Method for producing a hollow molded part and hollow molded part obtained thereby

Abstract

The invention relates to a method for producing a hollow moulded part, comprising producing the hollow moulded part by fluid-assisted injection moulding, comprising the following steps: step (1): injecting a molten resin composition into a mould having a mould cavity (1) and at least one overflow cavity (4), wherein the mold cavity (1) comprises a mold main duct (2) and a plurality of mold branches (6), the mold main duct (2) having an inflection point (i) at which the trend of the change of the long axis, which is the longer axis of each section of the mold main duct (2) in the length direction thereof, changes, or having (ii) the junction of the mold main duct (2) and the closest mold branch (6), if the long axes have the same length, step (2): injecting a fluid into the molten resin composition via a fluid inlet (5) inside the mold main duct (2) and a distance LF from the fluid inlet (5) to a plane D0 is not less than 1 / 2 of a distance L2 from the plane D0 to an end of a longest mold branch (6) to obtain the molded part, the plane D0 is a plane in which the inflection joint is located and perpendicular to the length direction of the mold main duct (2), step (3): demolding the molded part, in which the molded part is integral and has a main duct at one end and a plurality of branches at the other end, the branches being connected to the main duct, wherein the molded part is made of a semi-aromatic polyamide resin composition. The invention further relates to a hollow molded part obtained by this method.

Description

Technical Field

[0001] The invention relates to a method for producing a hollow molded part, and to a hollow molded part obtained by the method. Background Art

[0002] A dipping former is a part used to shape a dipped product (such as a rubber glove) by dip molding. In dip molding, the dip former is dipped into a polymer emulsion, the polymer particles in the emulsion aggregate on the dip former and form a polymer film, and then the former is taken out of the emulsion, with a uniform deposit left on the former. If necessary, the thickness of the deposit can be increased by repeated dipping. After the dipped product is shaped, it can be leached, vulcanized and dried, and then demoulded.

[0003] Traditionally, metals (especially aluminum) and ceramics or glass are used to manufacture such molders. However, metals have the disadvantages of being easily oxidized, not resistant to corrosive components (such as acids), having poor wear resistance and a short service life. On the other hand, ceramics and glass are brittle and cannot withstand thermal and mechanical shocks, and can be dangerous for operators when they break. In addition, the heavy weight of metal, ceramic or glass molders means that high energy consumption is required in the manufacture of the molded parts.

[0004] The dip former needs to have low weight and long service life to provide cost effectiveness.

[0005] There have been several attempts by glove former companies and plastic suppliers to address the above issues and provide methods to provide plastic solutions that are comparable in appearance to metal, ceramic or glass but are lightweight.

[0006] For example, CN 107053564A discloses a method for manufacturing a plastic glove former, which includes injection molding the upper shell and the lower shell of the glove former separately, and then welding them into a complete glove former. In addition, CN206066990U discloses a glove dip former, which is made of glass fiber reinforced polyamide 4T and is formed by welding different sections or halves together. Both of these formers are not one-piece, but need to be welded to form a whole. This increases the cost and is prone to damage during use.

[0007] WO 2020260456A1 describes a glove former for latex dipping, which is one-piece on the surface and is molded by an injection or blow molding process. In WO 2020260456A1, the former includes a core-shell structure, and it is necessary to manufacture the two parts via a separate molding process. The glove former is produced by a process comprising the following steps: injection molding or blow molding a first material into a first cavity to make a core; transferring the molded core to a second cavity; and injection molding a second material into the second cavity to overmold the molded core. The complex design creates challenges in the molding process, such as difficulty in retrieving the core parts. However, no solution is mentioned.

[0008] CN 108099067A discloses a method for integrally molding a plastic glove former. The method includes molding the glove former in an injection molding machine connected to a nitrogen production device. However, it does not describe the technical design related to the fluid inlet and overflow cavity. In addition, only fluoroplastics are used to mold the glove former.

[0009] Alternative solutions with plastics were attempted to replace the ceramics used for formers from the above prior art, which posed some technical challenges, such as

[0010] a). The complex geometry of the mold (including undercuts) increases the difficulty of demoulding when using injection molding;

[0011] b) The two-step manufacturing method increases the total manufacturing cost and deteriorates reproducibility, such as unstable welding performance;

[0012] c) One-step manufacturing methods (such as liquid-assisted molding) cannot achieve good surface and uniform part thickness;

[0013] d). Standard plastics do not meet the need for long term chemical resistance during cleaning and washing phases. Summary of the invention

[0014] The object of the present invention is to overcome at least one of the above-mentioned problems of the prior art and to provide a method for producing a hollow molded part and a one-piece hollow molded part which has a smooth and uniform surface appearance but is lightweight compared to metal or ceramic molded parts and can withstand long-term tests under high temperatures, mechanical operations and chemical exposure.

