Method for manufacturing a hollow molded article and hollow molded article obtained therefrom

Abstract

The present invention relates to a method for manufacturing a hollow molded article, which includes manufacturing the hollow molded article by fluid-assisted injection molding, and the method includes the following steps: Step (1): Injecting a molten resin composition into a mold having a mold cavity (1) and at least one overflow cavity (4), where the mold cavity (1) includes a mold main pipe (2) and a plurality of mold branch portions (6), the mold main pipe (2) has an inflection point (i) where the variation tendency of its major axis changes, the major axis is the longer axis of each cross-section of the mold main pipe (2) along its length direction, or when the major axes have the same length, it has a joining point (ii) of the mold main pipe (2) and the nearest mold branch portion (6); Step (2): Injecting a fluid into the molten resin composition through a fluid inlet (5) to obtain the molded article, the fluid inlet (5) is located inside the mold main pipe (2), and the distance LF from the fluid inlet (5) to a plane D0 is at least 1 / 2 of the distance L2 from the plane D0 to the end of the longest mold branch portion (6), the plane D0 is a plane where the inflection joint is located and is perpendicular to the length direction of the mold main pipe (2); Step (3): Demolding the molded article, where the molded article is integrally formed and has a main pipe at one end and a plurality of branch portions at the other end, the branch portions are connected to the main pipe, and here, the molded article is made of a semi-aromatic polyamide resin composition. Further, the present invention relates to a hollow molded article obtained by the above method.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a hollow molded article and a hollow molded article obtained by the method.

[0002] Background A dipping mold is a component used to shape dipped products, such as rubber gloves, by dipping molding. In dipping molding, the dipping mold is immersed in a polymer emulsion, and the polymer particles in the emulsion coalesce on the dipping mold and form a polymer film. Then, the mold is removed from the emulsion, leaving a uniform deposit on the mold. If desired, the thickness of the deposit can be increased by repeating the dipping. After the dipped product is formed, it can be leached, vulcanized, dried, and then demolded.

[0003] Metals, especially aluminum, as well as ceramics or glass, are traditionally used to manufacture such molds. However, metals have the disadvantages of being easily oxidized, not resistant to corrosive components such as acids, poor wear resistance, and a short service life. On the other hand, ceramics and glass are brittle and cannot withstand thermal and mechanical shocks, which can be dangerous for operators when they break. Moreover, the large weight of metal, ceramic, or glass molds means that high energy consumption is required in the manufacture of molded articles.

[0004] The dipping mold is required to have a low weight and a long service life in order to provide cost-effectiveness.

[0005] There have been some attempts by glove mold companies and plastic suppliers to solve the above problems and provide a solution using plastics that have an appearance comparable to that of metals, ceramics, or glass but are lightweight.

[0006] For example, Chinese Patent Application Publication No. 107053564 (CN107053564A) discloses a method for manufacturing a plastic glove forming mold. The method includes injection molding the upper casing and the lower casing of the glove forming mold respectively, and then welding them to form a complete glove forming mold. Further, Chinese Utility Model No. 206066990 (CN 206066990U) discloses a glove dipping forming mold made of glass fiber reinforced polyamide 4T and formed by welding different parts or halves together. Both of the above-mentioned forming molds are not integral and need to be welded to form the whole, which increases the cost and is also prone to damage during use.

[0007] International Publication No. 2020 / 260456 (WO2020260456A1) describes a glove forming mold for latex dipping. The glove forming mold is integral on its surface and is formed by an injection molding or blow molding method. In International Publication No. 2020 / 260456 (WO2020260456A1), the forming mold includes a core-shell structure, and it is necessary to manufacture the two parts by separate molding methods. The glove forming mold is manufactured by a method including injecting or blow molding a first material into a first cavity to manufacture the core; transferring the formed core into a second cavity; and injecting a second material into the second cavity to overmold the formed core. Its complex design causes challenges in the molding method, such as the difficulty of retracting the core part. However, no solutions are mentioned.

[0008] Chinese Patent Application Publication No. 108099067 (CN108099067A) discloses a method for integrally forming a plastic glove forming mold. The method includes molding the glove forming mold in an injection molding machine connected to a nitrogen production facility. However, the technical design regarding the fluid inlet and the overflow cavity is not described. Further, only fluoroplastics are used to mold the glove forming mold.

[0009] Selective solution using plastic has been tried to replace the ceramic for the mold from the above prior art, which poses some technical challenges, for example, a). The complex geometric shape of the mold including undercuts increases the difficulty of demolding when using injection molding; b). The two-step manufacturing method increases the total manufacturing cost and deteriorates its reproducibility, for example, unstable welding performance; c). The one-step manufacturing method, such as liquid-assisted molding, cannot achieve a good surface and uniform part thickness; d). Standard plastics cannot meet the requirements of long-term chemical resistance during the cleaning and washing steps.

[0010] Summary The object of the present invention is to overcome at least one of the above problems of the prior art, and the hollow molded article has a smooth and flat surface appearance, but is lightweight compared to metal or ceramic molded articles, and can withstand mechanical operations and chemical exposures at high temperatures for a long time. It is to provide a method for manufacturing a hollow molded article and an integral hollow molded article.

[0011] The above object is achieved by a method for manufacturing the hollow molded article, which includes manufacturing the hollow molded article by fluid-assisted injection molding.

