Patent Publication Number: US-5026512-A

Title: Method for manufacturing molded products of thermoplastic and inorganic materials

Description:
This is a continuation of application Ser. No. 051,738, filed May 18, 1987, U.S. Pat. No. 4,863,652, which is a continuation of Ser. No. 636,079, filed Jul. 31, 1984, U.S. Pat. No. 4,670,203, which is a continuation of Ser. No. 321,535, filed Nov. 16, 1981, abandoned, which is a continuation of Ser. No. 715,348, filed Aug. 17, 1976, abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a method for manufacturing molded products of polyethylene terephthalate (hereinafter referred to as PET) which are tough and have the characteristics required for the applications of the molded products, by using the PET, PET containing less than 20% of the isomer or PET blended with other polymers and/or inorganic fillers as a molding material. 
     Since the PET has highly useful characteristics, tough and durable products can be obtained by making fibers and films through extrusion, drawing and heat treatment by appropriate machines. Thus, when the PET is used as the fibers or films, it is drawn and can be heat-treated with the property of orientation given in the manufacturing processes of fibers or films, and the products will therefore be so tough as to exhibit fully the characteristics of PET. 
     Even if the molded products of the PET are manufactured by known methods with ordinary injection molding machines or extrusion molding machines, the products obtained cannot be drawn, and the PET is subject to hydrolysis and thermal deterioration due to oxidation during molding, slow in the crystallization and inferior in moldability. Therefore the PET products obtained by injection molding or extrusion molding are not as tough as the PET fibers, the PET films are extremely brittle with a variation of quality, and it is difficult to obtain excellent molded products of PET. Accordingly, in the conventional molding of the PET, the products are reinforced with glass fiber, a stabilizing agent is used to prevent qualitative deterioration and it is necessary to use a material of large molecular weight 18,000 to 30,000. Despite, the above-mentioned defects such as difficulty in obtaining tough high quality products, proneness to occurrence of incomplete molded products and necessity of expensive materials are not yet eliminated. Moreover, in conventional injection molding and extrusion molding of the PET, it has been considered difficult to use scraps and wastes of the PET and to mold the PET which was blended with various kinds of polymers or inorganic fillers. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a method for molding the PET which may be blended with other polymers or inorganic fillers as required in molding of the PET in order to prevent thermal deterioration and to control crystallization of the PET even when scraps and wastes of the PET are used, thus manufacturing excellent molded products of the PET. The control of crystallization of the PET is fulfilled by effectively utilizing the characteristic of the PET that, for example, the second-order transition point (glass transition point) of the PET is approximately 67° to 81° C., the velocity of crystallization is extremely low at 120° C. or less and is quicker at 120° to 190° C. in response to the degree of temperature, and crystals gradually disappear at approximately 255° to 265° C. and completely vanish at approximately 290° C. The crystallinity (degree and velocity of crystallization and size of crystal) of the PET is controlled by appropriately setting and controlling the pretreatment conditions (drying) of material, temperatures of injection molding or extrusion molding and temperatures of the molds and cooling water through the molds and performing the cooling and solidification of the PET uniformly and quickly. Through these processes and operations, tough and highly heat resistant products can be molded. 
     The present invention permits molding of excellent products with different characteristics, using the PET which is blended appropriately with one or more than two kinds of other polymers and inorganic fillers as required to make control of the crystallinity of the PET easier. 
     In other words the present invention provides a method for manufacturing molded products of the PET by molding a material containing the PET as a principal component characterized by using the dry virgin and/or waste PET of average molecular weight more than 10,000 as a material and molding said material under the following molding conditions: 
     (a) control of a temperature of a cylinder of a molding machine within the range of melting temperature ±35° C. of resins, and 
     (b) control of the staying time of resins in the cylinder to be within 15 minutes. 
     Other objects and features of the present invention will be known from the following descriptions. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view illustrating a fragmentary portion of a conventional molding machines, 
     FIG. 2 is a sectional view illustrating a fragmentary portion of the molding machine useful for the present invention, and 
     FIGS. 3 and 4 are a sketch of a hopper illustrating other examples of the molding machine useful for the present invention, respectively. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following describes in detail the present invention. 
     The present invention uses polyethylene terephthalate as a saturated polyester. Polyethylene terephthalate (PET) referred to in the present invention contains more than 80% of polyethylene terephthalate which is polymerized by reacting terephthalic acid or dimethylterephthalate (DMT) with ethylene glycol the polyethylene terephthalate containing, less than 20% of isomer or similar polyester, or the like. 
     The PET useful for the present invention can be available in the form of chips or pellets of virgin material for fibers and films. Moreover, pulverized waste PET, i.e., pulverized scraps and waste molded products of the PET or chips and pellets obtained by reproducing the waste PET can also be used. Virgin material, scraps and waste molded products can be used individually or simultaneously. The average molecular weight of the PET can be more than 10,000 and is preferably approximately 20,000. Though PET of large molecular weight more than 30,000 can be used, highly tough molded products cannot be obtained from PET of molecular weight less than 10,000. In case of using scraps and waste molded products of the PET, the stabilizing agents pigment, aggregate, catalysts, flame retarder etc. contained in these scraps and waste molded products scarcely affect the molding but they are preferably used so that the quantity of the scraps and waste molded products of the PET is less than 50 weight % of the total weight of each molded product. When the pulverized waste PET is used, the PET pellets of preferably more than 10 weight %, further preferably more than 30 weight %, or the pellets or fiber of other polymer of less than 60 weight % or the powdery granules or fiber of inorganic material of less than 60 weight % in reference to the total weight of molded products are blended in the pulverized PET to smooth feeding of the pulverized PET into the screw of the molding machine. When the pulverized particles of scraps are used as the PET material at the blended ratio of less than 50 weight % for a virgin material, the molded products can be inexpensively manufactured and glass fiber or inorganic powder can be mixed satisfactorily. 
     The water content in the PET is preferably less. If the PET contains a considerable amount of water, it will accelerate hydrolysis of molten PET in molding, cause thermal deterioration of the quality and produce brittleness. Therefore, the PET should be treated in advance by drying to reduce the water content of the PET to less than 1 weight %. In this case, the preferable range of water content in the PET can be 1 weight % for molding by means of the vent type extrusion molding machine with a vacuum pump but it is preferably 0.5 weight % for molding by means of the vent type injection molding machine with a vacuum pump. When such vent type molding machine with the vacuum pump is not used, it is more preferable to reduce the water content to 0.1 weight % or less and the most preferable range of the water content is less than 0.03 weight %. The drying treatment to reduce the water content in the PET to 0.1 weight % or less is generally performed for 3 to 6 hours at 110° to 150° C. This drying process serves to control the degree of crystallization of the PET in the final molded products in addition to reduction or removal of the water content in the PET. In other words, for the purposes of reducing the degree of crystallization of the PET and manufacturing the final molded products with excellent toughness, the PET material is dried at a lower temperature for a long period of time, for example, at 110° to 120° C. for 5 to 8 hours and, for the purposes of increasing the degree of crystallization and manufacturing the final molded products with excellent heat resistance, the PET material is dried at a higher temperature for a short period of time, for example, at 130° to 150° C. for 3 to 5 hours. In case a vacuum drying method is used for drying the PET, it is performed, for example, at 105°  to 130° C. for 1 to 4 hours under the reduced pressure of less than 50 mm Hg. The drying by means of the infra-red ray is satisfactory within one hour at 115° to 130° C. 
     As the molding material, the PET can be independently used and the PET blended with other polymer or inorganic material can also be used. The melting point of the PET is lowered by mixing the other polymer with the PET and therefore the molding of the PET can be performed by lowering the melting point of the PET and preventing thermal deterioration of the quality. 
     The polymers blended with the PET are polyolefin, such as polyethylene and polypropylene, polystyrene, acrylonitrile-butadienestyrene copolymer (ABS resin), polybutyleneterephthalate and polyamide such as nylon 6, nylon 66, nylon 8, nylon 12, nylon 7 and nylon 11, and cotton, rayon, hemp etc. can be blended. These polymers are individually blended with the PET or more than two kinds of the polymers are blended with the PET. The blending quantity of the polymers is preferably less than 60 weight % of the total weight of the molded product, and the more preferable range of the blending quantity is 5 to 40 weight % for polyolefin and polystyrene, 5 to 30 weight % for ABS resin, 5 to 40 weight % for polybutylene terephthalate, 5 to 50 weight % for polyamide and 5 to 30 weight % for cotton, rayon and hemp. The total blending quantity of more than two kinds of the above-mentioned polymers should be less than 60 weight %, preferably less than  50 weight %. For example, polyamide is 10 to 50% and polyethylene is 5 to 30%, polyamide is 10 to 50% and polybutylene terephthalate is 5 to 20%, and polyethylene is 10 to 30% and polypropyrene is 5 to 20%. Though the polymers can be blended with the PET, exceeding the blending quantities shown above, the blending quantity should be, in this case, limited to the values shown above since the characteristics of the PET in the final molded product will be reduce. Chips of a virgin material and scraps or wastes can be used as the polymers. The blending quantity of these scraps and wastes of the polymer is preferably less than 20 weight % of the total weight of the molded products. The water content of the polymers should be adjusted as in case of the PET. 