[0015] This object has been achieved by a method for producing a hollow molded part, which method comprises producing the hollow molded part by fluid-assisted injection molding.

[0016] The object has also been achieved by a hollow molded part which is one-piece and has a main duct at one end and a plurality of branches at the other end, wherein the molded part is made of a semiaromatic polyamide resin composition.

[0017] The molded part is one-piece. In the context of the present invention, the term "one-piece" means that the molded part itself is formed in one piece, without joining (such as welding, fusing or assembling) different parts during its production.

[0018] The term "distance" is the perpendicular dimension from a point to a plane. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of the method of the present invention is shown;

[0020] Figure 2 An embodiment of a molded part of the present invention is shown; and

[0021] Figure 3 The molded part of Example 3 is shown with various dimensions. DETAILED DESCRIPTION

[0022] Method for producing a molded part

[0023] In one aspect, the present invention relates to a method for producing a hollow molded part, the method comprising producing the molded part by fluid assisted injection molding (FAIM), the method comprising the following steps:

[0024] (1) injecting a molten resin composition into a mold having a mold cavity 1 and at least one overflow cavity 4, wherein the mold cavity 1 includes a mold main duct 2 and a plurality of mold branches 6 connected to the mold main duct 2, the resin composition is a semi-aromatic polyamide resin composition, the mold main duct 2 has an inflection point (i) at which the trend of the major axis, which is the longer axis of each cross section of the mold main duct 2 along its length direction, changes, or has (ii) a junction point between the mold main duct 2 and the nearest mold branch 6, if these major axes have the same length,

[0025] (2) injecting a fluid into a molten resin composition through a fluid inlet 5 to obtain a molded part, the fluid inlet 5 being located inside the mold main duct 2, and a distance LF from the fluid inlet 5 to a plane D0 being not less than 1 / 2 of a distance L2 from the plane D0 to the end of the longest mold branch 6, the plane D0 being a plane in which the inflection joint is located and being perpendicular to the length direction of the mold main duct 2,

[0026] (3) demoulding the molded part,

[0027] The molded part is one-piece and has a main conduit at one end and a plurality of branches at the other end, the branches being connected to the main conduit, wherein the molded part is made of a semi-aromatic polyamide resin composition.

[0028] The mold main conduit 2 may have a constant long axis in the length direction, or a variable long axis in the length direction, for example, a plurality of different long axes from the opening of the mold main conduit 2 to the location of the mold branch. Preferably, the mold main conduit 2 has a variable long axis in the length direction.

[0029] If the major axis of the cross section of the mold main conduit 2 has different lengths, the inflection point means the point where the change trend of the major axis of each cross section of the mold main conduit 2 along its length direction changes. For example, as viewed from the opening, before the inflection point, the major axis of the mold main conduit 2 changes from large to small, and after this point, the major axis of the mold main conduit 2 changes from small to large. "Before" and "after" are only used to present relative positions, and are not used to define specific positions. If the cross section of the mold main conduit 2 is circular, the major axis corresponds to the diameter.

[0030] If the major axes of the cross-section of the mold main duct 2 have the same length, the inflection point means the junction of the mold main duct 2 and the nearest mold branch 6 .

[0031] Plane D0 is a preset plane in which the inflection point is located and is perpendicular to the length direction of the mold main conduit 2. In the case where there is more than one inflection point in the length direction of the mold main conduit 2, all planes that meet the requirements of plane D0 may be plane D0. The plane including the inflection point farthest from the mold branch 6 is the preferred plane D0.

[0032] In conventional FAIM, it is difficult to completely fill each mold branch with resin composition and make the wall thickness uniform. However, in the present invention, it is unexpectedly found that when a suitable position of the fluid inlet 5 is selected, each mold branch can be filled with resin composition and a molded part with uniform wall thickness and length can be obtained.

[0033] Specifically, the fluid inlet 5 is located inside the mold main duct 2 (the mold main duct 2 corresponds to the main duct of the molded part), and the distance LF from the position of the fluid inlet 5 to the plane D0 is not less than 1 / 2 of the distance L2 from the plane D0 to the end of the longest mold branch 6 (when the molded part of the present invention is a glove former, it corresponds to the tip of the middle finger), that is, LF≥1 / 2L2.

[0034] In a preferred embodiment, the distance LF is not higher than 5 times of L2, preferably not higher than 3 times of L2.

[0035] The molded part can have 2 to 100, preferably 2-50, more preferably 2-20, most preferably 3-6 branches. These branches can have the same or different lengths, preferably different lengths.

