POLYARYLENETHIOETHER STRETCHED BLOW-MOLDED VESSEL AND PRODUCTION THEREOF

Abstract: A polyarylenethioether stretched blow-molding vessel, obtained by a modified blow molding of a substantially linear polyarylenethioether having a melt viscosity of 3,000 to 20,000 poise [at 310°C, shear rate = 200 sec⁻¹]. The modified blow molding comprises injecting the polymer in a mold to form a bottomed parison, stretching the bottomed parison along its axis by means of a rod or mandrel, and the stretched bottomed parison is then subjected to blow molding whereby the lateral stretching is effected. Contrary to conventional polyarylenethioethers, which have heretofore not been used as such for blow molding, the linear polyarylenethioether of such a high molecular weight that the melt viscosity is 3,000 20,000 poise will produce blow-molded articles endowed with good physical properties inherent in polyarylenethioethers.

Description: BACKGROUND OF THE INVENTION Field of the Art This invention relates to a process for producing a stretched blow molded vessel or stretched heat set blow molded vessel made from a linear polyarylenethioether having a melt viscosity of 3,000 to 20,000 poise. Prior Art Polyarylenethioethers, for example, poly-p-phenylenethioethers, have heat resistance which can stand the heat of steam sterilization and chemical resistance to strong acids, strong alkalis or various organic solvents, and therefore they have been expected to be useful as a material for vessels (bottles, tanks, flasks, etc.) for uses in medicine, for foods and for other various chemicals, if they can be molded into the shape of bottles. However, from the viewpoint of a molding material, polyarylenethioethers available in the prior art involve problems, since if they are poor in linearity of the molecular structure, they can be formed into vessels with difficulty only, or if forcibly given the shapes of bottles, they are too brittle to stand practical use. On the other hand, from the viewpoint of the processing technique, there have been the problems that i) polyarylenethioethers have so great a crystallization rate that they can be molded into stretched bottles only with extreme difficulty, or that ii) if they are processed according to the conventional extrusion blow molding technique, namely the process in which a parison is extruded and subjected to blow molding, drawdown of the parison takes place to a great degree and therefore molding into a vessel with a wall of a uniform cross section can be done only with extreme difficulty. For this reason, except for a multi-layer hollow vessel obtained by extrusion blow molding together with a crystalline polyolefin (Japanese Laid-Open Patent Publication No. 79233/1980), polyarylenethioethers have not generally been used as such as the resin for hollow vessels. According to EP-A-0036844 the technical problem of avoiding a high amount of waste material typical for the extrusion method is solved by using a two-step process, the first step being performed in an extruder, thereby preforming a parison which is then further processed in a blow molding machine. It is specifically stated that no injection molding machine is needed. No mention is made of any specific material to be processed in that way and especially the linear polyarylenethioethers having a high molecular weight are not envisaged as molding material. EP-A-008481 refers to an apparatus for the longitudinal stretching of parisons consisting of thermoplastic material and does not disclose any specific working conditions suitable for processing such linear polyarylenethioethers either. SUMMARY OF THE INVENTION The present inventors have carried out intensive studies in order to solve these problems and consequently found that a stretched blow molded vessel of a polyarylenethioether can be obtained by use of a polyarylenethioether of a linear structure having a melt viscosity of 3,000 to 20,000 poise as the starting material and carrying out a combination of injection and strech blowing under specific conditions. More specifically, the process for producing the polyarylenethioether stretched blow-molded vessel according to the invention comprises injecting a substantially linear polyarylenethioether having a melt viscosity of 300 to 2,000 Pa.s (3000 to 20,000 poise) measured at 310°C and a shear rate of 200 s⁻¹ into a mold of 0 to 130°C to form a bottomed parison with an opening at an opposite end, pushing