a thermoplastic resin molded article , wherein the thermoplastic resin melt is kept in a molten state from the melter outlet to the presser inlet. The thermoplastic resin melt is obtained by melting the thermoplastic resin with frictional heat generated by kneading the thermoplastic resin with blades rotating at high speed in the chamber. A method for molding a thermoplastic resin molded body . The thermoplastic resin melt is 50 to 200 parts by weight of at least one substance selected from the group consisting of 100 parts by weight of a melted thermoplastic resin and plant crushed pieces, pulverized pieces, cutting pieces, plant fibers, and threshing residues. The method for molding a thermoplastic resin molded article according to claim 1 or 2, wherein the thermoplastic resin molded article is mixed. The method for molding a thermoplastic resin molded article according to any one of claims 1 to 3, wherein the thermoplastic resin melt comprises a plurality of thermoplastic resins having different melting temperatures.

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