[0036] The wall thickness of the molded part can be adjusted as desired and may be, for example, 2-8 mm, preferably 2-5 mm, more preferably 3-4 mm.

[0037] The main conduit of the hollow molded part has an opening at the end remote from the junction with the branch. The diameter of the opening can be the same as or slightly smaller than the end of the main conduit.

[0038] In the FAIM of the present invention, a mold having a mold cavity 1 having a shape corresponding to the hollow molded part to be produced is used. In particular, the mold cavity 1 comprises a mold main duct 2 corresponding to the main duct of the molded part and mold branches 6 corresponding to the branches of the molded part.

[0039] In the FAIM process, a molten semi-aromatic polyamide resin composition is injected into a mold cavity 1 via a resin inlet 3, and then a fluid is injected into the resin composition via a 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 part drops to the demolding temperature, the mold can be opened and the obtained molded part can be taken out. Compared with conventional injection molding, the FAIM of the present invention can improve product surface quality, reduce warpage, reduce clamping force, reduce product weight and save costs.

[0040] In the method of the present invention, a molten semiaromatic polyamide resin composition is obtained by heating to a temperature higher than its melting temperature (Tm) and lower than its decomposition temperature, and then the molten semiaromatic polyamide resin composition is injected into a mold through a resin inlet 3 by an injection molding machine.

[0041] The amount of the injected semiaromatic polyamide resin composition can be adjusted as needed, and for example, can be 10%-80%, preferably 20%-70%, more preferably 30%-60% of the capacity of the mold cavity 1. The mold temperature during steps (1) and (2) can be controlled within the range of 60°C-160°C, preferably 80°C-160°C, more preferably 120°C-160°C, most preferably 140°C-160°C.

[0042] The start time of fluid injection can be determined as needed. The wall thickness of the product can be controlled by selecting the start time of 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 fluid injection. Typically, the fluid injection starts 0.5-15 seconds, preferably 0.5-10s after the injection start time of the molten resin composition.

[0043] The fluid used can be an inert gas or a liquid, such as air, nitrogen, steam or water. Fluid pressure and temperature can be selected as required. For example, if the fluid is in the form of a gas (for example, air, nitrogen or steam), the fluid pressure can be 0.1-5MPa, preferably 1-4MPa, and if the fluid is in the form of a liquid (for example, water), the fluid pressure can be 1-50MPa, preferably 5-30MPa.

[0044] The fluid temperature can be in a wide range, such as -30°C to 100°C. The injection of the fluid can be carried out by means of an injection unit (such as a gas needle or a pump). The duration of the fluid injection can be adjusted and can be 0.1-30 seconds, preferably 0.5-20 seconds, more preferably 5-20 seconds.

[0045] The injected fluid pushes the molten resin composition to fill the entire mold cavity 1 until the molten resin composition adheres to all inner walls of the mold cavity 1 .

[0046] In addition, when there is too much molten resin composition in the mold cavity 1, the fluid can cause the excess resin composition to overflow. In a preferred embodiment of the present method, there is an overflow cavity 4 at each end of the mold branch 6. Surprisingly, it was found that the presence of the overflow cavity 4 can improve process reliability, thereby obtaining a product with uniform wall thickness. There is no particular restriction on the shape and size of the overflow cavity 4, and it can generally be cylindrical, and its diameter is generally smaller than the diameter of the branch.

[0047] In another embodiment of the present invention, the distance L2 from plane D0 to the end of the longest branch (i.e., corresponding to the tip of the middle finger) is less than or equal to 10 times the distance L1 from plane D0 to the end of the shortest branch (i.e., corresponding to the tip of the thumb), that is, L2 / L1=1:1~10:1, preferably, L2 / L1=1:1~3:1.

[0048] Furthermore, there is no particular limitation on the position of the resin inlet 3 , which is usually located in the mold main conduit 2 and can be located before or after the fluid inlet 5 , preferably after the fluid inlet.

[0049] After the fluid injection is completed, the fluid can be kept in the mold cavity 1 for 1-30 seconds. Then, the fluid is discharged from the mold, and the molded part formed in the mold is allowed to cool, for example, for 5-360 seconds. After cooling, the molded part is demoulded from the mold.

[0050] After demoulding, the obtained molded part can be subjected to post-treatment, such as trimming, surface cleaning and the like.

[0051] The semi-aromatic polyamide resin composition used in the present invention comprises at least one semi-aromatic polyamide resin comprising repeating units derived from aromatic dicarboxylic acids, diamines, and optionally other monomers such as amino acids and / or lactams. The aromatic dicarboxylic acid may have 8 to 20 carbon atoms, more preferably 8 to 14 carbon atoms, and may be terephthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, or a mixture of isophthalic acid and at least one selected from terephthalic acid, naphthalene dicarboxylic acid and diphenyl dicarboxylic acid.