[0012] The above object is also achieved by a hollow molded article that is integral and has a main pipe at one end and a plurality of branch parts at the other end, where the molded article is made of a semi-aromatic polyamide resin composition.

[0013] The molded article is integral. In the context of the present invention, the term "integral" means that the molded article itself is integrally formed without joining different parts, such as welding, fusing, or assembling, during its manufacture.

[0014] The term "distance" is the perpendicular dimension from a point to a plane.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

[0016] Detailed Description Method for Manufacturing a Molded Article In one aspect, the present invention relates to a method for manufacturing a hollow molded article, which includes manufacturing the molded article by fluid-assisted injection molding (FAIM), and the method includes the following steps: (1) Injecting a molten resin composition into a mold having a mold cavity 1 and at least one overflow cavity 4, where the mold cavity 1 includes a mold main pipe 2 and a plurality of mold branch parts 6 connected to the mold main pipe 2, the resin composition is a semi-aromatic polyamide resin composition, the mold main pipe 2 has an inflection point (i) where the variation tendency of its major axis changes, the major axis is the longer axis of each cross-section of the mold main pipe 2 along its length direction, or when the major axes have the same length, it has a joint point (ii) between the mold main pipe 2 and the closest mold branch part 6, (2) Injecting a fluid into the molten resin composition through a fluid inlet 5 to obtain the molded article, the fluid inlet 5 is located inside the mold main pipe 2, and the distance LF from the fluid inlet 5 to a plane D0 is at least 1 / 2 of the distance L2 from the plane D0 to the end of the longest mold branch part 6, the plane D0 is a plane where its inflection joint is located and is perpendicular to the length direction of the mold main pipe 2, (3) Demolding the molded article, where the molded article is integral and has a main pipe at one end and a plurality of branch parts at the other end, the branch parts are connected to the main pipe, and here, the molded article is made of a semi-aromatic polyamide resin composition.

[0017] The mold main pipe 2 may have a major axis that is constant in its longitudinal direction, or may have a major axis that varies in its longitudinal direction. For example, from the opening of the mold main pipe 2 to the position where the mold branch portion is located, it may have a plurality of different major axes. Preferably, the mold main pipe 2 has a major axis that varies in its longitudinal direction.

[0018] When the major axis of the cross-section of the mold main pipe 2 has different lengths, the inflection point means a point where the variation tendency of the major axis of each cross-section along the longitudinal direction of the mold main pipe 2 changes. For example, when viewed from the opening, before the inflection point, the major axis of the mold main pipe 2 changes from large to small, while after the point, the major axis of the mold main pipe 2 changes from small to large. The “before” and “after” are used only to present their relative positions and are not used to define the detailed positions. The major axis corresponds to the diameter when the cross-section of the mold main pipe 2 is circular.

[0019] When the major axis of the cross-section of the mold main pipe 2 has the same length, the inflection point means the joining point between the mold main pipe 2 and the closest mold branch portion 6.

[0020] The plane D0 is a preset plane on which the inflection point is located and is perpendicular to the longitudinal direction of the mold main pipe 2. When there are more than one inflection points in the longitudinal direction of the mold main pipe 2, all the planes that satisfy the requirements of the plane D0 may be the plane D0. The plane including the inflection point farthest from the mold branch portion 6 is the preferred plane D0.

[0021] In the conventional FAIM, it is difficult to completely fill the individual mold branch portions with the resin composition or to manufacture its wall thickness uniformly. However, in the present invention, it has surprisingly been found that when a suitable position of the fluid inlet 5 is selected, it is possible to fill the individual mold branch portions with the resin composition and to obtain a molded product having a uniform wall thickness and length.

[0022] Specifically, the fluid inlet 5 is located inside the mold main pipe 2 (the mold main pipe 2 corresponds to the main pipe of the molded product), and the distance LF from the position of the fluid inlet 5 to the plane D0 is 1 / 2 or more of the distance L2 from the plane D0 to the end of the longest mold branch 6 (corresponding to the tip of the middle finger when the molded product of the present invention is a glove molding die), that is, LF≧1 / 2L2.

[0023] In a preferred embodiment, the distance LF is 5 times or less, preferably 3 times or less of L2.

[0024] The molded product may have 2 to 100, preferably 2 to 50, more preferably 2 to 20, and most preferably 3 to 6 branch portions. The branch portions may have the same or different lengths, preferably different lengths.

[0025] The wall thickness of the molded product can be adjusted as needed and may be, for example, 2 to 8 mm, preferably 2 to 5 mm, more preferably 3 to 4 mm.

[0026] The main pipe of the hollow molded product has an opening at the end away from the joint with the branch portion. The diameter of the opening may be the same as or slightly smaller than the end of the main pipe.

[0027] In the FAIM of the present invention, a mold having a mold cavity 1 with a shape corresponding to the hollow molded product is used. In particular, the mold cavity 1 includes a mold main pipe 2 corresponding to the main pipe of the molded product and a mold branch 6 corresponding to the branch portion of the molded product.

[0028] In the FAIM method, the molten semi-aromatic polyamide resin composition is injected into the mold cavity 1 through the resin inlet 3, and then a fluid is injected into the resin composition through the fluid inlet 5 to push the resin composition to fill the entire mold cavity 1, and then the resin composition is gradually cooled. When the temperature of the molded product drops to its demolding temperature, the mold can be opened and the obtained molded product can be taken out. Compared with conventional injection molding, the FAIM of the present invention can improve the surface quality of its products, reduce warpage deformation, lower the clamping force, reduce the product weight, and save costs.