a mandrel or rod into said bottomed parison through the opening thereof to stretch the parison at a resin temperature of 80 to 150°C in the longitudinal direction to 1.5 to 6-fold and subsequently blowing a gas into the parison at a resin temperature of 90 to 180°C within a mold for formation of a vessel to stretch the parison in the lateral direction to 1.5 to 6-fold. In the present invention, by use as a molding resin of a polyarylenethioether which has a certain greatness of molecular weight (300 to 2,000 Pa.s, or 3,000 to 20,000 poise, in terms of melt viscosity) and is substantially linear, physical properties and processability as a hollow vessel can be satisfied and, by employment of a process, in which a bottomed parison is previously molded by injection molding, and the parison is thereafter stretched first in the longitudinal direction with a rod and then in the lateral direction by blowing of a gas, a stretched hollow vessel can be produced with ease without suffering from the drawdown of the parison. The hollow vessel thus obtained is transparent and tough, and also excellent in heat resistance and chemical resistance. BRIEF DESCRIPTION OF THE DRAWINGS In the accomp;anying drawings: Figs. 1(a), (b) and (c) are a sectional view showing the molds used in the production of a stretched blow-molded vessel in accordance with the present invention, wherein Fig. 1(a) shows injection molding for producing a bottomed parison, Fig. 1(b) stretching the bottomed parison, and Fig. 1(c) blow-molding of the stretched parison. DETAILED DESCRIPTION OF THE INVENTION Molding Material The molding material used in the process of the present invention is a polymer having a structure of a polyarylenethioether (-Ar-S-) n (Ar: arylene group). The polyarylenethioether polymer may preferably comprise p-phenylene group as the arylene group or p-phenylene group as the main component of the arylene group in view of heat resistance and moldability of the polymer. Other arylene groups than p-phenylene group may include: m-phenylene group alkyl-substituted phenylene group (R: alkyl group, preferably a lower alkyl; n: an integer of 1 to 4), p,p'-di-phenylenesulfone group p,p'-biphenylene group p,p'-diphenyleneether group naphthalene group as useful ones. Also, a block copolymer containing p-phenylene group as the main component, for example, a block copolymer containing 95 to 70 mol% of the recurring units of in a block and 5 to 30 mol % of m-phenylene groups in a block in the chain (as disclosed in Japanese Patent Application No. 134633/1984) is more excellent in stretched blow moldability than poly-p-phenylenesulfide homopolymers (PPPS) and yet has mechanical properties, etc. substantially comparable to PPPS, thus being more excellent than PPPS, and therefore particularly preferable. The molding material to be used in the present invention has the above chemical structure, and is also a substantially linear polyarylenethioether having a melt viscosity of 300 to 2,000 Pa.s (3,000 to 20,000 poise) (measured at 310°C, shear rate = 200 sec⁻¹), particularly preferably 400 to 1,500 Pas (4,000 to 15,000 poise). With a polymer having a low melt viscosity of less than 300 Pas (3,000 poise), the thickness of a wall of the vessel may be nonuniform and breaking may occur at the thin portion, whereby stretched blowing can be done only with difficulty, or even if stretched blow molding may be possible, the resultant product is undesirably mechanically fragile. On the other hand, in the case of a polymer having a high melt viscosity in excess of 2,000 Pas (20,000 poise), the melt resin can be filled to the tip portion only with difficulty during molding of a bottomed parison by injection, whereby the thickness tends to become also undesirably nonuniform. Further, the polyarylenethioether to be used in the present invention is required to be substantially linear. For example, a crosslinked polymer obtained by crosslinking polymerization with the use of as much as 0.1 mole or more of a crosslinking agent such as tri- or tetrachlorobenzene per 100 mols of arylene groups during polymerization, or a polymer crosslinked by high temperature treatment of the polymer in the presence of O₂ thereby having an apparent melt viscosity increased to two-fold or more is not preferable for the present invention. These crosslinked polymers are not preferable for the reason that stretched blow moldability is very poor during