[0052] The semiaromatic polyamide resin may also contain repeating units derived from aliphatic diamines. 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, more preferably 6 to 22 carbon atoms or 36 carbon atoms, most preferably 6 to 12 carbon atoms. Examples of linear aliphatic diamines are 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 branched aliphatic diamines are 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.

[0053] Suitable amino acids in the present invention preferably contain 4 to 12 carbon atoms. Examples of amino acids are 4-aminobutyric acid, 6-aminohexanoic acid, 7-aminoheptanoic acid, 8-aminooctanoic acid, 10-aminodecanoic acid, 11-aminoundecanoic acid and / or 12-aminododecanoic acid.

[0054] Suitable lactams in the present invention preferably contain 4 to 12 carbon atoms, more preferably 6 to 12 carbon atoms. Examples of lactams are 2-pyrrolidone (γ-butyrolactam), 2-piperidone (δ-valerolactam), ε-caprolactam, capryllactam, decanolactam, undecanolactam, enantholactam and / or laurolactam, preferably ε-caprolactam and / or undecanolactam.

[0055] In a preferred embodiment, the semi-aromatic polyamide resin comprises repeating units derived from a dicarboxylic acid comprising at least one aromatic dicarboxylic acid and a diamine comprising at least one aliphatic diamine.Preferably, the aliphatic diamine has 8 to 14 carbon atoms.

[0056] Preferably, the semi-aromatic polyamide resin is a polyphthalamide (PPA) resin, such as PA 4T, 5T, 6T, PA8T, PA9T, 10T or 12T, preferably PA 9T. Surprisingly, it was found that when PA9T is used, the resulting molded parts have good chemical resistance, low water absorption, good resistance to swelling, and have good dimensional stability, making them ideal as glove formers.

[0057] The semiaromatic polyamide resin in the present invention may also comprise a polyamide copolymer or a blend of two or more polyamides and copolyamides, such as PA 6T / 6I, PA 6T / 66, PA 6T / 8T, PA 6T / 10T, PA 6T / 10I, PA 10T / 10I, PA 6T / 9T, PA 6T / 12T, PA 4T / 6T / DT, PA 4T / 10T / DT, PA 4T / 4I / 6T / 6I / DT / DI, PA6T / 12T / 6I / 12I, PA 6T / 10T / 6I, PA 4T / 6T / 4I / 6I, PA 5T / 6T / 5I / 6I, PA 5T / 4T / 5I / 4I, PA 4T / 10T / 5I / 10I, PA 4T / 6T / DT, PA PA 4T / 10T / DT or PA 4T / 4I / 6T / 6I / DT / DI, preferably PA 6T / 6I, PA 6T / 10T, PA 6T / 12T, PA 6T / 10T / 6I, PA 6T / DT and / or PA 6T / DT / 6I / DI. In this context, D is 2-methyl-1,5-pentanediamine or 3-methyl-1,5-pentanediamine or a mixture thereof.

[0058] Based on the total amount of the semiaromatic polyamide resin composition, the preferred amount of the semiaromatic polyamide resin is 50-100 wt%, preferably 90-100 wt% when no filler is used; and 50-95 wt%, preferably 60-90 wt%, more preferably 70-85 wt% when a filler is used.

[0059] The semiaromatic polyamide resin composition may contain 0-50 wt % of a filler conventionally used in the art. There is no limitation on the form of the filler (eg, fiber, whisker, flake or particle).

[0060] The fiber can be, for example, an inorganic fiber, such as glass fiber, boron fiber, carbon fiber, silica fiber, ceramic fiber, wollastonite fiber, metal fiber, potassium titanate fiber, aluminum borate fiber and basalt fiber; organic reinforcing fiber, such as aramid fiber, polyester fiber, nylon fiber, polyethylene fiber; and natural fiber, such as wood fiber, flax fiber, hemp fiber and sisal fiber. Glass fiber, carbon fiber and aramid fiber are preferred. The fiber can be a short chopped fiber, for example, having a length of 2-500mm, preferably 3-200mm and a diameter of 5-40μm, preferably 10-25μm. The fiber filler in the polyamide composition preferably has an average length of 2-500μm, preferably 200-300μm, more preferably 220-240μm. The fiber can be present in an amount of 5-50wt%, preferably 10-45wt%, more preferably 15-35wt% based on the total weight of the composition. The fibers may be introduced by directly blending the chopped fibers with the semi-aromatic polyamide resin followed by extrusion, or by pultruding the long fiber bundles with the semi-aromatic polyamide resin followed by cutting. The fibers may also be surface treated (eg, treated with a silane coupling agent).