[0029] In the method of the present invention, the molten semi-aromatic polyamide resin composition is obtained by heating to a temperature above its melting temperature (Tm) and below its decomposition temperature, and then the molten semi-aromatic polyamide resin composition is injected into the mold through the resin inlet 3 by an injection molding machine.

[0030] The amount of the semi-aromatic polyamide resin composition to be injected can be adjusted as desired, and for example, it may be 10 to 80%, preferably 20 to 70%, more preferably 30 to 60% of the capacity of the mold cavity 1. The mold temperature during steps (1) and (2) may be controlled within the range of 60 to 160°C, preferably 80 to 160°C, more preferably 120 to 160°C, and most preferably 140 to 160°C.

[0031] The start time of the fluid injection can be determined as needed. The wall thickness of the product can be controlled by selecting the start time of the fluid injection. When a larger wall thickness is required, there may be a large interval between the injection start time of the molten resin composition and the start time of the fluid injection. Typically, the fluid injection starts 0.5 to 15 seconds, preferably 0.5 to 10 seconds, after the injection start time of the molten resin composition.

[0032] The fluid used may be an inert gas or a liquid, such as air, nitrogen, steam or water. Its fluid pressure and temperature can be selected as required. For example, when the fluid is in the form of a gas, such as air, nitrogen or steam, its fluid pressure may be 0.1 to 5 MPa, preferably 1 to 4 MPa, and when the fluid is in the form of a liquid, such as water, its fluid pressure may be 1 to 50 MPa, preferably 5 to 30 MPa.

[0033] The fluid temperature may be within a wide range, such as -30°C to 100°C. The injection of the fluid can be carried out by an injection unit, such as a gas needle or a pump. The period of the fluid injection can be adjusted and may be 0.1 to 30 seconds, preferably 0.5 to 20 seconds, more preferably 5 to 20 seconds.

[0034] The injected fluid pushes the molten resin composition so as to fill the entire mold cavity 1 until the molten resin composition fits well on all the inner walls of the mold cavity 1.

[0035] Additionally, when there is too much molten resin composition in the mold cavity 1, the fluid can blow out the excess resin composition. In a preferred embodiment of the method, the overflow cavity 4 is at each end of the mold branch portion 6. Surprisingly, the presence of this overflow cavity 4 can improve the method reliability, and it has been found that products with a uniform wall thickness are produced. There are no special limitations on the shape and size of the overflow cavity 4, and the overflow cavity 4 may generally be cylindrical, and its diameter is usually smaller than the diameter of the branch portion.

[0036] In another embodiment of the present invention, the distance L2 from the plane D0 to the end of the longest branch portion (i.e., corresponding to the tip of the middle finger) is 10 times or less the distance L1 from the plane D0 to the end of the shortest branch portion (i.e., corresponding to the tip of the thumb), that is, L2 / L1 = 1:1 to 10:1, preferably L2 / L1 = 1:1 to 3:1.

[0037] Furthermore, there is no special limitation on the position of the resin inlet 3. The resin inlet 3 is normally located in the mold main pipe 2 and may be located in front of or behind the fluid inlet 5, preferably behind the fluid inlet.

[0038] After the fluid injection is completed, the fluid may be held in the mold cavity 1 for 1 to 30 seconds. Then, the fluid is discharged from the mold, and the molded product formed in the mold is cooled, for example, for 5 to 360 seconds. After cooling, the molded product is demolded from the mold.

[0039] After demolding, the obtained molded product may be subjected to post-treatment, such as trimming, surface cleaning, etc.

[0040] The semi-aromatic polyamide resin composition used in the present invention contains at least one semi-aromatic polyamide resin containing repeating units derived from an aromatic dicarboxylic acid, a diamine, and optionally other monomers, such as an amino acid and / or a lactam. The aromatic dicarboxylic acid may have 8 to 20 carbon atoms, more preferably 8 to 14 carbon atoms, and may be terephthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, or a mixture of isophthalic acid and at least one selected from terephthalic acid, naphthalenedicarboxylic acid, and diphenyldicarboxylic acid.

[0041] The semi-aromatic polyamide resin may contain repeating units derived from an aliphatic diamine. The aliphatic diamine in the present invention may be a linear or branched aliphatic diamine, preferably a linear aliphatic diamine. The aliphatic diamine preferably contains 6 to 36 carbon atoms, more preferably 6 to 22 carbon atoms or 36 carbon atoms, and most preferably 6 to 12 carbon atoms. Examples of the linear aliphatic diamine include 1,6-hexanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,11-undecanediamine, 1,12-dodecanediamine, 1,13-tridecanediamine, 1,14-tetradecanediamine, 1,16-hexadecanediamine, 1,18-octadecanediamine, 1,20-eicosanediamine and / or 1,22-docosanediamine, preferably 1,6-hexanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,11-undecanediamine and / or 1,12-dodecanediamine, more preferably 1,9-nonanediamine, 1,10-decanediamine, 1,11-undecanediamine and / or 1,12-dodecanediamine. Examples of the branched aliphatic diamine include 2-methyl-1,5-pentanediamine, 3-methyl-1,5-pentanediamine, 2-methyl-1,8-octanediamine, 5-methyl-1,9-nonanediamine, 2,4,4-trimethylhexamethylenediamine, 2,2,4-trimethylhexamethylenediamine and / or 2,4-dimethyloctanediamine, preferably 2-methyl-1,5-pentanediamine, 3-methyl-1,5-pentanediamine, 2-methyl-1,8-octanediamine, 2,4,4-trimethylhexamethylenediamine and / or 2,2,4-trimethylhexamethylenediamine.