stretching blowing, or because of insufficient mechanical strength of the molded vessel, even if stretching blowing can be effected. Besides, the polymers crosslinked by high temperature treatment and thereby having their visvosity increased are excessively colored whereby stretched blow molded products of poor transparency will be produced. The linear polyarylenethioether satisfying the conditions of the resin to be used in the present invention as described above can be prepared according to, for example, the two-step polymerization process wherein some quantity of water is added thereto, etc. by the present inventors in the pending patent application filed (Japanese Patent Application No. 126725/1984). The polyarylenethioether as described above can be preferably used as such, but within the limit wherein no trouble is brought about in stretched blow molding, it is also possible to add inorganic fillers (silica powder, alumina powder, silica-alumina powder, mica, kaolin, calcium carbonate powder, calcium silicate powder, talc, carbon black, wollastonite, potassium titanate whisker, etc.), fibrous fillers (glass fiber, carbon fiber, etc.), crystalline nucleating agents, crystallization controllers, pigments, stabilizers, lubricants, mold release agents, etc. also, so long as no trouble is caused in stretching blow molding, it is possible to use polyarylenethioethers with different chemical structures or other thermoplastic resins blended in the resin of the present invention. Injection and Stretching (and Heat Set) Blow Molding Blow molding generally comprises extruding a thermoplastic resin as a parison through an extruder, then inserting said parison into an open mold (comprising a pair of mating mold halves), closing both the mold halves to seal the ends of the parison, and at the same time blowing a high pressure gas through the opening portion to inflate the parison, thereby obtaining a vessel with a contour which is the same as the inner surface shape of the mold. However, the polyarylenethioether used as the molding material has a great fluidity during melting and yet a small viscoelastic property, whereby the drawdown is great and therefore molding according to the known process of "parison extrusion" and then "blow molding" can be done with difficulty only. The present invention, in skillful utilization of the very high fluidity of a polyarylenethioether, purports to melt the resin by heating to its melting point or higher and form a bottomed parison according to the injection molding method instead. During this process step, the injection mold temperature is maintained at 0 to 130°C, preferably 20 to 110°C. At a temperature lower than 0°C, it will take too long a time before heating to the stretching and blowing temperature in the stretching blow step, which is not desirable from the standpoint of productivity. On the other hand, at a temperature exceeding 130°C, the bottomed parison tends to crystallize, whereby stretching cannot be effected sufficiently in the stretching step. After injection of the bottomed parison, the longitudinal stretching step is performed. The bottomed parison obtained is fixed at the opening portion, and a mandrel or rod is pushed into the parison from the opening portion to effect stretching in the longitudinal (axial) direction. The stretching ratio shall be within the range from 1.5 to 6-fold, particularly from 2 to 5-fold of the original length. At a stretching ratio below 1.5-fold, molecular orientation is insufficient and therefore tough vessels can be obtained only with difficulty. On the other hand, at a stretching ratio in excess of 6-fold, the bottom of the parison may be undesirably broken. The resin temperature of the parison during stretching shall be within the range from 80 to 150°C and, for that purpose, the parison can be preheated or the rod may be heated. At a temperature lower than 80°C, stretching can be done only with difficulty, while at a temperature exceeding 150°C, tough vessels can be obtained also only with difficulty, because the thus obtained molecular orientation is insufficient even when stretched. The next step following the longitudinal stretching is the lateral stretching step, namely the blowing step. The longitudinally stretched tube is placed between mating halves of a mold for formation of a vessel, and a high pressure gas is blown thereinto, thereby effecting lateral stretching until the resin is pushed