JP2020015252A - Method for manufacturing polyglycolic acid thick injection molded article - Google Patents

Abstract

To provide a method for manufacturing a polyglycolic acid thick injection molded article by suppressing the occurrence of voids and sink marks.SOLUTION: A method for manufacturing a polyglycolic acid thick injection molded article with a 5-150 mm of thickness includes a step for filling a mold provided with a hot runner with a molten resin in 30-1,800 sec. In a step 2, a temperature Tof a tip portion of the hot runner is a temperature of a body portion of the hot runner T+10°C or more. A temperature of the body portion of the hot runner Tis 350°C or less.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a thick injection molded product of polyglycolic acid.

  Thick molded articles of polyglycolic acid have been produced by a solidification extrusion method. In the solidification extrusion method, a molten resin is extruded into a round bar or plate shape through a forming die, and the outer periphery of the cooled and solidified round bar or plate is sandwiched between rollers and pressed to form a molded product with high dimensional accuracy. (Patent Document 1). Although the solidification extrusion method can obtain a molded product with high dimensional accuracy, the shape of the obtained molded product is limited to a simple shape such as a round bar or a plate. Therefore, in order to obtain a molded article having a complicated shape such as unevenness, further processing such as cutting is required.

  Patent Document 2 discloses a method for producing an injection molded product of polyglycolic acid.

International Publication No. WO2014 / 077732 JP-A-10-72529

  The injection molding method is a molding method capable of shaping an arbitrary shape by injecting a molten resin into a mold, and has less loss of material than cutting a solidified extruded product. However, as described in Patent Document 1, when trying to obtain a thick molded product of polyglycolic acid, which is a crystalline resin, by injection molding, heat shrinkage after shaping or shrinkage due to crystallization causes sink marks or voids. There is a problem that occurs. In addition, the thickness of the injection-molded piece manufactured by the manufacturing method disclosed in Patent Document 2 is small, and development of a method for manufacturing a thick injection molded product of polyglycolic acid is desired.

  The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to realize a method for producing a polyglycolic acid thick injection molded article in which generation of voids and sink marks is suppressed.

  The present inventors have conducted intensive studies to solve the above-described problems, and (1) using a hot runner at the time of injection molding of polyglycolic acid, thereby filling the resin into the mold in proportion to the filling time. (2) On the other hand, attention was paid to the fact that polyglycolic acid was thermally decomposed when the temperature of the main body of the hot runner was increased to increase the filling time, (2).

  Then, the present inventors set the temperature of the body of the hot runner higher than the temperature of the manifold of the hot runner in the main body of the hot runner, and heat only the tip portion of the hot runner to thermally decompose the polyglycolic acid. The present invention has been made based on the finding that is suppressed.

That is, the method for producing a thick injection molded article of polyglycolic acid according to the present invention comprises:
A method for producing a polyglycolic acid thick injection molded product having a thickness of 5 to 150 mm,
Step 1 of supplying a resin material containing polyglycolic acid to a molding machine and melting the resin material;
Step 2 of filling the molten resin material into a mold having a hot runner in a time of 30 to 1,800 seconds; and cooling the resin material filled in the mold to form a polyglycolic acid thick injection molded article. Step 3 of obtaining;
Including
In the step 2, the producing temperature T _H2, the tip of the hot runner, and the said hot runner body portion temperature T _{H1 +} 10 ° C. or more,
Wherein the temperature T _H1 of the body portion of the hot runner is 350 ° C. or less, a method for producing a polyglycolic acid thick injection molded product.

  According to the present invention, it is possible to produce a polyglycolic acid thick injection molded article in which the generation of voids and sink marks is suppressed.

The method for producing a thick polyglycolic acid injection molded article according to the present invention is a method for producing a thick polyglycolic acid injection molded article having a thickness of 5 to 150 mm,
Step 1 of supplying a resin material containing polyglycolic acid to a molding machine and melting the resin material;
Step 2 of filling the molten resin material into a mold having a hot runner in a time of 30 to 1,800 seconds; and cooling the resin material filled in the mold to form a polyglycolic acid thick injection molded article. Step 3 of obtaining;
Including
In the step 2, the producing temperature T _H2, the tip of the hot runner, and the said hot runner body portion temperature T _{H1 +} 10 ° C. or more,
Wherein the temperature _{T H1} of the body portion of the hot runner is 350 ° C. or less.