[0061] Alternatively, filler is used in the form of particles. Particulate filler can have a variety of particle sizes, ranging from particles in the form of dust to coarse particles. The particles used can include organic or inorganic particles. The example of usable material is inorganic particles, such as kaolin, chalk, wollastonite, talc, calcium carbonate, silicate, titanium dioxide, zinc oxide, graphite, mica, vermiculite, montmorillonite, glass particles (e.g., glass beads). The particles can also be surface treated fillers. The particle content can be 5-50wt%, preferably 10-45wt%, more preferably 15-35wt% based on the total weight of the composition.

[0062] In addition to fillers, the semi-aromatic polyamide resin composition may optionally contain other additives conventionally used in the art, such as lubricants, heat stabilizers, flame retardants, light stabilizers (UV stabilizers, UV absorbers or UV blockers), nucleating agents, pigments and dyes, antistatic agents, fluorescent brighteners, surface modifiers, flow modifiers, etc.

[0063] The additives may be used in a total amount of 0-10 wt%, preferably 0-5 wt%, more preferably 0-2 wt%, based on the total weight of the composition.

[0064] The lubricant comprises any one of stearates, titanates, stearic acid, erucamide, oleamide or silicones or a combination of at least two thereof. A very particularly preferred lubricant is calcium stearate, calcium montanate or aluminum stearate.

[0065] The heat stabilizer is preferably selected from copper compounds, aromatic secondary amines, sterically hindered phenols, phosphites, phosphonites and mixtures thereof.

[0066] Examples of suitable copper compounds are salts of monovalent or divalent copper with inorganic or organic acids or with mono- or difunctional phenols, monovalent or divalent copper oxides and complexes with ammonia, with amines, with amides, with lactams, with cyanides or phosphines, preferably Cu(I) or Cu(II) salts of hydrohalic acids or hydrocyanic acid, or copper salts of aliphatic carboxylic acids. Particularly preferred monovalent copper compounds are CuCl, CuBr, CuI, CuCN and Cu 2 O, and the divalent copper compound is particularly preferably CuCl 2 ,CuSO 4 , CuO, copper(II) acetate or copper(II) stearate.

[0067] An example of an aromatic secondary amine stabilizer is an adduct of phenylenediamine with acetone ( A), adducts of phenylenediamine and linolenic acid, or 4,4′-bis(α,α-dimethylbenzyl)diphenylamine ( 445), N,N'-dinaphthyl-p-phenylenediamine, N-phenyl-N'-cyclohexyl-p-phenylenediamine, or a mixture of two or more thereof.

[0068] 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.

[0069] Examples of phosphites and phosphonites are triphenyl phosphite, diphenyl alkyl phosphites, phenyl dialkyl phosphites, tris(nonylphenyl) phosphite, trilauryl phosphite, tritridecyl 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, diisodecyloxypentaerythritol diphosphite, bis(2,4-di-tert-butyl-6-methylphenyl)pentaerythritol diphosphite, bis(2,4,6-tri(tert-butylphenyl))pentaerythritol diphosphite Ester, tristearoyl sorbitol triphosphite, tetrakis(2,4-di-tert-butylphenyl)4,4'-biphenylene diphosphite, 6-isooctyloxy-2,4,8,10-tetra-tert-butyl-12H-dibenzo[d,g]-1,3,2-dioxaphosphocine, 6-fluoro-2,4,8,10-tetra-tert-butyl-12-methyldibenzo[d,g]-1,3,2-dioxaphosphocine, 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.

[0070] Examples of flame retardants are halogen-containing and halogen-free flame retardants and their synergists. Preferred halogen-free flame retardants are red phosphorus, phosphinates or bisphosphinates and / or nitrogen-containing flame retardants such as melamine, melamine cyanurate, melamine sulfate, melamine borate, melamine oxalate, melamine phosphate, trishydroxyethyl isocyanurate.

[0071] Examples of light stabilizers are resorcinols, salicylates, benzotriazoles and benzophenones, and also sterically hindered P-containing compounds, sterically hindered amines and carbodiimides.

[0072] The nucleating agent used may be sodium phenylphosphite, alumina, silica or talc, preferably talc.

[0073] The pigments used may be inorganic pigments, such as titanium dioxide, ultramarine blue, iron oxide, ZnO and boehmite, AlO(OH) and the like; organic pigments, such as phthalocyanine, quinacridone or perylene and the like. 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.

[0074] The preparation of the semiaromatic polyamide resin composition is achieved by methods known per se. This involves mixing the components in appropriate weight ratios. The components are preferably mixed at elevated temperatures by combining, mixing, kneading, extruding or rolling. The mixing temperature is preferably 300° C. to 350° C., in particular 310° C. to 340° C., in particular 320° C. to 340° C. Suitable methods are known to those skilled in the art.

