JPH08224736A - Method and apparatus for manufacturing thermoplastic resin molded intermediate - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a thermoplastic resin molding intermediate having a long-term durability, such as a polyester resin, which relates to a method and a manufacturing apparatus for a thermoplastic resin molding intermediate. [Structure] When a thermoplastic resin molding intermediate is produced by heating and melting a thermoplastic resin and then cooling and molding, the temperature of the thermoplastic resin is 70 ° C. before heating and melting the thermoplastic resin. As described above, the thermoplastic resin is dried while maintaining the temperature range lower than the melting point of the thermoplastic resin by 10 ° C. or more. At this time, the dry air can be supplied while maintaining the temperature of the thermoplastic resin at 70 ° C. or higher and 10 ° C. or higher lower than the melting point of the thermoplastic resin.
Dry air heated to a temperature range of 0 ° C. or higher and 10 ° C. or higher lower than the melting point of the thermoplastic resin can be supplied. According to the measurement result of the test piece molded by using the thermoplastic resin molding intermediate thus manufactured, the tensile strength and the bending strength were remarkably improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing a thermoplastic resin molding intermediate such as a polyester resin having long-term durability.

[0002]

2. Description of the Related Art A resin such as a polyester resin is a thermosetting resin which is three-dimensionally cross-linked by heating to be insoluble in any solvent, and a resin which is melted by heating and reversibly returns to its original solid when cooled. The present invention is effective for the latter thermoplastic resin, which is roughly classified into two types.

The thermoplastic polyester resin includes a so-called aromatic type such as polyethylene terephthalate (PET) having a benzene ring in its molecular chain, and a type consisting of all aliphatic hydrocarbons. It also includes biodegradable resins (for example, poly-3-hydroxybutyrate; HB, etc.), which are attracting attention in terms of environmental protection and which are completely decomposed by microorganisms in soil.

Since any resin has an ester bond, many kinds of resins are relatively easy to synthesize, and usually, they are synthesized by polycondensation by forming an ester bond of dicarboxylic acid and glycol, and therefore, these substances are used. It has the advantage that various resins can be synthesized under similar synthetic conditions by the selection and combination of.

[0005]

However, the point of having the ester bond is also a drawback of the resin. That is, when this type of resin is used or stored for a long period of time or under chemically severe conditions, a part of the ester bond is hydrolyzed to break the polymer chain, which causes deterioration of the physical properties of the material. There was a problem. It is known from another study that when the main chain is cleaved, it is important to suppress this reaction because even if the cleaved part is very small, it has a great influence on the deterioration of material properties such as strength. Is.

It is an object of the present invention to provide a method and an apparatus for producing a thermoplastic resin molding intermediate such as a polyester resin having long-term durability.

[0007]

In the method for producing a thermoplastic resin molding intermediate according to the present invention, in order to reduce the above problems, the thermoplastic resin is heated and melted, and then cooled and molded. When a thermoplastic resin molding intermediate is produced, the temperature of the thermoplastic resin is maintained at 70 ° C. or higher and 10 ° C. or lower than the melting point of the thermoplastic resin before the thermoplastic resin is melted by heating. The process of doing is adopted.

In this case, the thermoplastic resin can be maintained at a temperature range of 70 ° C. or higher in a temperature range lower than the melting point of the thermoplastic resin by 10 ° C. or more, and dry air can be supplied to the thermoplastic resin. Further, in this case, dry air heated to 70 ° C. and a temperature range lower than the melting point of the thermoplastic resin by 10 ° C. or more can be supplied to the thermoplastic resin.

Further, in the apparatus for producing a thermoplastic resin molding intermediate according to the present invention, the thermoplastic resin has means for heating and melting the thermoplastic resin, and means for cooling and molding the melted thermoplastic resin. A device for producing a resin molding intermediate is provided with means for maintaining the temperature of the thermoplastic resin at 70 ° C. or higher and 10 ° C. or more lower than the melting point of the thermoplastic resin before heating and melting the thermoplastic resin. Adopted the configuration.

In this case, there is provided a means for maintaining the temperature of the thermoplastic resin at 70 ° C. or higher within a temperature range lower than the melting point of the thermoplastic resin by 10 ° C. or more, and a means for supplying dry air to the thermoplastic resin. Can be Further, in this case, the thermoplastic resin may be provided with a means for supplying dry air in a temperature range of 70 ° C. or higher and 10 ° C. or higher lower than the melting point of the thermoplastic resin.