[0042] Amino acids suitable in the present invention preferably contain 4 to 12 carbon atoms. Examples of the amino acid include 4-aminobutyric acid, 6-aminocaproic acid, 7-aminoheptanoic acid, 8-aminooctanoic acid, 10-aminodecanoic acid, 11-aminoundecanoic acid and / or 12-aminododecanoic acid.

[0043] Lactams suitable in the present invention preferably contain 4 to 12 carbon atoms, more preferably 6 to 12 carbon atoms. Examples of the lactam include 2-pyrrolidone (γ-butyrolactam), 2-piperidone (δ-valerolactam), ε-caprolactam, capryllactam, decanolactam, undecanolactam, enanthlactam and / or lauryllactam, preferably ε-caprolactam and / or undecanolactam.

[0044] In a preferred embodiment, the semi-aromatic polyamide resin contains repeating units derived from a dicarboxylic acid containing at least one of the above aromatic dicarboxylic acids and a diamine containing at least one of the above aliphatic diamines. Preferably, the aliphatic diamine has 8 to 14 carbon atoms.

[0045] Preferably, the semi-aromatic polyamide resin is a polyphthalamide (PPA) resin, such as PA4T, 5T, 6T, PA8T, PA9T, 10T or 12T, preferably PA9T. Surprisingly, when PA9T is used, the resulting molded article has good chemical resistance, low water absorption, good swelling resistance, and good dimensional stability, which have been found to be ideal as glove molding dies.

[0046] The semi-aromatic polyamide resin in the present invention may be a polyamide copolymer or a blend of two or more polyamides and copolyamides, such as PA6T / 6I, PA6T / 66, PA6T / 8T, PA6T / 10T, PA6T / 10I, PA10T / 10I, PA6T / 9T, PA6T / 12T, PA4T / 6T / DT, PA4T / 10T / DT, PA4T / 4I / 6T / 6I / DT / DI, PA6T / 12T / 6I / 12I, PA6T / 10T / 6I, PA4T / 6T / 4I / 6I, PA5T / 6T / 5I / 6I, PA5T / 4T / 5I / 4I, PA4T / 10T / 5I / 10I, PA4T / 6T / DT, PA4T / 10T / DT or PA4T / 4I / 6T / 6I / DT / DI, preferably PA6T / 6I, PA6T / 10T, PA6T / 12T, PA6T / 10T / 6I, PA6T / DT and / or PA6T / DT / 6I / DI. Here, D is 2-methyl-1,5-pentanediamine or 3-methyl-1,5-pentanediamine, or a mixture thereof.

[0047] When no filler is used, the preferred amount of the semi-aromatic polyamide resin is 50 to 100% by weight, preferably 90 to 100% by weight, based on the total amount of the semi-aromatic polyamide resin composition; and when a filler is used, it is 50 to 95% by weight, preferably 60 to 90% by weight, more preferably 70 to 85% by weight.

[0048] The semi-aromatic polyamide resin composition may contain 0 to 50% by weight of a filler commonly used in the art. There is no limitation on the form of the filler, such as fiber, whisker, flake, or particle.

[0049] The fibers may be, for example, inorganic fibers such as glass fibers, boron fibers, carbon fibers, silica fibers, ceramic fibers, wollastonite fibers, metal fibers, potassium titanate fibers, aluminum borate fibers, and basalt fibers; reinforcing organic fibers such as aramid fibers, polyester fibers, nylon fibers, and polyethylene fibers; and natural fibers such as wood fibers, linen fibers, hemp fibers, and sisal fibers. Glass fibers, carbon fibers, and aramid fibers are preferred. The fibers may be chopped fibers having a length of, for example, 2 to 500 mm, preferably 3 to 200 mm, and a diameter of 5 to 40 μm, preferably 10 to 25 μm. The fibrous filler in the polyamide composition preferably has an average length of 2 to 500 μm, preferably 200 to 300 μm, more preferably 220 to 240 μm. The fibers may be present in an amount of 5 to 50% by weight, preferably 10 to 45% by weight, more preferably 15 to 35% by weight, based on the total weight of the composition. The fibers can be introduced by directly blending the chopped fibers with the semi-aromatic polyamide resin and then extruding; or by using long fiber strands and drawing them together with the semi-aromatic polyamide resin and then chopping. The fibers may be surface-treated fibers, for example, treated with a silane coupling agent.

[0050] Optionally, the filler is used in the form of particles. The particulate filler may have a variety of particle sizes ranging from dust-like particles to coarse particles. The particles used may include organic particles or inorganic particles. Examples of materials that can be used are inorganic particles such as kaolin, chalk, wollastonite, talc, calcium carbonate, silicate, titanium dioxide, zinc oxide, graphite, mica, vermiculite, montmorillonite, and glass particles (e.g., glass beads). The particles may be surface-treated fillers. The particle content may be 5 to 50% by weight, preferably 10 to 45% by weight, more preferably 15 to 35% by weight, based on the total weight of the composition.