     Moreover, inorganic fillers can be blended with the PET or the PET blended with the other polymer at the rate of less than 60 weight % of the molded product. The inorganic fillers should excel in dispersibility when mixed in the PET and should not show disadvantageous chemical reaction with the PET and should preferably not have hygroscopic property. For example, the PET is blended with less than 5 weight % of boron nitride (BN) (in reference to the molded product; the same applied to the rest) less than 45 weight % of glass fiber, less than 35 weight % of glass balls and glass powder, less than 40 weight % of powders of feldspar, quartz, carbon, aluminium oxide, ceramic and marble, or less than 60 weight % of metallic powder, fiber and whisker such as iron, aluminium, copper, molybdenum, antimony, tungsten and boron. The above-mentioned inorganic fillers can be individually blended or more than two kinds of inorganic substances can be blended with the PET. Such selection is determined in accordance with the characteristics of the final molded products. In case of blending more than two kinds of said inorganic fillers or the inorganic fillers and other polymer with the PET, the total blending quantity is less than 60 weight %, preferably less than 50 weight %. In case of the powders of said inorganic fillers, the grain size of the powder particles can be approximately 100 mesh and is preferably smaller than 250 mesh or finer than 50 microns. When the inorganic fillers which are surface-treated are used as required, a more favorable product is obtained. Even though the blending quantity of inorganic filler is relatively small, the inorganic filler can be well mixed in pulverized particles of the waste PET and the pulverized particles of the waste PET can be easily fed to entangle with the screw of the molding machine. For example, boron nitride though its blending quantity of more than 0.03 weight % can be favorably mixed with said pulverized particles of the PET and the mixture can be molded by feeding the pulverized particles of the PET to the screw of the molding machine. 
     A pigment, dyestuff, surface treating agent, flame retarder etc. can be added as required in addition to said polymer and inorganic fillers. 
     Instead of mixing the PET with a polymer and an inorganic filler at the time of molding, virgin PET and PET wastes of average molecular weight of more than 10,000 are blended with at least one of the other polymer and/or the inorganic filler of 0.5 to 60 weight %, the blended substance is extrusion-molded by the vent type extrusion molding machine with vacuum pump under the pressure reduced to less than 100 mm Hg, preferably 50 mm Hg and further preferably 20 mm Hg and PET materials such as chips and pellets for molding which are cut in appropriate sizes and shapes can be manufactured and used for the molding material. In this case, the PET prepared by reacting and polymerizing terephthalic acid or dimethylterephthalate with ethyleneglycol in a molten state shortly before molding chips and pellets for fibers and films can be used. When this polymerization is almost finished or immediately after completion of the polymerization, said other polymer and/or inorganic filler are blended in the PET in the polymerizing oven with the pressure of less than 50 mm Hg and the PET mixture is extruded in desired shapes for the molding material after thorough mixing in the polymerizing oven. In this case, the other polymer and inorganic filler to be blended should not be decomposed or deteriorated and should have excellent heat resistance. 
     The following describes the manufacturing method for molded PET products using said molding materials. The molding machine to be used is preferably an injection molding machine in which the temperature can be well controlled or a vent type injection molding machine with vacuum pump. In selection of the injection molding machine, it is important to select a screw type injection molding machine with distinguished dispersibility or an effectively degassing type molding machine, in addition to excellence in temperature control. Thus, the molded PET products will be free from thermal deterioration and easy in control of crystallinity, and stable and excellent products can be obtained. Though a general type extrusion molding machine can be used for extrusion molding, it is preferable to use the vent type injection molding machine with vacuum pump. 
     The above specified material is fed into the injection or extrusion molding machine through its hopper. In this case, a humidity preventing apparatus such as, for example, a hopper drier should be preferably provided to protect the material to be fed from the humidity since thermal deterioration in heating the resin material can be prevented. Resin material supplied through this hopper are heated and melted in the cylinder of said molding machine. The heating temperature for the resin materials differs with the kinds and quantities of other components to be blended with the PET and the residence time of resins in the molding machine and should be the lowest temperature, at which the resins are melted, plus/minus 35° C. In other words, the temperature in the heating cylinder should be as low as possible to prevent hydrolysis and thermal deterioration from taking place. In this case, the heating temperature is preferably the resin melting temperature plus/minus 25° C. for injection molding and the resin melting temperature plus/minus 35° C. for extrusion molding. The preferable range of said heating temperature is 265° to 290° C. for the PET alone, 240° to 280° C. for the PET blended with polyethylene, a temperature lower than the above for the PET blended with polyamide and 265° to 300° C. for PET blended with the inorganic substance. However, the preferable heating temperature is generally below 275° C. in order to prevent thermal deterioration. 
     In molding, it is preferable to measure the temperature of resin by a surface temperature gauge or a thermocouple when the resin passes through the injection nozzle of the injection molding machine or the die or the adapter of the extrusion molding machine. Since the actual temperature of the molten PET can be measured as described above, the information is fed back and the heating of the cylinder is adjusted to appropriately control the internal temperature of the cylinder of the molding machine for control of crystallinity, size of crystal and condition of crystallization of the PET to fill the requirements for the characteristics of the final molded products, and the molding temperature can be set to a specified temperature. In other words, it is preferable that a temperature detecting section is provided in the resin passage in the molding machine to directly measure the temperature of resin shortly before injection or extrusion, the molding conditions are controlled mechanically in accordance with this measured temperature of resin and the variation of temperature when the resin is injected or extruded from the nozzle of the molding machine is maintained to be 3° C. higher and lower than the set temperature so that the resin may be molded in the optimum range of molding temperature. 
     Since the materials should be fully kneaded, it is preferable to select a screw with suitable shape of the threaded part and pitch and to provide a special nozzle in the molding machine. The materials are fully kneaded and dispersed and are molded in the specified shape within 15 minutes, preferably 5 minutes and further preferably 3 minutes of the staying time in the cylinder. If the resin stays in the cylinder for an excessively long period of time, the PET deteriorates, the strength of the molded product reduces and the molded products become so brittle as to be easily broken, and therefore the residence time should be as short as possible. Particularly, when the heating temperature for resins is high, the residence time of resins in the cylinder should be reduced. 
     For manufacturing the injection or extrusion molded products, the vent type injection or extrusion molding machine with a vacuum pump is used as the molding machine and the pressure in the molding machine is reduced by the vacuum pump through the vent to less than 150 mm Hg, preferably to less than 100 mm Hg and further preferably to less than 50 mm Hg and the water content and oxygen in the material are removed. Accordingly, the preliminary drying treatment of the material can be omitted or simplified, hydrolysis and thermal deterioration of the PET can be prevented, the temperature in the cylinder can be slightly raised from usual, the staying or residence time of the resin in the cylinder can be approximately 15 minutes, molding of large size products and thick wall products is facilitated and production can be increased. When the vent is provided at a position where the temperature of material rises up to 120° to 150° C., that is, at a position as long as 1/3 of the overall length of the cylinder of the molding machine away from the hopper, the water content in the material is apt to be effectively removed. If a gas hole, for example, is provided at a lower part of the hopper of the molding machine and dry nitrogen gas is supplied from the lower part to the upper part of the hopper through this gas hole so that the dry nitrogen gas counterflows against the flow of material supplied from the upper part to the lower part of the hopper, the oxygen in the material is replaced by the nitrogen, the hydrolysis and thermal deterioration of the PET are prevented in the course of molding and better molded products can be obtained. In this case, the water in the material can be considerably removed when a heated dry nitrogen gas is used and therefore further favorable results are obtained and thus the staying or residence time of resin in the cylinder can be relatively long when the nitrogen gas counterflow method is employed. 