[0011]

In order to alleviate the above problems, the mechanism of hydrolysis was examined, and the following was found. 1. The resin may contain a trace amount of acidic or basic (alkaline) substance and water depending on impurities contained in the raw material during the synthesis of the resin, the pH (hydrogen ion concentration) environment at the time of synthesis, or the like. 2. Generally, hydrolysis is greatly accelerated by the presence of residual water in the resin along with the presence of acid or base (alkali). 3. For this reason, it is particularly desirable to store the resin raw material in a dry environment as much as possible, but due to the actual storage environment and the storage being relatively long-term, the resin absorbs ambient moisture and becomes more than immediately after manufacturing. Often contains water. 4. Further, the hydrolysis of the resin has a particularly high rate in the state where the resin is melted at a high temperature, so that it is particularly desirable that the water content is small at this stage.

In the present invention, in order to suppress the hydrolysis reaction of the thermoplastic resin due to the water content, the thermoplastic resin is heated before the kneading by heating the thermoplastic resin, preferably immediately before the kneading, to remove the water content. Alternatively, dry air is supplied to the thermoplastic resin.

Generally, a thermoplastic resin is a powder when it is synthesized from raw materials, and after being transported and stored in this state, it is mixed with other raw materials (a filler or additives such as plasticizers and pigments), A resin product is molded in a pellet state, which is a thermoplastic resin molding intermediate. Usually, the raw materials are mixed by kneading by heating the resin to melt it once and then mixing it with a kneading extruder. In order to suppress the deterioration of the resin, it is desirable that the kneading is performed only once, but it may be performed twice or more depending on the process.

In the present invention, when the raw material resin powder is introduced into this kneading extruder, the temperature inside the hopper is heated to 70 ° C. or higher at which the water contained in the raw material resin powder can be sufficiently dried. The feature is that dry air is supplied into the hopper together with it, if necessary. If this temperature is lower than 70 ° C, the heating effect is not sufficiently exhibited.

At this time, the higher the temperature of the raw material resin powder is, the greater the drying effect is. However, when the raw material resin powder is heated near the melting point of the resin itself, the raw material resin powders are partially fused to each other to form a lump, a so-called blocking phenomenon Cause This is because the melting point of the resin has a range, and a part of the resin begins to melt near the melting point, and it is considered that the temperature is 10 ° C. or more lower than the melting point of the thermoplastic resin.

According to the present invention, since a small amount of water contained in the raw material resin powder can be evaporated to reduce its content, it is possible to reduce the water content when the raw material resin powder is melted at a high temperature. As a result, it is possible to greatly suppress the deterioration of the physical properties of the resin due to hydrolysis during melting.

It should be noted that the present invention is applicable to all resins other than those used in the following examples, particularly resins that easily absorb water,
Alternatively, it is clear from the principle that the present invention can be applied to a resin of a type that easily deteriorates in physical properties due to hydrolysis, such as a polyester-based thermoplastic resin. Also, the present invention
In addition to the above-mentioned method for producing a thermoplastic resin molding intermediate, it also includes an apparatus for producing a thermoplastic resin molding intermediate for carrying out the production method.

[0018]

Embodiments of the present invention will be specifically described below with reference to the drawings. (First Embodiment) FIG. 1 is a schematic structural explanatory view of an apparatus for manufacturing a thermoplastic resin molding intermediate according to the first embodiment. In this figure, 1 is a kneading extrusion device, 2 is a kneading cylinder, 3 is a kneading extrusion screw, 4 is a kneading extrusion motor, 5 is a nozzle, 6 is a heater, 7 is a material feeding device, 8 is a hopper, 9 is an air hole, 10 is a material supply screw, 11 is a material supply motor, 12 is a lid, 13 is an air hole, 14 is a heat retaining heating element, 1
5 is a dry air blower, 16 is a dry air duct, 17 is a cooling device, 18 is a cooling water tank, 19 is a guide roller, 20
Is cooling water, 21 is a pelletizer, 22 is a pelletizer box, 23 is a rotary cutter, 24 is a pressing roller, 25
Is a thermoplastic resin molding intermediate storage bag, 26 is a thermoplastic resin powder, and 27 is a thermoplastic resin molding intermediate.