[0051] In addition to the filler, the semi-aromatic polyamide resin composition may optionally contain other additives commonly used in the art, such as lubricants, heat stabilizers, flame retardants, light stabilizers (ultraviolet stabilizers, ultraviolet absorbers or ultraviolet blockers), nucleating agents, pigments and dyes, antistatic agents, fluorescent brighteners, surface modifiers, fluidity improvers, etc.

[0052] The additives may be used in a total amount of 0 to 10% by weight, preferably 0 to 5% by weight, more preferably 0 to 2% by weight, based on the total weight of the composition.

[0053] The lubricant includes any one or at least a combination of two or more of stearate, titanate, stearic acid, erucamide, oleamide or silicone. Extremely particularly preferred lubricants are calcium stearate, calcium montanate or aluminum stearate.

[0054] The heat stabilizer is preferably selected from copper compounds, aromatic secondary amines, sterically hindered phenols, phosphites, phosphinites and mixtures thereof.

[0055] Examples of suitable copper compounds are salts of monovalent or divalent copper with inorganic or organic acids or with monofunctional or bifunctional phenols, complexes of monovalent or divalent copper oxide with ammonia, with amines, with amides, with lactams, with cyanides or with phosphines, preferably Cu(I) or Cu(II) salts of hydrohalic acids or hydrocyanic acid, or copper salts of aliphatic carboxylic acids. The monovalent copper compounds are particularly preferably CuCl, CuBr, CuI, CuCN and Cu2O, and the divalent copper compounds are particularly preferably CuCl2, CuSO4, CuO, copper(II) acetate or copper(II) stearate.

[0056] Examples of aromatic secondary amine stabilizers are adducts of phenylenediamine with acetone (Naugard® A), adducts of phenylenediamine with linolenic acid, or 4,4'-bis(α,α-dimethylbenzyl)diphenylamine (Naugard® 445), N,N'-dinaphthyl-p-phenylenediamine, N-phenyl-N'-cyclohexyl-p-phenylenediamine, or mixtures of two or more thereof.

[0057] Preferred examples of sterically hindered phenol stabilizers are N,N'-hexamethylenebis-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide, bis-(3,3-bis-(4'-hydroxy-3'-tert-butylphenyl)butyrate), 2,1'-thioethylbis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 4,4'-butenylbis(3-methyl-6-tert-butylphenol), triethylene glycol=3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate, and mixtures of two or more of these stabilizers.

[0058] Examples of phosphites and phosphonites include triphenyl phosphite, diphenyl alkyl phosphite, phenyl dialkyl phosphite, tris(nonylphenyl) phosphite, trilauryl phosphite, tris-tridecyl phosphite, distearyl pentaerythritol diphosphite, tris(2,4-di-tert-butylphenyl) phosphite, diisodecyl pentaerythritol diphosphite, bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite, bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite, diisodecyloxy pentaerythritol diphosphite, bis(2,4-di-tert-butyl-6-methylphenyl) pentaerythritol diphosphite, bis(2,4,6-tri(tert-butylphenyl)) pentaerythritol diphosphite, tristearoyl sorbitol triphosphite, tetrakis(2,4-di-tert-butylphenyl)-4,4'-biphenylene diphosphonite, 6-isooctyloxy-2,4,8,10-tetra-tert-butyl-12H-dibenzo[d,g]-1,3,2-dioxaphosphacyclooctadiene, 6-fluoro-2,4,8,10-tetra-tert-butyl-12-methyl dibenzo[d,g]-1,3,2-dioxaphosphacyclooctadiene, bis(2,4-di-tert-butyl-6-methylphenyl) methyl phosphite, bis(2,4-di-tert-butyl-6-methylphenyl) ethyl phosphate and tris[2-tert-butyl-4-thio(2'-methyl-4'-hydroxy-5'-tert-butyl)-phenyl-5-methyl] phenyl phosphite.

[0059] Examples of flame retardants include halogen-containing and halogen-free flame retardants and their synergists. Preferred halogen-free flame retardants include red phosphorus, phosphinates or bisphosphinates and / or nitrogen-containing flame retardants such as melamine, melamine cyanurate, melamine sulfate, melamine borate, melamine oxalate, melamine phosphate, trihydroxyethyl isocyanurate.

[0060] Examples of light stabilizers are resorcinols, salicylates, benzotriazoles and benzophenones, as well as sterically hindered P-containing compounds, sterically hindered amines and carbodiimides.

[0061] The nucleating agent used may be sodium phenylphosphonite, alumina, silica, or talc, preferably talc.

[0062] The pigments used may be inorganic pigments such as titanium dioxide, ultramarine, iron oxide, ZnO and boehmite, AlO(OH), etc.; organic pigments such as phthalocyanine, quinacridone or perylene, etc. The dyes are all dyes that can be used for transparent, semi-transparent or opaque coloring, especially those suitable for coloring polyamides. Among them, those suitable for transparent and semi-transparent coloring are preferred. Such dyes are known to those skilled in the art.

[0063] The production of the semi-aromatic polyamide resin composition is achieved by a method known per se. This includes mixing the components in appropriate weight ratios. The components are preferably mixed at an elevated temperature by coalescence, mixing, kneading, extrusion or rolling. The mixing temperature is preferably 300 - 350 °C, especially 310 - 340 °C, especially 320 - 340 °C. Suitable methods are known to those skilled in the art.