[0075] In a preferred embodiment, the semi-aromatic polyamide resin composition comprises:

[0076] i) 50-95 wt%, preferably 60-90 wt%, more preferably 70-85 wt% of a semi-aromatic polyamide resin, preferably PPA;

[0077] ii) 5-50 wt%, preferably 10-45 wt%, more preferably 15-35 wt% of filler, and

[0078] iii) optional additives, preferably heat stabilizers.

[0079] In a more preferred embodiment, the semi-aromatic polyamide resin composition comprises:

[0080] i) 50-95wt%, preferably 60-90wt%, more preferably 70-85wt% PA9T;

[0081] ii) 5-50 wt%, preferably 10-45 wt%, more preferably 15-35 wt% of glass fibers, and

[0082] iii) optional additives, preferably heat stabilizers.

[0083] The molded part of the present invention

[0084] In another aspect, the present invention relates to a hollow molded part which is one-piece and has a main conduit at one end and a plurality of branches at the other end, the branches being connected to the main conduit, wherein the molded part is made of a semi-aromatic polyamide resin composition.

[0085] The dimensions of the main duct and the branches are as described above for the method for producing a molded part.In addition, there is also an inflection point in the main duct of the mold.

[0086] The hollow molded part can have 2 to 100, preferably 2-50, more preferably 2-20, most preferably 3-6 branches, for example, 2 branches, 3 branches, 4 branches, 5 branches, 6 branches. These branches can have the same or different lengths, preferably different lengths.

[0087] The wall thickness of the molded part can be adjusted as desired and may be, for example, 2-8 mm, preferably 2-5 mm, more preferably 3-4 mm.

[0088] The main conduit of the hollow molded part has an opening at the end away from the branch. The major axis of the opening can be the same as or slightly smaller than the end of the main conduit.

[0089] The main conduit may have a constant major axis in the length direction, or a variable major axis in the length direction, for example, a plurality of different major axes from the opening of the main conduit to the location of the branch. Preferably, the main conduit has a variable major axis in the length direction.

[0090] The molded part may have an inflection point (i) where there is a change in the trend of the major axis, which is the longer axis of each cross section of the main conduit along its length, or (ii) the junction of the main conduit and the nearest branch, if the major axes are of the same length.

[0091] If the major axes of the cross sections of the main conduit have different lengths, the inflection point means the point where the change trend of the major axis of each cross section of the main conduit along its length direction changes. For example, as observed from the opening, before the inflection point, the major axis of the main conduit changes from large to small, and after this point, the major axis of the main conduit changes from small to large. "Before" and "after" are only used to present relative positions, not to define specific positions. If the cross section of the main conduit is circular, the major axis corresponds to the diameter.

[0092] If the major axes of the cross-sections of the main conduit have the same length, the inflection point means the junction of the main conduit and the nearest branch.

[0093] In this context, the inflection point refers to the portion of the molded part that corresponds to the portion of the mold.

[0094] In one embodiment of the present invention, the molded part is a glove former. In this case, the hollow molded part has the shape of a glove. In particular, the molded part has the shape of a glove including a sleeve-shaped area, a palm-shaped area, and a finger-shaped area. The mold main conduit 2 is used to form the sleeve-shaped area and the palm-shaped area of ​​the glove, and the mold branches 6 are used to form the finger-shaped areas, and the number of branches is 5. The glove former usually has branches. The mold main 2 conduit can have a length and size corresponding to the sleeve-shaped area and the palm-shaped area of ​​the glove to be produced; the multiple branches can have different lengths and diameters corresponding to the finger-shaped areas.

[0095] In a more preferred embodiment, for the glove former, 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 less than or equal to 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=1:1-10:1, preferably, L2 / L1=1:1-3:1. The plane D0 is a plane in which the inflection joint is located and is perpendicular to the length direction of the mold main conduit 2.

[0096] In a more preferred embodiment, for a glove former, the thickness of the glove former is 2-5 mm, preferably 3-4 mm.

[0097] The semiaromatic polyamide resin compositions used are those described above for the process for producing the moulded parts.

[0098] Use of the molded part according to the invention

[0099] In a further aspect, the present invention relates to the use of the moulded part according to the invention or the moulded part obtainable by the process according to the invention as a dip former, preferably a glove former.