The apparatus for producing a thermoplastic resin molding intermediate of this embodiment comprises a kneading / extruding apparatus 1, a material supplying apparatus 7, a cooling apparatus 17 and a pelletizer 21. And
The kneading / extruding device 1 extends substantially horizontally and has a kneading cylinder 2 having a nozzle 5 at its downstream end, a kneading / extruding screw 3 extending from the center of the kneading cylinder 2 and a kneading / extruding motor 4 for rotationally driving the kneading / extruding screw 3. And a heater 6 on the outer periphery thereof.

The material supply device 7 connected upstream of the kneading / extruding device 1 has a hopper 8 having an air hole 9 in the vicinity of its lower end, a material supply screw 10 extending vertically into the hopper 8, and this material supply screw. Material supply motor 11 for rotating 10 and lid 1 having air holes 13
2, a heat retaining heating element 14 is provided around the hopper 8, and a dry air blower 15 is connected to an air hole 9 near the lower end of the hopper 8 through a dry air duct 16.

The cooling device 17 includes a cooling water tank 18 containing cooling water 20 and a nozzle 5 at the downstream end of the kneading / extruding device 1.
It is provided with a guide roller 19 for guiding the uncured thermoplastic resin extruded from.

The pelletizer 21 comprises a pelletizer box 22 and a rotary cutter 23 which is driven to rotate therein.
And a pressing roller 24. In addition, a thermoplastic resin molded intermediate storage bag 25 for storing the thermoplastic resin molded intermediate pelletized by the pelletizer 21 is attached to the pelletizer box 22.

When a thermoplastic resin molding intermediate is manufactured by this thermoplastic resin molding intermediate manufacturing apparatus, the thermoplastic resin powder 26 is added to the hopper 8 of the material supplying device 7 connected upstream of the kneading / extruding device 1. , Other resins and pigments are supplied as needed, and the thermoplastic resin is covered with a lid 12 having an air hole 13 and a dry air blower 15 through an air hole 9 near the lower end of the hopper 8 through a dry air duct 16. Dry air is sent at a wind speed of about 3 liters / minute so that the resin powder 26 cannot be blown up, and the temperature is raised to about 80 to 100 ° C. by the heat retaining heating element 14 provided in the periphery of the hopper 8. The material supply screw 1 which is dried and rotationally drives the thus dried thermoplastic resin powder 26 by the material supply motor 11.
0 to supply it to the upstream of the kneading and extruding device 1.

The thermoplastic resin powder 26 supplied upstream of the kneading / extruding apparatus 1 is melted by the heater 6 provided on the outer circumference of the kneading cylinder 2, and is kneaded by the kneading / extruding screw 3 which is rotationally driven by the kneading / extruding motor 4. Then, the thermoplastic resin having the sectional shape of the nozzle 5 is extruded from the nozzle 5 at the downstream end.

The thermoplastic resin extruded from the nozzle 5 is passed through the cooling water 20 in the cooling water tank 18 of the cooling device 17 by the guide roller 19 to be cooled and solidified.

The thermoplastic resin solidified by the cooling device 17 is guided to the pelletizer box 22 of the pelletizer 21, cut into a certain length by the rotary cutter 23 and the pressing roller 24 that are driven to rotate, and pelletized. The thermoplastic resin molding intermediate 27 is housed in the thermoplastic resin molding intermediate storage bag 25.

When poly-3-hydroxybutyrate (HB) is copolymerized with poly-3-hydroxyvalate (HV) by using this apparatus for producing a thermoplastic resin molding intermediate, the heat generated from the resin having good mechanical properties is obtained. A plastic resin molding intermediate can be manufactured. That is, a copolymer of HB and HV (HV ratio of about 5%, number average molecular weight of about 6 × 10 ⁴ , melting point of 150 ° C.) was kneaded and melted to produce 15 kg of pellets, which is a thermoplastic resin molding intermediate.

Thereafter, the pellets were dried at 80 ° C. for 20 hours, stored in an environment of a temperature of 20 ± 3 ° C. and a humidity of 30 to 80% for 1 month, and then dried at 80 ° C. for 8 hours, and then 2
A test piece was formed by injection molding within 4 hours. Diameter of 0.1 to 1 at a position near the gate on 10% of the formed test pieces
About 1% of defective products generated a large number of bubbles of about mm. Among the formed test pieces, those having no bubbles having a diameter of 0.3 mm or more were left for 20 hours in an environment of room temperature of 20 ° C. and humidity of 40 to 70%, and then the mechanical strength was measured.