[0064] In a preferred embodiment, the semi-aromatic polyamide resin composition is as follows: i) 50 - 95% by weight, preferably 60 - 90% by weight, more preferably 70 - 85% by weight of a semi-aromatic polyamide resin, preferably PPA; ii) 5 - 50% by weight, preferably 10 - 45% by weight, more preferably 15 - 35% by weight of a filler, and iii) Optionally, additives, preferably heat stabilizers are included.

[0065] In a more preferred embodiment, the semi-aromatic polyamide resin composition is as follows: i) 50 to 95% by weight, preferably 60 to 90% by weight, more preferably 70 to 85% by weight of PA9T; ii) 5 to 50% by weight, preferably 10 to 45% by weight, more preferably 15 to 35% by weight of glass fiber, and iii) Optionally, additives, preferably heat stabilizers are included.

[0066] The molded article of the present invention In another aspect, the present invention relates to a hollow molded article that is integral and has a main pipe at one end and a plurality of branch portions at the other end, wherein the branch portions are connected to the main pipe, and here, the molded article is made of a semi-aromatic polyamide resin composition.

[0067] The dimensions of the main pipe and the branch portions are as described above for the method of manufacturing the molded article. Moreover, there is an inflection point in the main pipe of the mold.

[0068] The hollow molded article may have 2 to 100, preferably 2 to 50, more preferably 2 to 20, most preferably 3 to 6 branch portions, for example, 2 branch portions, 3 branch portions, 4 branch portions, 5 branch portions, 6 branch portions. The branch portions may have the same or different lengths, preferably different lengths.

[0069] The wall thickness of the molded article can be adjusted as necessary and may be, for example, 2 to 8 mm, preferably 2 to 5 mm, more preferably 3 to 4 mm.

[0070] The main pipe of the hollow molded article has an opening at the end away from the branch portions. The major axis of the opening may be the same as or slightly smaller than the end of the main pipe.

[0071] The main pipe may have a major axis that is constant in the direction of its length or may have a major axis that varies in the direction of its length, for example, having a plurality of different major axes from the opening of the main pipe to the position where the branch portions are located. Preferably, the main pipe has a major axis that varies in the direction of its length.

[0072] The molded product may have an inflection point (i) at which the variation trend of the major axis changes. The major axis is the longer axis along the length direction of each cross-section of the main pipe, or when the major axes have the same length, it may have a joining point (ii) between the main pipe and the nearest branch portion.

[0073] When the major axes of the cross-sections of the main pipe have different lengths, the inflection point means the point at which the variation trend of the major axis of each cross-section of the main pipe along its length direction changes. For example, when viewed from the opening, in front of the inflection point, the major axis of the main pipe changes from large to small, while behind this point, the major axis of the main pipe changes from small to large. The "front" and "rear" are used only to indicate their relative positions and are not used to define the detailed positions. The major axis corresponds to the diameter when the cross-section of the main pipe is circular.

[0074] When the major axes of the cross-sections of the main pipe have the same length, the inflection point means the joining point between the main pipe and the nearest branch portion.

[0075] Here, the inflection point refers to the portion in the molded product corresponding to the portion of the mold.

[0076] In one embodiment of the present invention, the molded product is a glove molding die. In this case, the hollow molded product has the shape of a glove. In particular, the molded product has the shape of a glove including a sleeve-shaped region, a palm-shaped region, and a finger-shaped region. The mold main pipe 2 is used to form the sleeve-shaped region and the palm-shaped region of the glove, while the mold branch portion 6 is used to form the finger-shaped region, and the number of branch portions is 5. The glove molding die usually has branch portions. The mold main pipe 2 may have a length and dimensional size corresponding to the sleeve-shaped region and the palm-shaped region of the glove to be manufactured; the plurality of branch portions may have different lengths and diameters corresponding to the finger-shaped region.

[0077] In a more preferred embodiment, for the glove molding die, the distance L2 from the plane D0 to the end of the longest branch (i.e., corresponding to the tip of the middle finger) is at most 10 times the distance L1 from the plane D0 to the end of the shortest branch (i.e., corresponding to the tip of the thumb), that is, L2 / L1 = 1:1 to 10:1, preferably L2 / L1 = 1:1 to 3:1. The plane D0 is a plane where its inflection joint is located and is perpendicular to the length direction of the main die tube 2.

[0078] In a more preferred embodiment, for the glove molding die, the thickness of the glove molding die is 2 to 5 mm, preferably 3 to 4 mm.

[0079] The semi-aromatic polyamide resin composition used is the above-mentioned one for the method of manufacturing the above-mentioned molded article.

[0080] Use of the molded article according to the present invention In another aspect, the present invention relates to the use of the molded article of the present invention or the molded article obtainable by the method of the present invention as an immersion molding die, preferably a glove molding die.