  The thickness of the polyglycolic acid thick injection molded product obtained by the production method according to the present invention is 5 to 150 mm, preferably 6 to 125 mm, and more preferably 7.5 to 100 mm.

[Step 1]
In step 1, a resin material containing polyglycolic acid is supplied to a molding machine to melt the resin material.

<Polyglycolic acid>
Polyglycolic acid used in the present invention (PGA) is (Equation 1) - a polymer containing a repeating unit represented by _{- (- O-CH 2 -CO} -). In the polymer, the proportion of the repeating unit represented by Formula 1 is usually 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, and particularly preferably. It is at least 95% by mass, most preferably at least 99% by mass. If the proportion of the repeating unit represented by (Formula 1) is less than 70% by mass, the toughness, crystallinity, heat resistance, hardness and the like tend to decrease. In many cases, it is most preferable to use a homopolymer of polyglycolic acid in which the proportion of the repeating unit represented by (Formula 1) is 100% by mass.

  Polyglycolic acid can be produced by condensation polymerization of glycolic acid or ring opening polymerization of glycolide. Examples of the repeating unit other than the repeating unit represented by the above (formula 1) include a repeating unit derived from a cyclic monomer such as ethylene oxalate, lactide, lactones, trimethylene carbonate, and 1,3-dioxane. Preferred, but not limited to.

  By introducing a repeating unit derived from a cyclic monomer at a ratio of 1% by mass or more, the melting point of polyglycolic acid can be lowered to lower the processing temperature, thereby reducing thermal decomposition during melt molding and the like. be able to. In addition, the crystallization rate of polyglycolic acid can be controlled by copolymerization to improve melt moldability, for example, extrusion moldability. On the other hand, when the number of repeating units derived from the cyclic monomer is too large, the crystallinity inherent in polyglycolic acid is impaired, and the toughness, heat resistance, and the like of the obtained shaped material or molded article may be significantly reduced. .

  As the polyglycolic acid, those having a weight average molecular weight of usually exceeding 70,000, preferably 100,000 to 500,000, more preferably 120,000 to 450,000, and further preferably 150,000 to 400,000, are used.

The polyglycolic acid preferably has a melt viscosity measured at a temperature of 270 ° C. and a shear rate of 120 sec ⁻¹ of 300 to 2,000 Pa · s, more preferably 450 to 1,600 Pa · s, and 600 More preferably, it is 〜1,400 Pa · s. If the melt viscosity is lower than the lower limit, the mechanical properties of the molded article tend to decrease. On the other hand, if it exceeds the upper limit, the fluidity of the molten resin deteriorates, and when molding a complicated shape, the resin may not be able to be filled in details.

<Resin material>
The resin material used in the present invention is a resin composition containing polyglycolic acid as a main component. The main component means that the content of polyglycolic acid in the resin component is usually 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more. . Other resin components include thermoplastic resins other than polyglycolic acid, for example, other biodegradable resins such as polylactic acid. A resin composition in which the content of polyglycolic acid in the resin component is 100% by mass is of course acceptable.

  The resin material used in the present invention may contain coloring agents such as dyes and pigments. By using the coloring agent, it is possible to obtain a polyglycolic acid thick-walled injection molded product having a high-class feel and easy to perform cutting and the like. As the colorant, a pigment is preferable in terms of excellent heat resistance. As the pigment, pigments having various colors used in the technical field of synthetic resins, such as a yellow pigment, a red pigment, a white pigment, and a black pigment, can be used. Among these pigments, carbon black is particularly preferred. Examples of the carbon black include acetylene black, oil furnace black, thermal black, and channel black.

  The resin material used in the present invention is preferably a polyglycolic acid composition containing 0.001 to 5% by mass of a coloring agent based on the total amount. The content ratio of the colorant is preferably 0.01 to 3% by mass, more preferably 0.05 to 2% by mass. The colorant can be melt-kneaded with the polyglycolic acid, but if necessary, a polyglycolic acid composition (master batch) having a high concentration of the colorant is prepared, and the master batch is diluted with the polyglycolic acid. A resin material having a desired colorant concentration can also be prepared. From the viewpoint of uniform dispersibility of the colorant, it is preferable to prepare a resin material in which polyglycolic acid and the colorant are melt-kneaded and pelletized.

  The resin material used in the present invention may contain a filler for the purpose of improving mechanical strength or heat resistance. As the filler, a fibrous filler or a granular or powdery filler can be used, but a fibrous filler is preferable.