The molded test piece was heated at a temperature of 20.
90 ℃ after storing for 7 hours in an atmosphere of ℃ and humidity of 50%
The weight change before and after drying for 30 hours was measured and analyzed by a drying method in which the amount of decrease in weight was taken as water, and it was found that the water content was 0.5 to 0.9% by weight.
After the mechanical strength was specified, the test piece was also tested at a temperature of 50
It was left for 60 days in an environment of ℃ and 70% humidity and the change in mechanical strength was traced.

FIG. 2 is an explanatory view of the mechanical strength measurement result of the thermoplastic resin molding intermediate of the first embodiment, (A) shows the tensile strength, and (B) shows the bending strength. The horizontal axis of this figure is time (days), and the vertical axis is tensile strength (kg).
f / mm ² ) and bending strength (kgf / mm ² ). According to this figure, the mechanical strength of the thermoplastic resin molded intermediate according to this example is lower in both tensile strength and bending strength than the test piece of the first comparative example described later, which is not according to this example. I understand.

(First Comparative Example) In order to compare with the method for producing a thermoplastic resin molding intermediate of the first example, substantially the same except for the step of drying the thermoplastic resin powder which is the characteristic of the first example. A thermoplastic resin molding intermediate was manufactured under the conditions.

Copolymer of HB and HV (HV ratio about 5
%, A number average molecular weight of about 6 × 10 ⁴ , and a melting point of 150 ° C.) were used to produce resin pellets by an ordinary process. That is, the resin powder was pelletized by a kneading extruder, dried at 80 ° C. for 20 hours, stored at room temperature in a cool and dark place for several months, dried at 80 ° C. for 8 hours, and then injection-molded into a plate shape within 24 hours. A test piece was formed.

A large amount of gas, which is thought to be residual water, was generated during molding, and a diameter of 0.1% was formed at a position near the gate of 10% of the molded product.
Many bubbles of about 1 mm were generated. Among the molded test pieces, those without bubbles having a diameter of 0.3 mm or more were allowed to stand for 20 hours in an environment of room temperature of 20 ° C. and humidity of 40 to 70%, and then the mechanical strength was measured.

The molded product was stored in an atmosphere of a temperature of 20 ° C. and a humidity of 50% for 7 days, and then the molded product was analyzed by a drying method to find that the resin contained 1.0 to 1.9% by weight. I understood. Next, when the change in mechanical strength was traced by leaving the test piece in an environment of a temperature of 50 ° C. and a humidity of 70% for 60 days, as shown in FIG. 2, both tensile strength and bending strength were measured. , A remarkable decrease was observed.

(Second Embodiment) In this embodiment, the inside of the hopper is heated to 100 by a heat retaining heating element 14 provided around the hopper of the material feeding device connected upstream of the kneading and extruding device shown in FIG. Heat up to 120 ° C., and further supply dry air into the hopper at a rate of 3 liters / minute to dry a commercially available polybutylene terephthalate (PBT) powder, which is a thermoplastic resin powder, and knead and melt at 280 ° C. to pellet 15 kg. Was manufactured.

Thereafter, the pellets were dried at 80 ° C. for 20 hours, stored at a temperature of 20 ± 3 ° C. and a humidity of 30 to 80% for 1 month, and then dried at 80 ° C. for 8 hours and then injected within 24 hours. A test piece was formed by molding. The test piece is the first
After processing in the same manner as in the example and specifying the mechanical strength,
The change in mechanical strength was traced by leaving it in an environment of a temperature of 70 ° C. and a humidity of 80% for 60 days.

FIG. 3 is an explanatory view of the mechanical strength measurement result of the thermoplastic resin molding intermediate of the second embodiment, (A) shows the tensile strength, and (B) shows the bending strength. The horizontal axis of this figure is time (days), and the vertical axis is tensile strength (kg).
f / mm ² ) and bending strength (kgf / mm ² ). According to this figure, the mechanical strength of the thermoplastic resin molded intermediate according to this example is lower in both tensile strength and bending strength than the test piece of the second comparative example described later, which is not according to this example. I understand.

(Second Comparative Example) In the second comparative example, a commercially available powder of polybutylene terephthalate (PBT) was used in the same manner as in the second example, and the thermoplastic resin powder characteristic of Example 2 was dried. Resin pellets were manufactured under the same conditions and steps except for the steps.