against the inner walls of said mold. The stretching ratio shall be within the range from 1.5 to 6-fold, particularly from 2 to 5-fold of the original length of the tube wall. At a stretching ratio lower than 1.5-fold, the molecular orientation is insufficient, whereby tough and highly transparent vessels can be obtained only with difficulty. On the other hand, at a ratio exceeding 6-fold, the parison may be broken during blowing. The resin temperature during blowing shall be within the range from 90 to 180°C and, for that purpose, the tube can be pre-heated or the blowing gas can be heated up to 180°C. At a resin temperature, lower than 90°C, stretching can be done with difficulty only, while at a temperature exceeding 180°C, tough and highly transparent vessels can be obtained only with difficulty, because molecular orientation is insufficient even if stretched. The blow-molded vessel thus subjected to longitudinal and lateral stretching is a transparent and tough vessel, and also excellent in heat resistance and chemical resistance. However, in the case when a still higher heat resistance is demanded, it is preferable to heat set in the stretched state. That is, heat setting is effected by maintaining the vessel stretched longitudinally and laterally at a temperature of 150 to 260°C for 1 second to 60 minutes. At a temperature lower than 150°C, it will take a long time for heat setting, which is disadvantageous with respect to productivity, while the resin may be undesirably subject to melting at a temperature over 260°C. With a time shorter than 1 second, no satisfactory heat setting can be obtained, while a time over 60 minutes is disadvantageous as regards productivity. Heating may be conducted according to any desired method, but it is preferable to blow a high temperature gas from the opening portion of the molded vessel. Also, in the case of effecting heat setting within the mold, the mold may be heated, simultaneously with the blowing of a high temperature gas into the vessel in the mold. After heat setting the vessel produced is cooled to a temperature of 150°C or lower. Cooling may be done according to any desired method, but it is preferable to perform cooling by blowing a cooling gas of a temperature lower than 150°C from the opening portion of said vessel. Having described above about the basic or typical embodiment of the process of the present invention, it would be apparent to those skilled in the art that various modifications other than this embodiment are possible. Accordingly, for example, the longitudinal, stretching step can be performed within the mold for formation of a vessel, and lateral stretching can be done after or simultaneously with longitudinal stretching. Also, it is preferable with respect to productivity to practice lateral stretching and heat setting within the same mold. The mold or mandrel rod to be used for injection molding, longitudinal stretching, lateral stretching and heat setting may be applied with a mold release agent such as of a silicone or a fluorinated product for easy releasing of the molded product from the mold. Further, mold release can be done with ease, if a small amount of a mold release agent is mixed into the resin. Figs. 1(a) through (c) illustrate the procedure. In Fig. 1(a), a molten, mass of a resin is injected into a mold 1 by means of an injection machine 2 whereby a bottomed parison 3 is formed. In Fig. 1(b), the bottomed parison is placed in a mold 4 and stretched along its axis by means of a mandrel or bar 5 whereby a stretched bottomed parison 6 is formed. In Fig. 1(c), the stretched bottomed parison is placed in mating mold halves 7 and a gas 8 is introduced into the parison to inflate the parison to assume the shape defined by the inner surface of the mold halves whereby a stretched blow-molded vessel 9 is produced. Vessel Produced The stretched blow-molded product of the polyarylenethioether produced according to the present invention (bottle, tank, flask, etc.) is excellent in heat resistance, tpughness and chemical resistance. Also, it has the important specific feature that it can be formed into a transparent article. The blow-molded product produced according to the present invention, which can be boiled or steam sterilized and is also transparent, would be useful for medical purposes and for the handling of food. Further, since the product according to the present invention is excellent in heat