JP5214362B2 - Polyacetal resin molded product - Google Patents

Description

  The present invention relates to a molded article made of a polyacetal resin composition having excellent durability in a stressed state in an acidic atmosphere.

  Polyacetal resin is excellent in mechanical properties, heat resistance, chemical resistance, electrical properties, and as an engineering plastic due to its easy molding process, automotive parts, electrical / electronic parts, various machines, building materials, functional miscellaneous goods, etc. This material is widely used in the field. However, since polyacetal resin is weak against acid, its use in an acidic atmosphere is severely restricted. In practice, its use is restricted only in a very low concentration acidic atmosphere.

  As an application field of such a polyacetal resin, for example, as an automobile part, since it is excellent in chemical resistance, particularly fuel resistance, it is in direct contact with fuel oil, such as a fuel transfer unit represented by a fuel pump module or the like. There are parts.

  On the other hand, in recent years, as fuel for automobiles, there is a movement to disseminate so-called biofuels derived from biological resources as a measure against global warming due to carbon dioxide emissions and as a measure against rising oil prices. However, since the fuel used for biodiesel fuel is produced from various plants and the like, there are many impurities such as organic acids, and acid substances due to deterioration are more likely to be generated than conventional diesel fuel (light oil). Therefore, it is required to use a material that has excellent acid resistance as well as fuel resistance for parts that come into direct contact with such a fuel.

  In addition, products that are integrally molded with complex shapes are increasing for the purpose of weight reduction by resinization and cost reduction by integration. In the case of such a molded product, the residual stress at the time of molding tends to remain in the molded product due to the change in thickness and the integration of ribs and pipes. In the case of a molded product having such residual stress, the product may be destroyed by stress relaxation failure due to contact with an acidic substance.

  The present invention is a molded article comprising a polyacetal resin composition, and has high durability against direct contact with a liquid having an acidic substance such as an organic acid or an inorganic acid in a state where stress is present in the molded article. The object is to provide a molded product. In particular, an object of the present invention is to provide an automobile part that has excellent durability even when directly in contact with an automotive fuel containing an acidic component.

  As a result of intensive studies to solve the above problems, the present inventors have found that the object can be achieved by a molded article made of a specific polyacetal resin composition, and have reached the present invention.

  That is, the present invention relates to (A) 100 parts by weight of polyacetal resin, (B) 0.1 to 3.0 parts by weight of hindered phenol antioxidant, (C) 0.001 to 3.0 parts by weight of nitrogen-containing compound, (D) fatty acid calcium The present invention relates to a molded article made of a polyacetal resin composition obtained by adding 0.1 to 3.0 parts by weight of salt and (E) 0.1 to 3.0 parts by weight of a lubricant, and used under stress in an acidic atmosphere.

  Molded parts made of the polyacetal resin composition of the present invention have very good acid resistance and stress relaxation properties. It also has sufficient mechanical strength and heat resistance. For this reason, it is suitable for molded articles that come into direct contact with a liquid containing an acidic component, for example, automotive fuel containing sulfur or acidic substances, in particular, parts that come into direct contact with biodiesel fuel.

Hereinafter, the present invention will be described in detail. The (A) polyacetal resin used in the present invention is a polymer compound having an oxymethylene group (-CH ₂ O-) as the main constituent unit, polyacetal copolymer consisting of a repeating unit of a substantially oxymethylene group, Examples include polyacetal copolymers containing a small amount of other structural units in addition to the oxymethylene group. Any of these can be used, but from the viewpoint of acid resistance, which is the object of the present invention, it is preferable to use a polyacetal copolymer as a base resin. The polyacetal copolymer is preferably a polyacetal copolymer obtained by copolymerizing a comonomer component in an amount of 0.5 to 30% by weight, particularly preferably a copolymer obtained by copolymerizing a comonomer component in an amount of 0.5 to 10% by weight. A polyacetal copolymer obtained by copolymerizing a comonomer component is excellent in acid resistance and can retain excellent thermal stability, mechanical strength, and the like. Moreover, the polyacetal copolymer may have not only a molecule having a linear structure but also a branched structure or a crosslinked structure.

  In producing such a polyacetal copolymer, a cyclic oligomer of formaldehyde represented by trioxane is used as a main monomer. As the comonomer component, a compound selected from cyclic ethers having at least one carbon-carbon bond and cyclic formals is used. Examples of such a comonomer include ethylene oxide, 1,3-dioxolane, diethylene glycol formal, 1,4-butanediol formal, 1,3-dioxane, propylene oxide, and the like.

  In the polyacetal resin (A) as described above, particularly in the polyacetal copolymer, the degree of polymerization is not particularly limited, and the degree of polymerization can be adjusted according to the purpose of use and molding means. The melt index (MI) measured at a temperature of 190 ° C. and a load of 2.16 kg is preferably from 1 to 100 g / 10 min, particularly preferably from 5 to 30 g / 10 min.

  When the melt index is smaller than 5 g / 10 min, the flowability is lowered during molding, resulting in an increase in residual stress of the molded product. When the molded product is left in an acidic atmosphere, cracks due to solvent cracks are likely to occur. On the other hand, when the melt index is higher than 30 g / 10 min, the molecular weight of the polyacetal resin is decreased, and the strength is greatly reduced when attacked by an acid in an acidic atmosphere.