That is, the resin powder was pelletized by a kneading extruder, stored at a temperature of 20 ± 3 ° C. and a humidity of 30 to 80% for 1 month, and then dried at 80 ° C. for 8 hours and then injection molded within 24 hours. A test piece was formed.

A large amount of gas, which is thought to be residual water, was generated during molding, and a diameter of 0.1% was formed at a position near the gate of 3% of the molded product.
Bubbles of about 1 mm were generated. Of the molded test pieces, those without bubbles with a diameter of 0.3 mm or more are tested at a temperature of 20 ° C.
After standing for 20 hours in an environment of humidity 40 to 70%, the mechanical strength was measured.

The water content of this molded product was analyzed by a drying method, and it was found that the resin contained 1.0 to 2.5% by weight of water. Next, the test piece is heated to 70
When the change in mechanical strength was traced by leaving it for 60 days in an environment of ° C and humidity of 80%, a remarkable decrease was observed as described above.

[0042]

As described above, according to the present invention,
It is possible to provide a thermoplastic resin molding intermediate having a long-term durability such as a polyester resin, and it greatly contributes to a wide range of thermoplastic resin molding technology fields.

[Brief description of drawings]

FIG. 1 is a schematic configuration explanatory diagram of an apparatus for manufacturing a thermoplastic resin molding intermediate according to a first embodiment.

FIG. 2 is an explanatory view of the mechanical strength measurement results of the thermoplastic resin molding intermediate of the first example, where (A) shows tensile strength and (B) shows bending strength.

FIG. 3 is an explanatory view of the mechanical strength measurement results of the thermoplastic resin molding intermediate of the second example, where (A) shows tensile strength and (B) shows bending strength.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Kneading extrusion device 2 Kneading cylinder 3 Kneading extrusion screw 4 Kneading extrusion motor 5 Nozzle 6 Heater 7 Material supply device 8 Hopper 9 Air hole 10 Material supply screw 11 Material supply motor 12 Lid body 13 Air hole 14 Heat retention heating element 15 Dry air blower 16 Dry Air Duct 17 Cooling Device 18 Cooling Water Tank 19 Guide Roller 20 Cooling Water 21 Pelletizer 22 Pelletizer Box 23 Rotating Cutter 24 Holding Roller 25 Thermoplastic Resin Molding Intermediate Storage Bag 26 Thermoplastic Resin Powder 27 Thermoplastic Resin Molding Intermediate

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Claims (6)

[Claims] 1. When a thermoplastic resin molding intermediate is produced by heating and melting a thermoplastic resin, and then cooling and molding the thermoplastic resin, the thermoplastic resin is heated before the thermoplastic resin is melted. A method for producing a thermoplastic resin molding intermediate, characterized in that the temperature is maintained in a temperature range of 70 ° C. or higher and 10 ° C. or higher lower than the melting point of the thermoplastic resin. 2. The thermoplastic resin is maintained at a temperature range of 70 ° C. or higher at a temperature lower than the melting point of the thermoplastic resin by 10 ° C. or more, and dry air is supplied to the thermoplastic resin. For producing a molded thermoplastic resin intermediate. 3. The thermoplastic resin molding according to claim 1, wherein dry air heated to a temperature range of 70 ° C. or higher and a temperature range lower than the melting point of the thermoplastic resin by 10 ° C. or more is supplied to the thermoplastic resin. Method for producing intermediate. 4. A thermoplastic resin molding intermediate production apparatus having means for heating and melting a thermoplastic resin and means for cooling and molding the melted thermoplastic resin, wherein the thermoplastic resin is heated. A device for producing a thermoplastic resin molding intermediate, characterized in that it is provided with means for maintaining the temperature of the thermoplastic resin at 70 ° C. or more and 10 ° C. or more lower than the melting point of the thermoplastic resin before melting by melting. . 5. A means for maintaining the temperature of the thermoplastic resin at 70 ° C. or higher in a temperature range lower than the melting point of the thermoplastic resin by 10 ° C. or more, and means for supplying dry air to the thermoplastic resin are provided. The apparatus for manufacturing a thermoplastic resin molding intermediate according to claim 4. 6. The thermoplastic resin according to claim 4, wherein the thermoplastic resin is provided with means for supplying dry air in a temperature range of 70 ° C. or higher and 10 ° C. or lower lower than the melting point of the thermoplastic resin. Equipment for manufacturing resin molding intermediates.