resistance and chemical resistance, it is useful for vessels to be used at higher temperatures and vessels for containing strong acids, strong alkalis or organic solvents. EXPERIMENTAL EXAMPLES Synthesis examples (1) A 20-liter titanium-lined polymerization autoclave was charged with 11.0 kg of NMP (N-methylpyrrolidone) and 20.0 mols of Na₂S·5H₂O, and the mixture was heated up to about 200°C to distill off water (the sulfur content lost during the distillation discharged as H₂S was 1.4 mol% of the Na₂S·5H₂O charged; the residual water content in the autoclave: 28 mols). Next, 20 mols of P-DCB (p-dichlorobenzene) and 3 kg of NMP were charged and, after replacement of the inside of the autoclave with N₂, polymerization was carried out at 220°C for 3 hours, and further the reaction was continued with addition of 54 mols of water at 255°C for 0.5 hour to prepare a reaction mixture (C-1), which was withdrawn from the autoclave and stored. A small amount of the (C-1) mixture was sampled and the polymerization degree of the p-phenylenesulfide polymer was measured (by the fluorescent X-ray method) to be 270. The polymer produced was stored as a prepolymer for the further polymerization. A 20-liter titanium-lined polymerization autoclave was charged with 11.0 kg of NMP and 20.0 mols of Na₂S· 5H₂O, and the mixture was heated up to about 200°C to distill off water (S content loss = 1.4 mol% of the Na₂S· 5H₂O charged; the residual water content in the autoclave: 27 mols). Then, 20 mols of m-DCB (metadichlorobenzene) and 3 kg of NMP were charged and, after replacement of the atmosphere with N₂, polymerization was carried out at 210°C for 12 hours, and further the reaction was continued with addition of 52 mols of water at 250°C for 0.5 hours to prepare a reaction mixture (D-1), which was withdrawn from the autoclave and stored. A small amount of the (D-1) mixture was sampled and the polymerization degree of the m-phenylenesulfide polymer was measured (by the GPD method) to be 90. The polymer produced was stored as a prepolymer for the further polymerization. A 20-liter titanium-lined polymerization autoclave was charged with 14350 g of the (C-1) mixture, 2400 g of the (D-1) mixture and 130 g of water, and the mixture was heated at 260°C for 4 hours to react the two types of the prepolymers into a block copolymer. After the reaction, the block copolymer thus produced was recovered from the reaction mixture. Additional five batches of polymerization were further carried out according to the same method, and six batches of the polymer were blended uniformly to prepare a block polymer (T-1). The block polymer T1 was found by the FT-IR method to have a composition of units of 14/86 (mol/mol), with melt viscosity being 5,100 poise (at 310°C, shear rate = 200 s⁻¹). (2) A 20-liter titanium-lined polymerization autoclave was charged with 11.0 kg of NMP and 20.0 mols of Na₂S·5H₂O, and the mixture was heated up to about 200°C to distill off water (S content loss discharged as H₂S was 1.3 mol% of the Na₂S·5H₂O charged; the residual water content in the autoclave: 25 mols). Next, 20 mols of P-DCB and 3 kg of NMP were charged and, after replacement of the inside of the autoclave with N₂, polymerization was carried out at 210°C for 5 hours, and further the reaction was continued with addition of 52 mols of water at 250°C for 0.5 hours to prepare a reaction mixture (C-2), which was withdrawn from the autoclave and stored. A small amount of the (C-2) mixture was sampled and the polymerization degree of the p-phenylenesulfide polymer, a prepolymer, was measured (by the fluorescent X-ray method) to be 220. A 20-liter titanium-lined polymerization autoclave was charged with 11.0 kg of NMP and 20.0 mols of Na₂S· 5H₂O, and the mixture was heated up to about 200°C to distill off water (S content loss = 1.6 mol% of the Na₂S· 5H₂O charged; the residual water content in the autoclave: 28 mols). Then, 20 mols of m-DCB and 3 kg of NMP were charged and, after replacement of the inside of the autoclave with N₂, polymerization was carried out at 210°C for 7 hours, and further the reaction was continued with addition of 53 mols of water at 240°C for 0.5 hours to prepare a reaction mixture (D-2), which was withdrawn from the autoclave and stored. A small amount of the (D-2) mixture was sampled and the polymerization degree of the m-phenylenesulfide polymer, a prepolymer, was measured (by the GPC method) to be 40. A 20-liter