  Examples of the fibrous filler include inorganic fibers such as glass fiber, carbon fiber, asbestos fiber, silica fiber, alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber, and potassium titanate fiber; Metal fibrous materials such as aluminum, titanium, steel, and authenticity; high-melting organic fibrous materials such as polyamide, fluororesin, polyester resin, and acrylic resin; and the like. As the fibrous filler, short fibers having a length of 10 mm or less, more preferably 1 to 6 mm, and still more preferably 1.5 to 4 mm are preferable, and inorganic fibrous materials are preferably used. preferable.

  Granular or powdered fillers include mica, silica, talc, alumina, kaolin, calcium sulfate, calcium carbonate, titanium oxide, ferrite, clay, glass powder, zinc oxide, nickel carbonate, iron oxide, quartz powder, magnesium carbonate, And barium sulfate.

  These fillers can be used alone or in combination of two or more. The filler may be treated with a sizing agent or a surface treatment agent, if necessary. Examples of the sizing agent or surface treatment agent include functional compounds such as epoxy compounds, isocyanate compounds, silane compounds, and titanate compounds. These compounds may be used after subjecting the filler to a surface treatment or a sizing treatment, or may be added simultaneously with the preparation of the resin composition.

  The resin material used in the present invention is preferably a polyglycolic acid composition containing 5 to 70% by mass of a filler based on the total amount. The content ratio of the filler is preferably 10 to 60% by mass, more preferably 15 to 50% by mass, and still more preferably 20 to 40% by mass. The filler can be melt-kneaded with polyglycolic acid, but if necessary, a polyglycolic acid composition (master batch) having a high filler concentration is prepared, and this master batch is diluted with polyglycolic acid. A resin material having a desired filler concentration can also be prepared. From the viewpoint of uniform dispersibility of the filler, it is preferable to prepare a resin material in which polyglycolic acid and the filler are melt-kneaded and pelletized.

  In the resin material used in the present invention, other additives other than those described above include, for example, impact modifiers, resin modifiers, mold corrosion inhibitors such as zinc carbonate and nickel carbonate; lubricants; thermosetting resins; An antioxidant; an ultraviolet absorber; a nucleating agent such as boron nitride; a flame retardant;

<Molding machine>
The molding machine used in the present embodiment is not particularly limited as long as it is an injection molding machine, and the type or scale of the injection molding machine can be appropriately selected according to the shape or size of a target molded product. Similarly, injection molding conditions such as nozzle temperature, injection pressure, injection speed, and holding pressure are appropriately selected according to the type or scale of the injection molding machine to be used.

  In Step 1, the temperature of the cylinder of the molding machine is preferably from Tm ° C to Tm + 80 ° C, more preferably from Tm + 10 ° C to Tm + 65 ° C, and more preferably from Tm + 20 ° C to Tm + 50 ° C. Is more preferable. When the temperature of the cylinder is in the above-mentioned temperature range, there is an effect that thermal decomposition of polyglycolic acid can be suppressed.

  The melting point of polyglycolic acid is 190 to 230 ° C, and varies depending on the molecular weight of polyglycolic acid, the type of comonomer used, additives, and the like.

[Step 2]
In step 2, the molten resin material is filled in a mold having a hot runner for a time of 30 to 1,800 seconds.

  The volume of the mold, the type of the hot runner, the size of the hot runner, and the like are not particularly limited, and can be appropriately selected according to the shape of the molded product.

  Here, if the configuration of the hot runner is described, the configuration of the hot runner differs depending on the manufacturer, but the hot runner body portion mainly composed of the manifold, and the hot runner tip portion mainly composed of the body and the chip Are roughly divided into The molten resin material passes through the flow path in the hot runner body, passes through the tip of the hot runner, and is charged into the mold. The manifolds and nozzles of the hot runner, and the parts corresponding to those of other names, correspond to the hot runner main body. Further, the body, gate chip and gate of the hot runner, and portions corresponding to these, which are referred to by other names, correspond to the tip of the hot runner. Further, even if a special name is not given, the tip of the hot runner body or the nozzle constituting the injection portion to the mold corresponds to the hot runner tip portion here. In the present specification, the “main portion of the hot runner” intends the main portion of the hot runner, and the “tip portion of the hot runner” intends the tip portion of the hot runner.

  In the present embodiment and examples described later, the case where a hot runner having a gate chip is used will be described, and the case where the temperature of the body is referred to as the temperature of the tip of the hot runner will be described. It is not limited to the embodiment.