     As described above, the molten and kneaded material is molded in the specified shape by injection or extrusion molding. In this case, the temperature of the molds is maintained at a fixed level (5° C. higher and lower than the set temperature) and the products with the specified characteristics are stably molded with a slight variation of the quality. For extrusion molding, the temperature of the nozzle should be the melting temperature of resin minus 10° C. and plus 15° C. The mold temperature differs with the characteristics required for the molded products; in case of injection molding, the mold temperature for molding the PET to be non-crystalline should be 10° to 75° C. preferably approximately 30° C., to suddenly cool the PET and to mold the PET in the form of cyrstal and for manufacturing the molded products with excellent heat resistance, the mold temperature should be 120° to 160° C. to promote crystallization of the PET. Moreover, the mold temperature for obtaining the molded products with high strength and heat resistance should be set in the range of 130° to 150° C. The mold for injection molding should be designed to be suitable for molding the PET; for example, the diameter of the gate for molding the PET above or the PET blended with the other polymer can be approximately 1 mm and that for molding the PET blended with the inorganic substance of large grain size and shape such as, for example, glass fiber, should be more than 2 to 3 mm. For molding the molded products with different thicknesses, the mold should be designed so that the cooling water quickly flows through a part of the mold corresponding to a thick wall part of the molded product and the cooling water is circulated for cooling at a high pressure of 5 to 7 kg/cm 2 , and the mold temperature becomes uniform quickly over the corresponding part and the crystallinity of the molded product of the PET can be more appropriately controlled. The mold should be designed and operated so that the temperature of the mold at both sides (the core and the cavity which are split) is uniform wherever possible. If the mold temperature is not appropriate with an uneven distribution of, for example, a difference of more than ±5° C., excellent molded products cannot be obtained. If there is a temperature difference of more than 10° C., the molded products display remarkable variation of the physical properties of the products. Thus, the mold should be carefully designed so that a larger volume of cooling water flows quickly to uniformly cool the mold and the cold water or the like can be used as the cooling medium instead of the room temperature water. Furthermore, the mold should be designed to have the mold volume (total volume of molded product and runner) of more than 25 volume %, preferably 50 volume %, more preferably 90 to 95 volume % of the maximum injection capacity of the injection molding machine. 
     The molding is possible with a mold of which the size is less than 50 volume % and more than 25 volume % of the maximum shot volume of the injection molding machine. In this case, other molding conditions should be strictly controlled to obtain tough molded products. 
     In detail, tough molded products are obtained by molding the material with more than one of various considerations such as, for example, thorough drying of the material to reduce water content from the PET to at greatest less than 0.05 weight %, preferably less than 0.02 weight %, molding under a reduced pressure (less than 100 mm Hg) in the cylinder, counterflowing of dry nitrogen gas to dry the material supplied from the hopper, slightly lowering the molding temperature and controlling the staying time of the material to be within 10 minutes, preferably within 5 minutes. If the mold capacity is more than 50 volume %, tough molded products can be relatively easily obtained even though the molding conditions are not strictly controlled. The shot time for molding the resin is less than 3 minutes especially for large size products, preferably less than one minute, further preferably less than 30 seconds. The residence time of resin in the cylinder can be shortened by controlling the shot time and the capacity of mold and accordingly the hydrolysis and thermal deterioration of the PET can be prevented and tough molded products can be obtained. In this case, if said nitrogen gas counterflow method is employed and the molding is performed under the conditions such as the shot time within one minute, preferably 30 seconds and the mold capacity of more than 25 volume %, preferably 50 volume %, more preferably 90 to 95 volume %, extremely favorable molded products can be obtained. 
     The control of the crystallinity of the molded products is performed by adjusting the preliminary drying condition for the PET and the cooling condition for the mold as described above, and blending of powders of other polymers and inorganic fillers further facilitates the control of crystallinity. Particularly when a metallic powder is blended in the PET, the material is quickly and uniformly cooled as a whole due to excellent heat conductivity of metal and the crystallinity can be controlled satisfactorily. It is effective for control of the crystallinity to appropriately control the shot pressure, for example, to increase the shot pressure so that crystallization is easy. 
     For obtaining the specified molded products using pulverized particles of wastes including of scraps of PET products as a material, a molding machine can be used in which the outlet port of the hopper is given a large inside diameter and the core diameter of the screw shaft, which feeds out and kneads the material supplied from the hopper, opposing to the outlet port of the hopper is considerably small along a distance slightly longer than the inside diameter of the outlet port of the hopper. When this molding machine is used, the pulverized particles of waste PET need not always be blended with pellets of the PET and other polymer or powdery inorganic substances. When the pulverized particles of waste PET are used independently, they can be satisfactorily fed in the screw of the molding machine and easily fed out, thus ensuring efficient and steady molding. FIGS. 1 and 2 show this configuration of the molding machine; FIG. 1 shows an example of a conventional molding machine and FIG. 2 an example of the molding machine useful for the present invention. The body 1a of the horizontal type injection or extrusion molding machine shown in FIG. 1 is made as a cylindrical type and the cylinder chamber 2a is formed in the cylinder 1a. One end of this cylinder chamber 2a in the axial direction is closed. One end of the body 1a in the axial direction is opened at its upper side and the lower end part of funnel type hopper 3a is connected to this opening to communicate the cylinder chamber 2a and the hopper 3a. The columnar screw 4a is provided in the cylinder chamber 2a along the axial direction, and one end part of this screw being held in the bearing 5a and passing through one end face of the cylinder chamber 2a is connected through the joint, reduction gear etc. (not shown) to the motor (not shown). The peripheral surface of the screw shaft of the screw 4a comprises the core 6a and the thread 7a provided on the periphery of the screw 4a. As shown in FIG. 1, in case of the conventional molding machine, the core diameter of the extent of the screw 4a is almost equal over the screw 4a. Contrary to this, in case of the present invention, the inside diameter of the outlet port 8b of the lower part of hopper 3b is made larger than the inside diameter of outlet port 8a of the hopper 3a of the conventional molding machine to facilitate feeding of the material into the cylinder chamber 2b. At the same time, the core diameter of core 6b&#39; of the screw shaft of screw 4b opposite to the outlet port 8b of the hopper 3b is made considerably smaller than the core diameter of the other core 6b of screw 4b (for example, 3 to 20 mm smaller than the other core) along a distance slightly longer than the inside diameter of the outlet port 8b, that is, along approximately 10 cm in case of an ordinary size molding machine to ensure feeding of the material supplied from the hopper 3b to the screw 4b. Since the screw 4b catches satisfactorily even a lightweight material, the material can steadily be fed through the cylinder chamber 2b. Accordingly, when such a molding machine as described above is used, it is not always necessary to improve feeding of the material to the screw by mixing pulverized particles of the PET in the PET pellets to increase the specific gravity of the entire material. The core of the screw just below the outlet port is deep and therefore engagement of the material with the screw can be improved even when the pulverized particles of the PET are used independently. 
     Moreover, as shown in FIGS. 3 and 4, in the conventional molding machine, a material feeding device such as agitator 9 and screw type feeder 10 is provided in the hopper 3c or 3d to prevent difficult feeding of material into the cylinder chamber due to bridging of the material in the hopper, thus ensuring positive feeding of the material into the cylinder chamber and satisfactory feeding of the material to the screw. FIGS. 3 and 4 can be referred to this point. Agitator 9 comprises shaft 11, pulley 12 attached to the upper end of shaft 11 and a plurality of vanes 13 which are orthogonally attached to shaft 11. Vanes 13 are attached to the shaft with equal distance and deviated by every 180 degrees in the sequence from the upper vane to the lower vane and the vanes 13 is made as a short length so that the vanes 13 do not contact the internal surface of hopper 3c. Two vanes are attached to the lower end of shaft 11 and each vane 13 is made spiral and the material supplied into the hopper 3c moves down while being turned as vane 13 rotates and the material is prevented from forming the bridge. The vanes 13 can be simply a flat type. Agitator 9 is connected from pulley 12 to the motor through the transmission belt, reduction gear etc. (these are not shown). The upper end of shaft 11 can be directly connected to the motor. 
     The screw type feeder 10 is provided with thread 15 on the periphery of the screw shaft 14 so that the diameter is gradually smaller from the upper part to the lower part end. When the screw shaft 14 rotates or moves vertically, the material in the hopper goes down while swirling in the hopper 3d. This screw shaft 14 is connected to the motor through the joint, reduction gears etc. (these are not shown) and is rotated or moved vertically by the motor. Accordingly, the material can be fed into the cylinder chamber positively and continuously by using the material feeding devices such as the agitator and screw type feeder as described above and the feeding of material to the screw can therefore be satisfactory. Even though the pulverized particles of waste PET, particularly the film wastes which are difficult to be directly fed are used independently, the molding can be performed positively and the pellets of the PET need not be blended with the pulverized particles of waste PET. 
     EXAMPLE 1 
     Table 1 shows the results of comparison of the strength of molded products which are obtained by using a virgin PET of average molecular weight of 16,000 to 17,000 and water content of less than 0.1 wt. % as a material for molding in both cases. 
     In one case, the temperature of resin is accurately controlled while measuring the temperature of PET material with the surface temperature gauge set in the resin passage of the injection nozzle of the injection molding machine and in the other case the temperature of resin is not controlled. 
     