titanium-lined polymerization autoclave was charged with 14400 g of the (C-2) mixture, 2420 g of the (D-2) mixture and 110 g of water, and the mixture was heated at 255°C for 4 hours to react the two types of the prepolymers into a block copolymer. After the reaction, the block polymer produced was recovered from the reaction mixture. Additional one batch of polymerization was further carried out according to the same procedure, and two batches of the polymer were blended uniformly to prepared a block polymer (T-2). The block polymer T-2 was found by the FT-IR method to have a composition of units of 88/12 (mol/mol), with melt viscosity being 3,500 poise. (3) A 20-liter titanium-lined autoclave was charged with 11.0 kg of NMP, 20.0 mols of Na₂S·5H₂O, and the mixture was heated under N₂ atmosphere over about 1.5 hours up to 200°C to distill off water, 1.55 kg of NMP and 0.45 mols of H₂S (residual water content in the autoclave: 29.4 mols). The mixture was cooled to 130°C, 19.5 mols of P-DCB and 3.0 kg of NMP were added, and polymerization was carried out at 210°C for 6 hours. Then, 70.6 mols of water were additionally charged into the polymerization system to increase the water content in the system, and polymerization was further carried out at 270°C for 10 hours. After polymerization, the polymer was separated by filtration from the reaction mixture, neutralized with dil. hydrochloric acid, washed with water and dried to obtain a poly-p-phenylenethioether (PPPS) T-3. The PPPS T-3 was found to have a melt viscosity of 1,250 Pas (12,500 poise). (4) A 20-liter stainless steel autoclave was charged with 11.0 kg of NMP and 20.0 mols of Na₂S·5H₂O, and the mixture was heated under N₂ atmosphere over about one hour up to 200°C to distill off water, 1.50 kg of NMP and 0.44 mols of H₂S (residual water content in the autoclave: 29.9 mols). The mixture was cooled to 130°C, 19.5 mols of P-DCB and 3.1 kg of NMP were added, and polymerization was carried out at 215°C for 10 hours. The polymer was separatd by filtration from the polymerized slurry, neutralized with hydrochloric acid, washed with water and dried to obtain a poly-p-phenylenethioether. Additional two batches of polymerization were further carried out according to the same procedure, and the polymers obtained (3 batches) were uniformly blended to obtain a poly-p-phenylenethioether (PPPS) T-4. The PPPS T-4 was found to have a melt viscosity of 110 Pas (1,100 poise). (5) According to the same procedure as (4) except for using a mixture of 19.45 mols of P-DCB and 0.05 mols of 1,2,4-trichlorobenzene (crosslinking agent) in place of 19.5 mols of P-DCB and controlling the residual water content in the autoclave to 38 mols, polymerization was carried out to obtain a poly-p-phenylenethioether T-5. The crosslinked polymer T-5 thus produced was found to have a melt viscosity of 530 Pa.s (5,300 poise). (6) A part of the powder of PPPS T-4 was crosslinked by subjecting it to a heat treatment at 250°C in the air for 5 hours. The heat-crosslinked polymer T6 was found to have a melt viscosity of 580 Pas (5,800 Poise). (7) An autoclave was charged with 10 mols of the PPPS T4, 40 g of sodium ethylate, 12 kg of NMP and 110 mols of water, and the reaction was carried out at 265°C for 3.5 hours to obtain a poly-p-phenylenethioether T-7. The linear polymer obtained was found to have a melt viscosity of 31,000 poise. Molding examples 1 - 5 and Comparative molding examples 1 - 9 The polyarylenethioether samples of T-1 - T-7 obtained were pelleted by a pelletizer and molded into bottles with a volume of 500 ml, resin amount of 31 - 33 g and barrel length of 18 cm. (1) Molding was performed according to the process of the present invention, namely the process of forming of a bottomed parison by injection molding → stretching blow molding. The molding conditions in the respective processing steps and their evaluation results are shown in Table 1. (2) In the respective steps of processing, when the breaking ratio exceeded 50% in the processing, indicated with a symbol (-), processing in the subsequent steps were intermitted. When the breaking ratio was 50% or lower in the processing, indicated by a symbol (+), processing was proceeded to the next step for further testing. (3) For heat resistant test of the stretched blow-molded products with 50% or less of breaking ratio in the respective steps, boiling test and high pressure steam sterilization test