  The time for filling the molten resin material into the mold is 30 to 1,800 seconds. Within the above-mentioned time range, the volume contracted by crystallization can be compensated for, and sinks and voids can be suppressed.

In the step 2, the producing temperature _{T H2,} the tip of the hot runner is the temperature _T H1 + 10 ° C. or more of the body portion of the hot runner. The temperature _TH2 at the tip is not particularly limited as long as it is within the above-described range, but is preferably a melting point of polyglycolic acid Tm + 10 ° C or higher and Tm + 200 ° C or lower, more preferably Tm + 15 ° C or higher and Tm + 180 ° C or lower, The temperature is more preferably Tm + 20 ° C. or more and Tm + 170 ° C. or less. If the state where the temperature of the distal end portion is high continues, polyglycolic acid is easily decomposed, and a molded article having a desired shape or mechanical properties may not be obtained. If the temperature at the tip is low, the fluidity of the resin tends to be insufficient, and it is difficult to obtain a desired molded product.

  By setting the temperature of the tip portion of the hot runner higher than the temperature of the main body portion of the hot runner, the melt viscosity of the resin material decreases, and the molten resin material can be easily filled in the mold. On the other hand, since the temperature of the main body of the hot runner is lower than the temperature of the tip, the thermal decomposition of polyglycolic acid can be suppressed as compared with the case where the temperature of the entire hot runner is the temperature of the tip. That is, the production method of the present embodiment realizes the suppression of thermal decomposition and the reduction in viscosity by providing a temperature gradient in the hot runner, and a method suitable for injection molding of polyglycolic acid, which easily causes thermal decomposition. Has become.

In the step 2, the temperature _{T H1} of the body portion of the hot runner is at 350 ° C. or less, it is not more than Tm + 80 ° C. melting point Tm-20 ° C. or more polyglycolic acid is preferably, 270 ° C. or less 210 ° C. or higher Is more preferably 215 to 260 ° C. When T _H1 is in the above-mentioned temperature range, it is possible to suppress the thermal decomposition of polyglycolic acid, and it is possible to easily fill the mold with the molten resin material.

Temperature T _H1 of the body portion of the hot runner, for example, can be controlled by a hot runner manifold heater. The temperature of the cylinder of the molding machine and the temperature of the main body of the hot runner may be the same or different.

[Step 3]
In step 3, the resin material filled in the mold is cooled to obtain a polyglycolic acid thick injection molded product.

  In step 3, the temperature of the mold is preferably from 60 to 180 ° C, more preferably from 80 to 160 ° C, and even more preferably from 100 to 150 ° C. When the temperature exceeds the above upper limit temperature range, burrs hardly occur in the polyglycolic acid thick injection molded product.

  In step 3, the cooling time of the mold is preferably 60 to 3,600 seconds.

  According to the present invention, a thick injection product of polyglycolic acid having a void fraction of usually 1.0% or less, preferably 0.8% or less, more preferably 0.5% or less can be obtained.

  For example, as shown in Examples, the void ratio is obtained by observing the inside of a molded product using an X-ray CT apparatus, and calculating the ratio of the volume of the molded product to the volume of the void (void) from the obtained X-ray CT image. Can be obtained by

  Sink refers to a dent generated on the outer surface of a molded product. The occurrence of sink marks can be visually observed. Further, as shown in the examples, a value obtained by subtracting the minimum thickness from the maximum thickness of the molded product can be calculated as the sink mark amount.

By the production method according to the present invention, a polyglycolic acid thick injection molded product having a molecular weight of preferably 11 × 10 ⁴ or more, more preferably 15 × 10 ⁴ or more, and still more preferably 20 × 10 ⁴ or more can be obtained. According to the production method, a polyglycolic acid thick injection molded article in which thermal decomposition is suppressed can be obtained. The molecular weight of polyglycolic acid contained in the polyglycolic acid thick-walled injection molded product obtained by the production method is preferably such that the molecular weight of polyglycolic acid supplied to the molding machine in Step 1 is 100%. It is at least 60%, more preferably at least 65%, further preferably at least 75%, particularly preferably at least 85%.

<Summary>
Step 1 of supplying a resin material containing polyglycolic acid according to the present invention to a molding machine and melting the resin material;
Step 2 of filling the molten resin material into a mold having a hot runner in a time of 30 to 1,800 seconds; and cooling the resin material filled in the mold to form a polyglycolic acid thick injection molded article. Step 3 of obtaining;
Including
In the step 2, the producing temperature T _H2, the tip of the hot runner, and the said hot runner body portion temperature T _{H1 +} 10 ° C. or more,
Wherein the temperature _{T H1} of the body portion of the hot runner is 350 ° C. or less.