                       TABLE 1                                                     
______________________________________                                    
          When the temp. of                                               
          resin is accurately                                             
                       When the temp. of                                  
          controlled   resin is not                                       
          (1)    (2)       controlled                                     
______________________________________                                    
Cylinder I      235      235     235                                      
temperature                                                               
         II     250      250     250                                      
(°C.)                                                              
         III    270      270     265-270                                  
Nozzle temperature                                                        
            265      270       270                                        
(°C.)                                                              
Temp. of resin fed                                                        
            265 ± 2                                                    
                     265 ± 2                                           
                               270 ± 5                                 
out from nozzle                                                           
Mold temp. (°C.)                                                   
             50 ± 2                                                    
                      50 ± 2                                           
                                50 ± 2                                 
Strength of molded                                                        
            680      650       555-670                                    
product (kg/cm.sup.2)                                                     
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     The results of similar molding to the above using the PET scraps alone are as shown in Table 2. 
     
                       TABLE 2                                                     
______________________________________                                    
          When the temp. of                                               
                       When the temp. of                                  
          resin is accurately                                             
                       resin is not                                       
          controlled   controlled                                         
______________________________________                                    
Cylinder I      235            235                                        
temperature                                                               
         II     250            250                                        
(°C.)                                                              
         III    270            265-270                                    
Nozzle temperature                                                        
            265            265                                            
(°C.)                                                              
Temp. of resin fed                                                        
            265 ± 2     270 ± 5                                     
out from nozzle                                                           
(°C.)                                                              
Mold temp. (°C.)                                                   
             50 ± 2      50 ± 2                                     
Strength of molded                                                        
            630            400-610                                        
product (kg/cm.sup.2)                                                     
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     As shown above, the variation of the resin temperature is reduced by controlling the resin temperature and, when the PET scraps are used as a material for molding, the molded products of PET of a given quality with less variation of the strength and with high strength are obtained. 
     In this case, the staying time of resin in the cylinder chamber was 10 minutes, the mold capacity was 50% and the shot time was one minute. 
     EXAMPLE 3 
     The strength of molded products obtained from injection molding with the PET of average molecular weight of 16,000 to 17,000 and water content of less than 0.05% blended with other polymer or inorganic fillers while accurately controlling the resin temperature as in case of Example 1 is given in Table 3. In the following all examples, the cylinder temperature was 235° C. for I, 250° C. for II and 270° C. for III, the injection nozzle temperature was 265° to 270° C., the actual temperature of resin fed out from the injection nozzle was 265° C.±2° C. and the mold temperature was 50° C.±2° C. 
     