were conducted. Those deformed by boiling test were rated as (-) and those without deformation as (+). Those without deformation in both boiling test and high pressure steam sterilization test were rated as (++). The boiling test was conducted by heating a sample in boiling water for 30 minutes, and the high pressure steam sterilization test by heating a sample in high pressure steam at 150°C for 30 minutes. The breaking ratio of molded product was measured by permitting a bottle filled with water to fall from a height of 30 cm, and the breaking ratio of 50% or higher was evaluated as (-). Transparency was evaluated by rating devitrification with formation of coarse spherical crystals as (-). The results are summarized in Table 1. In Examples 1 to 5, stretching blowing could be successfully effected and the vessels obtained had also excellent physical properties. In Comparative Example 1, the resin used had too low a viscosity and therefore stretch breakage occurred due to shortage in strength. In Comparative Example 2, the resin had too high a polymerization degree and therefore lateral stretching was difficult even at an elevated stretching temperature. On the other hand, in Comparative Examples 3 and 4, stretching was poorly effected because of the molding materials being crosslinked. In Comparative Example 5, too high a temperature of the mold gave rise to formation of spherule crystals, resulting in poor stretching. In Comparative Example 6, lateral stretching was difficult due to excessive longitudinal stretching. In Comparative Example 7, since longitudinal stretching was done at a temperature lower than Tg, the stretching was difficult. In Comparative Example 8, breaking occurred due to excessive lateral stretching. In Comparative Example 9, stretching was impossible due to low lateral stretching temperature. For these reasons, in any of the Comparative examples, the breaking ratio during processing was 50% or higher. Comparative molding example 10 Molding test was attempted for blow molding of a bottle with the same shape as mentioned above according to the prior art molding process in place of the process of the present invention, namely by forming a parison by extrusion molding, inserting it into a cooled mold, sealing the ends of the parison by closing both halves of the mold and blowing high pressure gas into the parison. Due to too great a drawdown of the parison, the parison was elongated to give no product with sufficient thickness, and therefore most of the products were broken during blowing.

Claims: A process for producing a polyarylenethioether stretched blow-molded vessel, which comprises injecting a substantially linear polyarylenethioether having a melt viscosity of 300 to 2,000 Pas (3,000 to 20,000 poise) measured at 310°C and a shear rate of 200 sec⁻¹ into a mold of 0 to 130°C to form a bottomed parison with an opening at an opposite end, pushing a rod into said bottomed parison through the opening thereof to stretch the parison at a resin temperature of 80 to 150°C in the longitudinal direction to 1.5 to 6-fold and subsequently blowing a gas into the parison at a resin temperature of 90 to 180°C within a mold for formation of a vessel to stretch the parison in the lateral direction to 1.5 to 6-fold. A process for producing a stretched blow-molded vessel according to Claim 1, wherein the stretched blow molded vessel obtained by stretching a bottomed parison in longitudinal and lateral directions is maintained at a temperature of 150 to 260°C for 1 second to 60 minutes to effect heat setting thereof. A process for producing a stretched blow-molded vessel according to Claim 1 or Claim 2, wherein the polyarylenethioether is a substantially linear poly-p-phenylenethioether. A process for producing a stretched blow-molded vessel according to Claim 1 or Claim 2, wherein the polyarylenethioether is a block copolymer comprising 70 to 95 mol% of the recurring units of in a block and 5 to 30 mol% of the recurring units of in a block. A process for producing a stretched blow-molded vessel according to any one of Claim 1 to Claim 2, wherein the polyarylenethioether has a melt viscosity of 400 to 1,500 Pas (4,000 to 15,000 poise).

Inventors: IIZUKA, YO, IWASAKI, TAKAO, KATTO, TAKAYUKI, KOUYAMA, TOSHITAKA, SHIIKI, ZENYA
Applicants: KUREHA KAGAKU KOGYO KABUSHIKI KAISHA
Application year: 1986
Main classification: B29C49
IPC codes: C08G75, B29C49, B65D1, B29K81, B29L22