[0100] Dip former is a structural member that can model the shape of an object, and enables the dip molded part corresponding to the shape of the object to be molded. The dip molded part can be made by so-called dipping process. In such a process, the dip former is dipped into or immersed in a polymer emulsion (suitably rubber latex or vinyl polymer emulsion), and the polymer particles in the emulsion, more particularly the rubber particles in the latex, aggregate on the dip former and produce a coherent polymer film. The film will be in the shape of the dip former. In its simplest form, dipping is such a process, wherein thin-walled polymer (usually rubber) products are produced by the following steps: first the former is immersed in the polymer emulsion or rubber latex that has been properly compounded, and then the former is slowly taken out from the emulsion or latex, so that a uniform deposit is left on the former. If necessary, the thickness of the deposit can be increased by repeating the dipping and aggregation steps. Product molding is completed by leaching, drying and if necessary subjecting it to appropriate treatment, and the most obvious of these treatments is the vulcanization of rubber. The product may also be subjected to appropriate post-treatment. In many cases, it is a practice to form a curling edge at one or more of the open ends of the molded part. The main purpose of the curling edge is to strengthen the film and prevent tearing from the edge of the open end. This also prevents very thin-walled molded parts from adopting various distorted configurations. The product is usually removed from the former before use.

[0101] When the molded part of the present invention is used as a dip former, preferably a glove former, it has a surface quality comparable to that of conventional metal, ceramic or glass formers, but is lightweight and can withstand the glove production process involving high temperatures, mechanical handling and chemical exposure. Therefore, the molded part of the present invention has a long service life (typically more than 2 years) when used as a dip former, which is much longer than conventional ceramic molds (typically 0.5-1 year).

[0102] Examples

[0103] The present invention is further illustrated by the following examples, but the present invention is not limited thereto.

[0104] General Procedures

[0105] The semi-aromatic polyamide resin composition is Ultramid Advanced N3HG6LS BK from BASF, which is made of PA9T and 30% glass fiber and heat stabilizer.

[0106] The granular PA9T composition is next Injection molding at 330°C in a fluid-assisted injection machine. The mold is used to mold a glove former, and the mold temperature is 140°C. The semi-aromatic polyamide resin composition melt is injected for 3.5 seconds. Nitrogen injection is started 3.0 seconds after the start of resin composition injection. The nitrogen temperature is 23°C and the pressure is 1.8 MPa. The duration of nitrogen injection is 15 seconds. After the nitrogen injection is completed, the pressure in the mold cavity is kept constant for 10 seconds, and then the nitrogen is discharged. After the mold is cooled for 100 seconds, the mold is demolded and the molded part is removed. In this procedure, the resin inlet is located behind the fluid inlet and 3 cm away from the fluid inlet.

[0107] The mold used is Figure 2 , where the parameters are shown below:

[0108]

[0109] The molded part of Example 3 is Figure 3 , where the parameters are shown below:

[0110]

[0111] The thickness of the molded parts is in the range of 2-4 mm.

[0112] Comparative Example 1

[0113] The molded part was produced according to the general procedure described above, wherein the fluid inlet was located at 1 / 5 of the distance L2 from the plane D0, i.e., LF=42 mm. The L1 of the first branch (corresponding to the thumb) was 60 mm, and the L5 of the fifth branch (corresponding to the little finger) was 80 mm, which is only about half of the L1 and L5 of the molded part produced in Example 3. The L3 of the second branch (corresponding to the index finger) was 147 mm, and the L4 of the fourth branch (corresponding to the ring finger) was 181 mm. L2 (corresponding to the middle finger) was 206 mm.

[0114] Comparative Example 2

[0115] Comparative Example 1 was repeated, except that the fluid inlet was located at 1 / 3 of the distance L2 from plane D0, i.e., LF = 71 mm. L1 of the first branch (corresponding to the thumb) was 97 mm, and L5 of the fifth branch (corresponding to the little finger) was 131 mm, which is only about 3 / 4 of L1 and L5 of the molded part produced in Example 3. L3 of the second branch (corresponding to the index finger) was 177 mm, and L4 of the fourth branch (corresponding to the ring finger) was 151 mm. L2 (corresponding to the middle finger) was 207 mm.

[0116] Example 3

[0117] Comparative Example 1 was repeated, except that the fluid inlet was located at 1 / 2 of the distance L2 from the plane D0, ie, LF = 105 mm.

[0118] Results Evaluation

[0119] The surfaces of the molded parts obtained from Comparative Examples 1 and 2 and Example 3 were evaluated.

[0120] The surfaces of the molded parts obtained from Comparative Examples 1 and 2 and Example 3 were smooth and free from defects such as cracks, bubbles and pores, and no glass fiber was enriched on the surface. Each branch of the molded part obtained from Example 3 was completely filled, and the wall thickness was uniform. However, the molded parts obtained from Comparative Examples 1 and 2 were not completely filled, and the wall thickness was uneven.

[0121] The glove former of Example 3 was used in a factory to make nitrile rubber gloves and was found to have a useful life of over 2 years.