                       TABLE 3                                                     
______________________________________                                    
                       Tensile strength                                   
                       of molded product                                  
Material and blending ratio                                               
                       (kg/cm.sup.2)                                      
______________________________________                                    
PET virgin material without addition                                      
                       620                                                
PET virgin material with titamium added                                   
                       653                                                
PET film scraps without addition                                          
                       567                                                
PET virgin material + 20% of glass fiber                                  
                       1031                                               
PET scraps + 20% of glass fiber                                           
                       1211                                               
PET scraps + 10% of glass fiber                                           
                       1019                                               
PET scraps + nylon 50% 580                                                
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     In the above table, the blending ratio indicates the weight % for the molded products. (This is the same in the following example.) 
     EXAMPLE 3 
     In the injection molding by accurately controlling the temperature of the PET of average molecular weight of 13,000 to 17,000 and water content of less than 0.05% and varying the mold temperature, the tensile strength and the drawing rate of obtained molded products are as given in Table 4. In this case, the cylinder temperature of the injection molding machine was 250° C., 260° C. and 265° C. The injection nozzle temperature was 265° C., the temperature of resin fed out from the injection nozzle was 265°±2° C. 
     
                       TABLE 4                                                     
______________________________________                                    
                        Tensile                                           
            Mold temp.  strength Drawing                                  
Material (PET)                                                            
            (°C.)                                                  
                        (kg/cm.sup.2)                                     
                                 rate (%)                                 
______________________________________                                    
Virgin material                                                           
            30-35       551                                               
 &#34;          30-35       541                                               
Scrap       20-24       568                                               
 &#34;          30-35         527.8  113.4                                    
 &#34;          45            506.4  32                                       
 &#34;          50          460      4                                        
 &#34;          60          479      4                                        
______________________________________                                    
 
    
     As described above, the molded products with various characteristics were obtained by controlling the temperature of resin to a fixed value and varying the temperature of the molds. When the temperature of the mold was low, tough molded products were obtained since there were many non-crystallized parts in the molded product and crystalline sizes were small even in the crystallized parts. 
     EXAMPLE 4 
     Such products as bushes, knobs, lids, nuts, meter hoods, rollers, gears etc. were molded under the molding conditions shown in Table 6 using the materials blended as shown in Table 5 after drying at 130° C. for 5 to 6 hours to reduce the water content to less than 0.1% before the molding. The characteristics shown in Table 7 were obtained from examinations of the test pieces molded under these molding conditions. In this case, the molecular weight of the PET was 12,000 to 18,000, the staying time of resin in the cylinder chamber was 10 to 15 minutes, the mold capacity was 30 to 60% and the shot time was 1/2 to 3/2 minutes. The variation of the temperature of resin fed out from the nozzle was maintained to be within the set temperature ±3° C. 
     
                       TABLE 5                                                     
______________________________________                                    
No.  Material                                                             
______________________________________                                    
1    PET virgin + polyethylene                                            
                              10%                                         
2    PET virgin + polyethylene                                            
                              20%                                         
3    PET virgin + ABS resin   10%                                         
4    PET virgin + ABS resin   20%                                         
5    PET virgin + nylon 6     25%                                         
6    PET virgin + nylon 6     50%                                         
7    PET virgin + polybutylene terephthalate                              
                              10%                                         
8    PET virgin + polybutylene terephthalate                              
                              20%                                         
9    PET virgin + glass fiber 10%                                         
10   PET (scrap) + glass fiber                                            
                              20%                                         
11   PET (scrap) + glass fiber                                            
                              30%                                         
12   PET (scrap) + glass fiber                                            
                              30%                                         
13   PET (virgin) 1:PET (scrap) 1                                         
14   PET (virgin) 1:PET (scrap) 2 + glass fiber                           
                              20%                                         
15   PET (virgin) 1:PET (scrap) 2 + glass fiber                           
                              30%                                         
16   PET (virgin) 1:PET (scrap) 2 + glass fiber                           
                              30% +                                       
                              quartz 10%                                  
17   PET (virgin) 1:PET (scrap) 1 + glass fiber                           
                              30% +                                       
                              quartz                                      
                              10% +                                       
                              BN 0.5%                                     
18   PET (virgin) 1:PET (scrap) 1 + glass fiber                           
                              30% +                                       
                              carbon 0.5%                                 
______________________________________                                    
 
    
     
                       TABLE 6                                                     
______________________________________                                    
Cylinder temp. °C.                                                 
      Low      High                    Screw                              
      temp.    temp.    Nozzle Mold temp.                                 
                                       revolution                         
No.   part     part     temp. °C.                                  
                               °C.                                 
                                       r.p.m.                             
______________________________________                                    
 1    240      260      270    30-40   68                                 
 2    &#34;        270      &#34;      &#34;       &#34;                                  
 3    &#34;        260      &#34;      &#34;       &#34;                                  
 4    &#34;        &#34;        &#34;      &#34;       &#34;                                  
 5    &#34;        &#34;        &#34;      &#34;       &#34;                                  
 6    &#34;        255      &#34;      &#34;       &#34;                                  
 7    230      260      265    &#34;       &#34;                                  
 8    &#34;        255      &#34;      &#34;       &#34;                                  
 9    260      275      280    &#34;       &#34;                                  
10    &#34;        280      &#34;      &#34;       &#34;                                  
11    &#34;        285      285    &#34;       &#34;                                  
12    270      290      &#34;      140     &#34;                                  
13    250-260  270-275  275    30-40   &#34;                                  
14    260      280      280    140-150 &#34;                                  
15    270      285      285    &#34;       &#34;                                  
16    275      290      &#34;      &#34;       &#34;                                  
17    &#34;        &#34;        &#34;      145-150 &#34;                                  
18    &#34;        &#34;        &#34;      &#34;       &#34;                                  
______________________________________                                    
 Note: The mold temperature was maintained within the set temperature ±
 5° C.                                                             
 