In the method for producing a thick injection molded product of polyglycolic acid according to the present invention, the polyglycolic acid preferably has a melt viscosity of 300 to 2000 Pa · s measured at a temperature of 270 ° C. and a shear rate of 120 sec ⁻¹ .

  In step 1 of the method for producing a thick injection molded article of polyglycolic acid according to the present invention, the temperature of the cylinder of the molding machine is preferably not less than Tm ° C and not more than Tm + 80 ° C of melting point of polyglycolic acid.

  In step 3 of the method for producing a thick injection molded article of polyglycolic acid according to the present invention, it is preferable that the temperature of the mold is 60 to 180 ° C and the cooling temperature is 60 to 3,600 seconds.

  Further, it is preferable that the void ratio of the thick polyglycolic acid injection molded product obtained in Step 3 of the method for producing a thick polyglycolic acid injection molded product according to the present invention is 0.5% or less.

  The molecular weight of polyglycolic acid contained in the polyglycolic acid thick injection molded product obtained in Step 3 of the method for producing a polyglycolic acid thick injection molded product according to the present invention is supplied to the molding machine in Step 1. When the molecular weight of the polyglycolic acid is 100%, it is preferably at least 65%.

  Examples will be shown below, and the embodiments of the present invention will be described in more detail. Of course, it is needless to say that the present invention is not limited to the following embodiments of the present invention, and various details can be made. Furthermore, the present invention is not limited to the above-described embodiments, and various changes can be made within the scope shown in the claims, and embodiments obtained by appropriately combining the disclosed technical means are also described. Included in the technical scope of the invention. In addition, all of the documents described in this specification are incorporated by reference.

[Examples 1 and 2 and Comparative Example 1] Production of thick injection molded product of polyglycolic acid Using an injection molding machine (EP5 Real Mini, manufactured by Nissei Plastic Industry Co., Ltd.), length 8 mm x width 8 mm x height An 8 mm thick polyglycolic acid thick injection molded article was produced.

Polyglycolic acid (100R90, molecular weight 24.8 × 10 ⁴ ) manufactured by Kureha Corporation was used. The melt viscosity of polyglycolic acid was measured using polyglycolic acid resin pellets. At a temperature of 270 ° C. and a shear rate of 122 sec ⁻¹ , the melt viscosity measured with a nozzle-equipped capillary (D = 1.0 mm, L = 10 mm) (manufactured by Toyo Seiki Seisaku-sho, Ltd.) was 900 Pa · s.

  The screw diameter of the injection molding machine was 16 mm and the maximum clamping force was 49 kN. A mold having a cavity (length 8 mm × width 8 mm × height 8 mm) for obtaining a desired molded product (block) has a hot runner (manufactured by Seiki Co., Ltd., gate diameter 0.2 mm), and is injection-molded. The mold was filled with the resin material melted by the machine.

  Table 1 shows the setting conditions of the injection molding machine and the hot runner in Examples 1 and 2 and Comparative Example 1. In Table 1, "hot runner temperature" indicates the temperature of the main body and the tip of the hot runner, respectively.

Comparative Example 2 Production of Polyglycolic Acid Thick Injection Molded Product Polyglycolic acid thick injection molded product was produced in the same manner as in Example 2 except that the hot runner was not used and the holding pressure was changed to 160 MPa. Was manufactured.

[Evaluation Example 1] Evaluation of Each Polyglycolic Acid Thick Injection Molded Product The molecular weight, void fraction, and sink mark amount of the polyglycolic acid thick injection molded products obtained in Examples 1-2 and Comparative Examples 1-2 are shown below. It was calculated using the evaluation means shown.

(Measurement of molecular weight)
A 10 mg test piece was cut out from the PGA molded product, dissolved in 10 mL of hexafluoro-2-propanol (HFIP), filtered through a filter having a pore size of 0.2 μm, and the filtrate was injected into a gel permeation chromatography (GPC) device. The molecular weight was measured. GPC used a GPC-104 system manufactured by Shodex, and HFIP dissolved in 5 mM sodium trifluoroacetate was used as an eluent. The molecular weight was estimated as a PMMA-converted value from a calibration curve obtained using standard polymethyl methacrylate (PMMA).