[0081] The dipping mold is a structural element that can take the shape of the object and enable the formation of a dipping mold corresponding to the shape of the object. The dipping mold may be manufactured by a so-called dipping method. In such a method, the dipping mold is dipped or immersed in a polymer emulsion, preferably a rubber latex or a vinyl polymer emulsion, and the polymer particles in the emulsion, more specifically the rubber particles in the latex, coalesce and form an aggregated polymer film on the dipping mold. The film takes the shape of the dipping mold. In its simplest form, dipping is a process in which a thin polymer (usually rubber) product is first immersed in a preferably formulated polymer emulsion or rubber latex, and then the mold is slowly removed from the emulsion or latex in such a way as to leave a uniform deposit on the mold. The thickness of the deposit can be increased, if desired, by repeating the dipping and coalescence steps. The formation of the product is completed by leaching, drying and, if necessary, subjecting it to appropriate treatment, the most obvious of which is vulcanization of the rubber. The product may be subjected to appropriate post-treatment. In many cases, it is practical to form a rounded bead at the open end of the molded article. The purpose of the bead is mainly to reinforce its thin film against the initiation of tearing from the edge of the open end. It also prevents extremely thin molded articles from adopting various twisted configurations. The product is usually removed from the mold before use.

[0082] When the molded article of the present invention is used as a dipping mold, preferably a glove mold, it has a surface quality comparable to that of conventional metal, ceramic or glass molds, but is lightweight and can withstand the glove manufacturing process including high temperature, mechanical operation and chemical exposure. Therefore, the molded article of the present invention has a long service life, usually exceeding two years, when used as a dipping mold, which is much longer than that of conventional ceramic molds (usually 0.5 to 1 year).

Examples

[0083] The present invention will be further described by the following examples, but the present invention is not limited to those examples.

[0084] General procedure This semi-aromatic polyamide resin composition is Ultramid Advanced N3HG6 LS BK from BASF, which is manufactured from PA9T, 30% glass fiber, and a heat stabilizer.

[0085] The pelletized PA9T composition was injection molded at 330 °C in an airmould (registered trademark) next fluid assist injection molding machine. The mold was used to mold a glove molding mold, and the mold temperature was 140 °C. The semi-aromatic polyamide resin composition melt was injected for 3.5 seconds. Nitrogen injection was started 3.0 seconds after the start of injection of the resin composition. The nitrogen temperature was 23 °C, and its pressure was 1.8 MPa. The period of nitrogen injection was 15 seconds. After the nitrogen injection was completed, the pressure in the mold cavity was held constant for 10 seconds, and then the nitrogen was discharged. After the mold was cooled for 100 seconds, the mold was demolded, and the molded product was taken out. In the above procedure, the resin inlet is located behind the fluid inlet and 3 cm away from the fluid inlet.

[0086] The mold used is shown in Figure 2, where its parameters are shown below: L1: 135 mm L2: 213 mm L3: 202 mm L4: 207 mm L5: 182 mm d1: 22 mm d2: 20 mm d3: 20 mm d4: 20 mm d5: 20 mm.

[0087] The molded product of Example 3 is shown in Figure 3, where its parameters are shown below: L1: 130 mm L2: 208 mm L3: 197 mm L4: 202 mm L5: 177 mm d1: 17.8 mm d2: 14.6 mm, d3: 16.5 mm d4: 15.5 mm, d5: 13.0 mm d0: 58.5 mm, D1: 114 mm The thickness of the molded product is within the range of 2 to 4 mm.

[0088] Comparative Example 1 This molded product was manufactured according to the above general procedure, where the fluid inlet is located 1 / 5 of the distance L2 from the plane D0, that is, LF = 42 mm. L1 of the first branch (corresponding to the thumb) is 60 mm, and L5 of the fifth branch (corresponding to the little finger) is 80 mm, which is only about half of L1 and L5 of the molded product manufactured in Example 3. L3 of the second branch (corresponding to the index finger) is 147 mm, L4 of the fourth branch (corresponding to the ring finger) is 181 mm. L2 (corresponding to the middle finger) is 206 mm.

[0089] Comparative Example 2 Repeat Comparative Example 1, except that the fluid inlet is located 1 / 3 of the distance L2 from the plane D0, that is, LF = 71 mm. L1 of the first branch (corresponding to the thumb) is 97 mm, and L5 of the fifth branch (corresponding to the little finger) is 131 mm, which are only about 3 / 4 of L1 and L5 of the molded product manufactured in Example 3. L3 of the second branch (corresponding to the index finger) is 177 mm, L4 of the fourth branch (corresponding to the ring finger) is 151 mm. L2 (corresponding to the middle finger) is 207 mm.

[0090] Example 3 Repeat Comparative Example 1, except that the fluid inlet is located 1 / 2 of the distance L2 from the plane D0, that is, LF = 105 mm.

[0091] Result Evaluation The surfaces of the molded products obtained from Comparative Examples 1 and 2 and Example 3 were evaluated.

[0092] The surfaces of the molded articles obtained from Comparative Examples 1 and 2 and Example 3 were smooth, free of defects such as cracks, bubbles and holes, and not rich in glass fibers on said surfaces. Each of the branched portions of the molded article obtained from Example 3 was completely filled and its wall thickness was uniform. However, the molded articles obtained from Comparative Examples 1 and 2 were not completely filled and their wall thickness was not uniform.

[0093] The glove mold of Example 3 was found to be used in a factory manufacturing nitrile rubber gloves and to have a service life exceeding two years.

[0094] The molded articles produced from Example 3 have an alkali corrosion rate in a 10 wt% NaOH solution of 0.012% and an acid corrosion rate in a 10 wt% HNO3 solution of 0.018%. They were tested by immersing the molded articles in an acid or alkali solution at room temperature and checking the weight change after 48 hours.