    
     
                       TABLE 7                                                     
______________________________________                                    
                               Heat resistance °C.                 
No.   Strength kg/cm.sup.2                                                
                    Resilience (Softening point)                          
______________________________________                                    
 1    420           Good                                                  
 2    365           &#34;                                                     
 3    540           &#34;                                                     
 4    465           &#34;                                                     
 5    535           Fairly good                                           
                               110                                        
 6    565           Good       120                                        
 7    515           &#34;          60-65                                      
 8    497           &#34;           60                                        
 9    750           Bad        150                                        
10    870           &#34;          180-200                                    
11    1215          &#34;          230-240                                    
12    1105          &#34;          240-250                                    
13    520-600       Good       70-80                                      
14    920           Bad        180-200                                    
15    1260          &#34;          230-240                                    
16    1180          &#34;          240-250                                    
17    1160          &#34;          245-250                                    
18    1280          &#34;          240-245                                    
______________________________________                                    
 
    
     EXAMPLE 5 
     Rod type chips of 2 mm φ were obtained by molding a virgin material of the PET of average molecular weight of 16,000 to 18,000 without preliminary drying treatment (water content was less than 1%) using the vent type extrusion molding machine with vacuum pump under the following conditions. A pressure was provided of less than 50 mm Hg, the temperature of 270° C. at the low temperature part of the cylinder, the temperature of 280° to 290° C. at the high temperature of the cylinder and the nozzle temperature of 275° to 280° C. of which variation was maintained to be within ±3° C., the size of screw of 90 mm and the cooling water of less than 50° C. When the rod type chip products were bent many times, they were not broken and the molecular weight was barely reduced, approximately less than 5%, and the molded products with the same characteristics as when the PET was previously dried at 130° C. for 4.5 to 6 hours were obtained. This was the same when PET scraps were used as the PET material. 
     EXAMPLE 6 
     The products such as nuts, rollers etc. were molded as in Example 4 by molding the virgin material of PET and PET scraps which were blended with 10 to 40 weight % of inorganic fillers such as glass fiber, feldspar, quartz without the preliminary drying treatment using the vent type injection molding machine under the condition that the material contained approximately 0.5% of water content and the pressure in the cylinder chamber was less than 100 mm Hg. The physical properties of these molded products were satisfactory and the crystallized products were hardly broken and were extremely strong even when hammered or powerfully thrown onto a wall. Reduction of the pressure in the cylinder to less than 100 mm Hg did not affect the physical properties of the molded products even though the material contained approximately 0.5% of water. 
     EXAMPLE 7 
     Cylindrical dome type products of approximately 2 mm in thickness. 13 cm in height and 8 cm in inside diameter were molded with the PET blended with other polymers and inorganic fillers as in case of Example 4 after introducing dry nitrogen gas from the lower part of the hopper to make it counterflow against the flow of material and to replace with air in the material when feeding the material through the hopper, under the conditions such as the temperature at the low temperature part of the cylinder of 250° to 255° C. The temperature at the high temperature part of the cylinder of 275° to 280° C. and nozzle temperature of 280° C. of which variations were respectively maintained to be ±3° C., the mold temperature of 30° to 35° C., screw revolution of 70 r.p.m. and the cycle of one shot of 40 seconds. The section of this molded product presents a blue color which indicates evidently that the PET has not been oxidized and deteriorated by oxygen during the molding as compared with the surface of the products which are molded without counterflow of nitrogen gas and have a yellow section. The toughness of this molded product is extremely high. For example, when a vertically moving hammer strikes the dome type molded product the product molded without using nitrogen gas is broken by hammering 3 to 5 times while the product molded with nitrogen gas is broken by hammering 6 to 10 times and the impact resistance of the latter molded product is improved by 30 to 50%. This effect brings about the similar results regardless of the crystallinity of molded products. For example, this is the same with a molded product of 3 ounces obtained from a machine of 11 ounces. 
     EXAMPLE 8 
     In molding a roller of approximately 12 mm in wall thickness and approximately 3 cm in diameter with a circular hole of 1.5 mm diameter, using a virgin material and scraps of the PET of average molecular weight of 12,000 to 17,300 and water content of less than 0.05 weight %. The effect on the staying time of the PET in the cylinder was examined using a mold (with one cavity) for a product of approximately 12 g. 
     1. Molding conditions 
     Drying condition for material: 130° C., 5-6 hr 
     Cylinder temperature at low temperature part: 250°-260° C. 
     Cylinder temperature at high temperature part: 270°-275° C. 
     Screw revolution: approx. 70 r.p.m. 
     Mold temperature: 30° C.±2° C. 
     1 shot time: 90 seconds 
     Size of the injection molding machine: 1, 3.5 and 5 ozs 
     2. Relations between the staying time and the physical properties of molded products 
     
                       TABLE 8                                                     
______________________________________                                    
Size of  Mold vol-  Staying Breaking                                      
                                    Dropping                              
molding  ume/Max.   time    strength                                      
                                    height to                             
machine  shot volume                                                      
                    (min)   kg/cm.sup.2                                   
                                    breakage                              
______________________________________                                    
(1) 5 ozs     1/10      45-60 10 or less                                  
                                       1 m or less                        
(2) 3.5 ozs  1/5        24-30 300-600 40 m or more                        
(3) 1 oz     1/2        12-15 1000-1300                                   
                                      50 m or more                        
______________________________________                                    
 Note: The mold capacity is the total of the volumes of the molded product
 and the runner.                                                          
 
    
     The above breaking strength (pressure test) was obtained when the roller shown above in a longitudinal position with width of 12 mm and height of 3 cm was depressed and the product shown in (2) and (3) in a cross position showed the strength more than 5000 kg/cm 2 . In case of condition (3), no breakage was observed even when the product was powerfully thrown against the wall. 
     Accordingly, the residence time of the PET in the heated cylinder should be within 15 minutes to obtain tough molded products and the size of mold should be more than 50% of the maximum shot volume of the molding machine. 
     EXAMPLE 9 
     Such products as bushes, knobs, lids, nuts, meter hoods, rotors, gears, bobbins were molded with the pulverized particles of film scraps of PET of average molecular weight of 12000 to 13500 and water content of less than 0.05% blended with the materials shown in Table 9 under the conditions shown in Table 9. The characteristics of these molded products are shown in Table 10. In this case, the residence time was 5 to 15 minutes, the mold capacity was 20 to 60% and the shot time was 30 seconds to 2 minutes. 
     