(Calculation of void fraction)
The inside of the injection molded article of polyglycolic acid was observed using an X-ray CT apparatus TUX-3200N (manufactured by Marstoke Solution). The measurement was performed at a tube voltage of 40 to 50 kV and a tube current of 200 μA, and the void ratio was calculated from the volume ratio of the molded product and the void (void) portion from the X-ray CT image.

(Measurement of sink mark)
The sink of the polyglycolic acid injection molded product was measured using a three-dimensional optical profiler system NewView 8300TM series (manufactured by ZYGO Corporation). The measurement location was determined with the vertical and horizontal directions centered on the minimum height of the side of the mold on the gate side and the opposite side (movable side). The value obtained by subtracting the minimum height from the maximum height was calculated as the sink mark amount. The determined sink marks were evaluated as follows.
○ The sink mark amount is less than 50 μm and the appearance of the molded product is good. ○ The sink mark amount is in the range of 50 to 80 μm, and the appearance of the molded product is slightly poor. X The sink mark amount is more than 80 μm and the appearance of the molded product is poor. Table 1 shows the evaluation results of the sink mark amount.

  As shown in Table 1, it was found that the thick injection molded products of polyglycolic acid obtained in Examples 1 and 2 had a low void ratio and suppressed generation of voids. In addition, the evaluation of the amount of sink marks was “○”, indicating that the occurrence of sink marks was also suppressed.

  On the other hand, it was found that the thick injection molded product of polyglycolic acid obtained in Comparative Example 1 did not suppress generation of voids. In addition, the occurrence of sink marks was not so much suppressed.

  The thick injection molded product of polyglycolic acid obtained in Comparative Example 2 did not suppress the generation of voids and the generation of sink marks.

Comparative Example 3 Production of Polyglycolic Acid Thick Injection Molded Product A polyglycolic acid thick injection molded product was produced in the same manner as in Example 1 except that the temperature of the main portion of the hot runner was changed to 370 ° C.

  As a result of measuring the molecular weight of the obtained thick injection molded product of polyglycolic acid, the temperature of the hot runner body was set to be higher than 350 ° C., and the difference from the tip temperature of the hot runner was set to less than 10 ° C. Of the molded product was thermally decomposed.

  The polyglycolic acid thick injection molded product obtained by the method for producing a polyglycolic acid thick injection molded product according to the present invention has a sufficient thickness, high processing accuracy, and secondary processing of various resin parts by machining. It is suitable for molding of molded articles.

Claims (6)

A method for producing a polyglycolic acid thick injection molded product having a thickness of 5 to 150 mm,
Step 1 of supplying a resin material containing polyglycolic acid to a molding machine and melting the resin material;
Step 2 of filling the molten resin material into a mold having a hot runner in a time of 30 to 1,800 seconds; and cooling the resin material filled in the mold to form a polyglycolic acid thick injection molded article. Step 3 of obtaining;
Including
In the step 2, the producing temperature T _H2, the tip of the hot runner, and the said hot runner body portion temperature T _{H1 +} 10 ° C. or more,
Manufacturing method of the temperature T _H1 of the body portion of the hot runner is 350 ° C. or less, polyglycolic acid thick injection molded product. The method for producing a thick injection molded product of polyglycolic acid according to claim 1, wherein the polyglycolic acid has a melt viscosity of 300 to 2,000 Pa · s measured at a temperature of 270 ° C and a shear rate of 120 sec- ¹ .   3. The method for producing a thick injection molded article of polyglycolic acid according to claim 1, wherein, in the step 1, the temperature of the cylinder of the molding machine is not less than Tm ° C. and not more than Tm + 80 ° C. of melting point of polyglycolic acid.   4. The thick polyglycolic acid injection according to claim 1, wherein in the step 3, the temperature of the mold is 60 to 180 ° C., and the cooling time of the mold is 60 to 3,600 seconds. 5. Manufacturing method of molded product.   The production of a thick polyglycolic acid injection molded product according to any one of claims 1 to 4, wherein the void ratio of the polyglycolic acid thick injection molded product obtained in the step 3 is 0.5% or less. Method.   Assuming that the molecular weight of polyglycolic acid supplied to the molding machine in Step 1 is 100%, the molecular weight of polyglycolic acid contained in the thick polyglycolic acid injection molded product obtained in Step 3 is 65% or more. A method for producing a thick injection molded article of polyglycolic acid according to any one of claims 1 to 5.