Explanation of Reference Signs

[0095] 1 Mold cavity, 2 Mold main pipe, 3 Resin inlet, 4 Overflow cavity, 5 Fluid inlet, 6 Mold branch portion, L1 Distance from plane D0 to the end of the shortest branch portion, L2 Distance from plane D0 to the end of the longest mold branch portion, LF Distance from the fluid inlet to plane D0

Claims

1. A method for manufacturing a hollow molded article, comprising manufacturing the hollow molded article by fluid-assisted injection molding, the method including the following steps: Step (1): Injecting a molten resin composition into a mold having a mold cavity (1) and at least one overflow cavity (4), the mold cavity (1) including a mold main pipe (2) and a plurality of mold branch portions (6) connected to the mold main pipe (2), the resin composition being a semi-aromatic polyamide resin composition, the mold main pipe (2) having an inflection point (i) at which the variation tendency of the major axis changes, the major axis being the longer axis of each cross-section of the mold main pipe (2) along its length direction, or having a joint point (ii) of the mold main pipe (2) and the nearest mold branch portion (6) when the major axes have the same length, Step (2): Injecting a fluid into the molten resin composition through a fluid inlet (5) to obtain the molded article, the fluid inlet (5) being located inside the mold main pipe (2), and the distance LF from the fluid inlet (5) to a plane D0 being at least 1 / 2 of the distance L2 from the plane D0 to the end of the longest mold branch portion (6), the plane D0 being a plane in which the inflection joint is located and perpendicular to the length direction of the mold main pipe (2), Step (3): Demolding the molded article. Here, the molded article is integral and has a main pipe at one end and a plurality of branch portions at the other end, the branch portions being connected to the main pipe, and here, the method, wherein the molded article is made of a semi-aromatic polyamide resin composition.

2. The method for manufacturing a hollow molded article according to Claim 1, wherein the distance LF is 5 times or less, preferably 3 times or less, of L2.

3. The method for manufacturing a hollow molded article according to Claim 1 or 2, wherein the fluid injection starts 0.5 to 15 seconds, preferably 0.5 to 10 seconds, after the start time of the injection of the molten resin composition.

4. The method for manufacturing a hollow molded article according to any one of Claims 1 to 3, wherein the period of the fluid injection is 0.1 to 30 seconds, preferably 0.5 to 20 seconds, more preferably 5 to 20 seconds.

5. When the fluid is in the form of a gas, the fluid pressure is 0.1 to 5 MPa, preferably 1 to 4 MPa, and when the fluid is in the form of a liquid, the fluid pressure is 1 to 50 MPa, preferably 5 to 30 MPa, and the fluid temperature is -30°C to 100°C. A method for manufacturing the hollow molded article according to any one of claims 1 to 4.

6. A method for manufacturing the hollow molded article according to any one of claims 1 to 5, wherein one overflow cavity (4) is provided at each end of the mold branch portion (6) of the mold.

7. The ratio of the distance L2 from the plane D0 to the end of the longest branch portion to the distance L1 from the plane D0 to the end of the shortest branch portion is in the range of 1:1 to 10:1, preferably 1:1 to 3:

1. A method for manufacturing the hollow molded article according to any one of claims 1 to 6.

8. A method for manufacturing the hollow molded article according to any one of claims 1 to 7, wherein the mold temperature during steps (1) and (2) is controlled within the range of 60 to 160°C.

9. The semi-aromatic polyamide resin composition contains at least one semi-aromatic polyamide resin containing repeating units derived from an aromatic dicarboxylic acid, a diamine, and optionally other monomers, such as amino acids and / or lactams. A method for manufacturing the hollow molded article according to any one of claims 1 to 8.

10. The aromatic dicarboxylic acid has 8 to 20 carbon atoms, and is preferably selected from the group consisting of terephthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, or a mixture of at least one selected from terephthalic acid, naphthalenedicarboxylic acid, and diphenyldicarboxylic acid and isophthalic acid. A method for manufacturing the hollow molded article according to any one of claims 1 to 9.

11. Based on the total amount of the semi-aromatic polyamide resin composition, when no filler is used, the semi-aromatic polyamide resin is present in an amount of 50 to 100% by weight, and when a filler is used, the semi-aromatic polyamide resin is present in an amount of 50 to 95% by weight. A method for manufacturing the hollow molded article according to any one of claims 1 to 10.

12. A hollow molded article, which is integral and has a main pipe at one end and a plurality of branch parts at the other end, the branch parts being connected to the main pipe, and the molded article being made of a semi-aromatic polyamide resin composition, the hollow molded article.

13. The hollow molded article according to claim 12, wherein the hollow molded article is manufactured by the method according to any one of claims 1 to 11.

14. The hollow molded article according to claim 12 or 13, wherein the molded article has 2 to 100, preferably 2 to 50, more preferably 2 to 20, and most preferably 3 to 6 branch parts.

15. The hollow molded article according to any one of claims 12 to 14, wherein the wall thickness of the molded article is 2 to 8 mm, preferably 2 to 5 mm, more preferably 3 to 4 mm.

16. The hollow molded article according to any one of claims 12 to 15, wherein the hollow molded article is an immersion molding die.

17. The hollow molded article according to claim 16, wherein the immersion molding die is a glove molding die.

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