                       TABLE 9                                                     
______________________________________                                    
Molding conditions                                                        
           Cylinder temp.                                                 
                 Low     High        Screw                                
                 temp.   temp. Nozzle                                     
                                     revolu-                              
                                           Mold                           
     Blended     part    part  temp. tion  temp.                          
No.  material    °C.                                               
                         °C.                                       
                               °C.                                 
                                     r.p.m.                               
                                           °C.                     
______________________________________                                    
1    Polyethylene,                                                        
                 240     270   270   68    30-40                          
     10 weight %                                                          
2    Polyethylene,                                                        
                 240     260   &#34;     &#34;     &#34;                              
     20 weight %                                                          
3    ABS resin,  240     260   270   68    30-40                          
     5 weight %                                                           
4    ABS resin,  240     260   &#34;     &#34;     &#34;                              
     10 weight %                                                          
5    Nylon 6,    240     260   &#34;     &#34;     &#34;                              
     25 weight %                                                          
6    Nylon 6,    230     255   &#34;     &#34;     &#34;                              
     50 weight %                                                          
7    Polybutylene                                                         
                 230     260   &#34;     &#34;     &#34;                              
     terephthalate,                                                       
     10 weight %                                                          
8    Polybutylene                                                         
                 230     255   &#34;     &#34;     &#34;                              
     terephthalate,                                                       
     20 weight %                                                          
9    Glass fiber,                                                         
                 250     275   280   &#34;     &#34;                              
     10 weight %                                                          
10   Glass fiber,                                                         
                 250     275   280   68    30-40                          
     20 weight %                                                          
11   Glass fiber,                                                         
                 250     280   &#34;     &#34;     &#34;                              
     30 weight %                                                          
12   Glass fiber,                                                         
                 250     280   &#34;     &#34;     &#34;                              
     30 weight % +                                                        
     feldspar,                                                            
     10 weight %                                                          
______________________________________                                    
 
    
     
                       TABLE 10                                                    
______________________________________                                    
Physical Properties of Molded Products                                    
                               Heat resistance                            
No.   Resilience Strength (kg/cm.sup.2)                                   
                               (softening temp.)                          
______________________________________                                    
1     Good       400                                                      
2     &#34;          350                                                      
3     &#34;          400                                                      
4     &#34;          300                                                      
5     &#34;          400           110° C.                             
6     &#34;          350           125° C.                             
7     &#34;          470                                                      
8     Bad        450                                                      
9     &#34;          400           150° C.                             
10    &#34;          850           180-200° C.                         
11    &#34;          1250          230-240° C.                         
12    &#34;          1100          245-250° C.                         
______________________________________                                    
 
    
     EXAMPLE 10 
     The similar products to Example 9 were molded with the pulverized particles of PET scraps of average molecular weight of 12000 to 13500 to which PET pellets of average molecular weight of 15000 to 17000 and other substances were added to control the water content to less than 0.05% under the molding conditions shown in Table 11. The characteristics of these molded products are as shown in Table 12. 
     
                       TABLE 11                                                    
______________________________________                                    
Molding conditions                                                        
               Cylinder temp.                                             
     PET                 Low   High                                       
     scrap:              temp. temp. Nozzle                               
                                           Mold                           
     PET     Blended     part  part  temp. temp.                          
No.  pellet  material    °C.                                       
                               °C.                                 
                                     °C.                           
                                           °C.                     
______________________________________                                    
13   1:1       --        250   270   270   30-40                          
14   1:2       --        &#34;     &#34;     &#34;     &#34;                              
15   2:1       --        &#34;     &#34;     &#34;     &#34;                              
16   3:1       --        &#34;     &#34;     &#34;     &#34;                              
17   4:1       --        &#34;     &#34;     &#34;     &#34;                              
18   2:1     Glass fiber 255   275   280   145                            
             10 weight %                                                  
19   2:1     Glass fiber &#34;     &#34;     &#34;     &#34;                              
             20 weight %                                                  
20   2:1     Glass fiber 260   280   &#34;     &#34;                              
             30 weight %                                                  
21   2:1     Glass fiber,                                                 
                         265   285   285   145                            
             30 weight % +                                                
             feldspar,                                                    
             10 weight %                                                  
22   2:1     Glass fiber,                                                 
                         &#34;     &#34;     &#34;     &#34;                              
             30 weight % +                                                
             quartz,                                                      
             10 weight %                                                  
______________________________________                                    
 
    
     
                       TABLE 12                                                    
______________________________________                                    
Physical Properties of Molded Products                                    
                               Heat resistance                            
No.   Resilience Strength (kg/cm.sup.2)                                   
                               (softening temp.)                          
______________________________________                                    
13    Good       450-500       70-75° C.                           
14    &#34;          &#34;             &#34;                                          
15    Good       450-500       70-75° C.                           
16    &#34;          &#34;             &#34;                                          
17    &#34;          &#34;             &#34;                                          
18    Bad        700           150° C.                             
19    &#34;          900           210° C.                             
20    &#34;          1250          240° C.                             
21    &#34;                        245° C.                             
22    &#34;                        245-250° C.                         
______________________________________                                    
 
    
     As shown in Example 9 and Example 10, the pulverized particles of scraps and waste molded products of the PET can be used as is and need not be pelletized in advance. Any types of scraps can be molded after having been pulverized. Accordingly, the manufacturing processes can be simplified, scraps can be reproduced efficiently at low costs and a large quantity of fabric material such as glass fiber can be added and need not be cut in a small size before use, and can be blended as is in length, thus obtaining tough molded products with satisfactory characteristics. Since PET pellets, pellets of other polymers, fibers, powdery inorganic substances etc. can be added to the scraps or pulverized particles of waste PET products, inefficient feeding of the material to the screw of the molding machine due to small specific gravity of the pulverized particles of the PET is eliminated, apparent specific gravity of the entire material becomes large and the material can be satisfactorily fed to the screw and passed through the cylinder positively and efficiently, and thus tough products with various characteristics can be injection- or extrusion-molded. 
     EXAMPLE 11 
     Pellets of the PET were molded with the materials shown below by the vent type extrusion molding machine with vacuum pump under the molding conditions given below. In this case, the average molecular weight of the PET was 12000 to 18000, water content was less than 1%, the pressure in the cylinder was maintained at 50 mm Hg and the staying time of the material in the cylinder was 3 to 4 minutes. 
     