[0122] The molded parts produced by Example 3 had an alkaline corrosion rate of 0.012% in a 10 wt% NaOH solution and an alkaline corrosion rate of 0.012% in a 10 wt% HNO solution. 3 Acid corrosion rate in 0.018% solution. They are tested by immersing molded parts in acidic or alkaline solutions at room temperature and checking the weight change after 48 hours.

Claims

1. A method for producing a hollow molded part, the method comprising producing the hollow molded part by fluid-assisted injection molding, the method comprising 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), wherein the mold cavity (1) includes a mold main duct (2) and a plurality of mold branches (6) connected to the mold main duct (2), the resin composition is a semi-aromatic polyamide resin composition, the mold main duct (2) has an inflection point (i) at which the variation trend of the major axis changes, the major axis being the longer axis of each cross section of the mold main duct (2) along its length direction, or has (ii) a junction point between the mold main duct (2) and the nearest mold branch (6), if these major axes have the same length, Step (2): injecting a fluid into the molten resin composition via a fluid inlet (5) to obtain the molded part, wherein the fluid inlet (5) is located inside the mold main duct (2), and the distance LF from the fluid inlet (5) to a plane D0 is not less than 1 / 2 of the distance L2 from the plane D0 to the end of the longest mold branch (6), the plane D0 being a plane in which the inflection joint is located and perpendicular to the length direction of the mold main duct (2), Step (3): demoulding the molded part, The molded part is one-piece and has a main conduit at one end and a plurality of branches at the other end, the branches being connected to the main conduit, wherein the molded part is made of a semi-aromatic polyamide resin composition.

2. The method for producing a hollow molded part according to claim 1, wherein: The distance LF is not higher than 5 times L2, preferably not higher than 3 times L2.

3. A method for producing a hollow molded part according to claim 1 or 2, wherein: The fluid injection starts 0.5-15 seconds, preferably 0.5-10 seconds after the injection start time of the molten resin composition.

4. A method for producing a hollow molded part according to any one of claims 1 to 3, wherein: The duration of the fluid injection is 0.1-30 seconds, preferably 0.5-20 seconds, more preferably 5-20 seconds.

5. A method for producing a hollow molded part according to any one of claims 1 to 4, wherein: If the fluid is in gas form, the fluid pressure is 0.1-5 MPa, preferably 1-4 MPa, and if the fluid is in liquid form, the fluid pressure is 1-50 MPa, preferably 5-30 MPa; the fluid temperature is -30°C to 100°C.

6. A method for producing a hollow molded part according to any one of claims 1 to 5, wherein: At each end of a mold branch (6) of the mold there is an overflow cavity (4).

7. A method for producing a hollow molded part according to any one of claims 1 to 6, wherein: The ratio of the distance L2 from the plane D0 to the end of the longest branch to the distance L1 from the plane D0 to the end of the shortest branch is in the range of 1:1 to 10:1, preferably 1:1 to 3:

1.

8. A method for producing a hollow molded part according to any one of claims 1 to 7, wherein: The mold temperature during steps (1) and (2) was controlled in the range of 60°C to 160°C.

9. A method for producing a hollow molded part according to any one of claims 1 to 8, wherein: The semi-aromatic polyamide resin composition comprises at least one semi-aromatic polyamide resin comprising repeating units derived from an aromatic dicarboxylic acid, a diamine, and optionally other monomers such as an amino acid and / or a lactam.

10. The method for producing a hollow molded part according to any one of claims 1 to 9, wherein: The aromatic dicarboxylic acid has 8 to 20 carbon atoms, and is preferably selected from the group consisting of terephthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, or a mixture of at least one selected from terephthalic acid, naphthalene dicarboxylic acid and diphenyl dicarboxylic acid and isophthalic acid.

11. A method for producing a hollow molded part according to any one of claims 1 to 10, wherein: When no filler is used, the semi-aromatic polyamide resin is present in an amount of 50-100 wt %; and when a filler is used, the semi-aromatic polyamide resin is present in an amount of 50-95 wt %, in each case based on the total amount of the semi-aromatic polyamide resin composition.

12. A hollow molded part, wherein the hollow molded part is one-piece and has a main conduit at one end and a plurality of branches at the other end, the branches being connected to the main conduit, the molded part being made of a semi-aromatic polyamide resin composition.

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

14. The hollow molded part according to claim 12 or 13, wherein: The molded part has 2 to 100, preferably 2-50, more preferably 2-20, most preferably 3-6 branches.

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

16. The hollow molded part according to any one of claims 12 to 15, wherein The hollow molded part is a dip molder.

17. The hollow molded part according to claim 16, wherein The dip former is a glove former.

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