                       TABLE 13                                                    
______________________________________                                    
                     Molding condition                                    
Material             (Temp. in cylinder °C.)                       
     Kind of   Blended material                                           
                             Low temp.                                    
                                     High temp.                           
No.  PET       (weight %)    part    part                                 
______________________________________                                    
 1   Pellet    Polyethylene, 10                                           
                             240     270                                  
 2   &#34;         Polyethylene, 20                                           
                             230     270                                  
 3   &#34;         Nylon 6, 20   250     270                                  
 4   &#34;         Nylon 6, 40   240     260                                  
 5   &#34;         ABS resin, 5  230     265                                  
 6   &#34;         ABS resin, 10 230     265                                  
 7   &#34;         Polybutylene  240     265                                  
               terephthalate, 10                                          
 8   &#34;         Polybutylene  240     260                                  
               terephthalate, 20                                          
     Pellet:                                                              
     pulverized                                                           
     particles                                                            
     of film                                                              
 9   1:1       Glass fiber, 20                                            
                             250     270                                  
10   2:1        &#34;            &#34;       &#34;                                    
11   3:1        &#34;            &#34;       &#34;                                    
12   1:2        &#34;            &#34;       &#34;                                    
13   1:3        &#34;            &#34;       &#34;                                    
14   1:4        &#34;            &#34;       &#34;                                    
15   1:1       Glass fiber, 10                                            
                             250     280                                  
16   1:1       Quartz, 20    &#34;       &#34;                                    
17   1:1       Quartz, 30    &#34;       &#34;                                    
18   1:1       Quartz, 10    &#34;       &#34;                                    
19   1:1       Feldspar, 10  &#34;       &#34;                                    
20   1:1       Glass fiber, 20 +                                          
                             &#34;       &#34;                                    
               feldspar, 10  &#34;       &#34;                                    
21   1:1       Glass fiber, 20 +                                          
                             &#34;       &#34;                                    
               quartz, 10    &#34;       &#34;                                    
______________________________________                                    
 
    
     The pellets shown in Table 13 which were manufactured under the above conditions were injection molded to obtain various types of molded products. The physical properties of these molded products are as shown in Table 14. 
     In this case, the screw revolution was 68 r.p.m. and the mold temperature was 40° to 50° C. for Nos. 1 to 8 and 45° to 50° C. for Nos. 9 to 21. The water content of each pellet was less than 0.05%, the mold capacity was 30 to 60% and the shot time was 0.5 to 2 minutes. 
     
                                           TABLE 14                                
__________________________________________________________________________
                      Physical properties of                              
                      molded products                                     
                                 Heat                                     
Molding temperature   Impact     resistance                               
    Low temp.                                                             
          High temp.                                                      
                Nozzle                                                    
                      resis-     (softening                               
No. part  part  temp. tance                                               
                           Resilience                                     
                                 temp.)                                   
__________________________________________________________________________
 1     240° C.                                                     
             265° C.                                               
                   270° C.                                         
                      3    Good  100° C.                           
 2  230   260   265   6    Excellent                                      
                                 120° C.                           
 3  250   265   270   3    Good  100° C.                           
 4  240   260   265   5    Good  120° C.                           
 5  230   260   265   4    Good   65° C.                           
 6  220   255   265   5    Good   60° C.                           
 7  230   260   265   4    Good   65° C.                           
 8  230   255   265   5    Good   60° C.                           
 9  250   270   275   7    Good  180-200° C.                       
10  &#34;     &#34;     &#34;     8    Good  &#34;                                        
11  &#34;     &#34;     &#34;     8    Good  &#34;                                        
12  &#34;     &#34;     &#34;     6    Good  180-200° C.                       
13  &#34;     &#34;     &#34;     6    Good  &#34;                                        
14  &#34;     &#34;     &#34;     6    Good  &#34;                                        
15  260   275   280   6    Bad   130° C.                           
16  &#34;     &#34;     &#34;     8    Bad   200° C.                           
17  &#34;     &#34;     &#34;     6    Bad   235° C.                           
18  &#34;     &#34;     &#34;     4    Fairly good                                    
                                 135° C.                           
19  &#34;     &#34;     &#34;     3    Fairly good                                    
                                 130° C.                           
20  &#34;     &#34;     &#34;     6    Bad   230° C.                           
21  &#34;     &#34;     &#34;     6    Bad   235° C.                           
__________________________________________________________________________
 
    
     The impact resistance was measured from the number of times of dropping a molded product (bush) which was mounted on one end of a steel tube of 80 cm in length and 3/4&#34; in diameter from a height of 1 m in the vertical direction until the molded product was broken. 
     As described above, when the PET of average molecular weight of more than 10,000 is blended with less than 60 weight % of other polymers and inorganic fillers, this blended material is extruded into specified shapes after the PET and other polymers and inorganic fillers have been melted and kneaded each other and a material for molding which integrally contains the PET and other polymers and inorganic fillers is manufactured, this material for blending does not nearly contain water and oxygen which cause hydrolysis and thermal deterioration and can be directly used without various blendings shortly before the molding. Moreover, the scraps and wastes of the PET can also be used and therefore excellent tough molded products with further improved characteristics of the PET can be manufactured easily, positively and stably at low costs. 
     EXAMPLE 12 
     The test piece was made at various mold temperatures using a mixture shown in Table 15 which was prepared by adding glass fiber and others to virgin PET (A) of average molecular weight of approximately 17,000, virgin PET (B) of average molecular weight of approximately 25,000 and waste PET of average molecular weight of approximately 13,000 (water content of each material was less than 0.1 weight %), and the results of measurement of the impact strength (sharpy impact value) were obtained as shown in Table 15. 
     The cylinder temperature was 250° C. (I), 260° C. (II) and 280° C. (III) and the nozzle temperature was 280° C. The temperature of resin flowing out from the nozzle was accurately controlled and the mold temperature was also accurately controlled. The residence time of resin in the cylinder was within 10 minutes, screw revolution 67 r.p.m., mold capacity approximately 30 volume %, shot time approximately 1 minute. 
     
                                           TABLE 15                                
__________________________________________________________________________
Material blending ratio (weight %)                                        
                                  Impact                                  
Virgin                        Mold                                        
                                  resistance                              
                                        Tensile                           
PET     Waste                                                             
            Glass                                                         
                Glass                                                     
                    Feldspar                                              
                         Quartz                                           
                              temp                                        
                                  kg/cm.sup.2                             
                                        strength                          
No.                                                                       
   A B  PET fiber                                                         
                balls                                                     
                    powder                                                
                         powder                                           
                              °C.                                  
                                  with notch                              
                                        (kg/cm.sup.2)                     
__________________________________________________________________________
1  35   35  30                 25 17.21 1242                              
2  35   35      30            &#34;   3.3   457                               
3  40   40  10  10            &#34;   5.16  816                               
4  40   40   5   5  5    5    &#34;   2.9   660                               
5  35   35  30                 50 11.32 1269                              
6  40   40  10  10            &#34;   5.31  818                               
7  35   35  30                145 5.18  1007                              
8  35   35      30            &#34;   2.1   500                               
9    100                       25 4.1   565                               
10   50 50                    &#34;   3.3   582                               
11   40 40  20                135 6.74  771                               
12   40 40  20                145 5.7   842                               
__________________________________________________________________________
 
    
     As known from the results shown above, the injection molded product with excellent impact resistance can be obtained in molding at a low temperature of the mold. It is recommended that the mold temperature be raised to obtain the injection molded products with excellent heat resistance. 
     As shown in the above results, in case of the molding for which the mold temperature is particularly raised to a high degree, a considerable variation of physical properties (for example, No. 11 and No. 12) is observed with respect to 10° C. difference of the mold temperature and accordingly it is known that the mold temperature should be controlled so that the variation of the mold temperature is within 5° C. higher and lower than the set temperature.