  Examples of the (B) hindered phenol antioxidant used in the present invention include 2,2′-methylenebis (4-methyl-6-tert-butylphenol), hexamethylene glycol-bis (3,5-di-t). -Butyl-4-hydroxyhydrocinnamate), tetrakis [methylene (3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane, triethylene glycol-bis-3- (3-tert-butyl- 4-hydroxy-5-methylphenyl) propionate, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxy-benzyl) benzene, n-octadecyl-3 -(4'-hydroxy-3 ', 5'-di-t-butylphenol) propionate, 4,4'-methylenebis (2,6-di-t-butylphenol), 4,4'-butylidene-bis- (6 -T- Til-3-methyl-phenol), di-stearyl-3,5-di-tert-butyl-4-hydroxybenzylphosphonate, 2-tert-butyl-6- (3-tert-butyl-5-methyl-2-) Hydroxybenzyl) -4-methylphenyl acrylate, 3,9-bis {2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl} -2 4,8,10-tetraoxaspiro [5,5] undecane and the like.

  In the present invention, at least one or two or more selected from these antioxidants can be used.

  (B) The hindered phenol antioxidant preferably has a melting point of less than 100 ° C. Since the melting point is low, the mobility is improved in the polyacetal resin, and the antioxidant function is effectively exhibited against the oxidative attack on the surface of the molded product. Triethylene glycol-bis-3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate (melting point: about 77 ° C.) is a particularly preferred antioxidant.

  The addition amount of the (B) hindered phenol antioxidant in the present invention is 0.1 to 3.0 parts by weight with respect to 100 parts by weight of the (A) polyacetal resin. When the blending amount of the antioxidant (B) is small, not only the antioxidant property which is the original purpose becomes insufficient, but also the acid resistance which is the object of the present invention is inferior. When the blending amount of (B) antioxidant is excessive, undesirable effects such as mechanical properties and moldability of the resin composition occur.

  Examples of the (C) nitrogen-containing compound used in the present invention include melamine and derivatives thereof (including guanamine and derivatives thereof), melamine formaldehyde resins, hydrazide compounds, polyamides and polyacrylamides.

  First, melamine and its derivatives include melamine (2,4,6-triamino-sym-triazine), melem, melam, melon, N-butylmelamine, N-phenylmelamine, N, N-diphenylmelamine, N, N Diallyl melamine, N, N ", N" -trimethylol melamine, benzoguanamine (2,4-diamino-6-phenyl-sym-triazine), 2,4-diamino-6-methyl-sym-triazine, 2,4 -Diamino-6-butyl-sym-triazine, 2,4-diamino-6-benzyloxy-sym-triazine, 2,4-diamino-6-butoxy-sym-triazine, 2,4-diamino-6-cyclohexyl- sym-triazine, 2,4-diamino-6-chloro-sym-triazine, 2,4-diamino-6-mercapto-sym-triazine, 2,4-dioxy-6-mercapto-sym-triazine 2,4-Dioxy-6-amino-sym-triazine (Amelide), 2-oxy-4,6-Diamino-sym-Triazine (Ameline), N, N, N ', N'-Tetracyanoethylbenzoguanamine etc. are used Is done.

  As the melamine formaldehyde resin, a water-insoluble melamine-formaldehyde polycondensate is used which is produced from melamine and formaldehyde in a molar ratio of 1: 0.8 to 1: 10.0.

  Examples of the hydrazide compound include adipic acid hydrazide and sebacic acid hydrazide.

  Polyamides such as nylon 12, nylon 6,10, nylon 6,66,610, single or copolymerized polyamides, substituted polyamides with methylol groups, nylon salts, synthesized from caprolactam, or synthesized from caprolactone, caprolactam Polyester amide or the like to be used.

  As polyacrylamide, one or two or more of homopolymers of acrylamide, copolymers thereof, and cross-linked products are used. Among these, melamine, a derivative of melamine, and one or more selected from melamine formaldehyde resin are preferable, and further, it is produced from melamine and formaldehyde at a molar ratio of 1: 0.8 to 1: 10.0. It is particularly preferable to use a melamine formaldehyde resin which is a water-insoluble melamine-formaldehyde polycondensate.

  The amount of the (C) nitrogen-containing compound used in the present invention is preferably 0.001 to 3.0 parts by weight with respect to 100 parts by weight of the (A) polyacetal resin.

  In the present invention, (D) a fatty acid calcium salt is blended in order to dramatically improve acid resistance. (D) The fatty acid constituting the fatty acid calcium salt may be a saturated fatty acid or an unsaturated fatty acid. Also, those in which some hydrogen atoms are substituted with a substituent such as a hydroxyl group can be used. Examples of such fatty acids include monovalent or divalent fatty acids having 10 or more carbon atoms, such as monovalent saturated fatty acids having 10 or more carbon atoms [capric acid, lauric acid, myristic acid, pentadecylic acid, palmitic acid, stearic acid. C10-34 saturated fatty acids (preferably C10-30 saturated fatty acids) such as arachidic acid, behenic acid and montanic acid], monovalent unsaturated fatty acids having 10 or more carbon atoms [oleic acid, linoleic acid, linolenic acid, C10-34 unsaturated fatty acids such as arachidonic acid and erucic acid (preferably C10-30 unsaturated fatty acids)], divalent fatty acids having 10 or more carbon atoms (dibasic fatty acids) [sebacic acid, dodecanoic acid, tetradecanoic acid , Divalent C10-30 saturated fatty acids (preferably divalent C10-20 saturated fatty acids) such as tapsia acid, divalent C10-30 unsaturated fatty acids (preferably divalent C10-30 saturated fatty acids) such as decenedioic acid and dodecenedioic acid C10-20 not Sum fatty acids), etc.] can be exemplified.

  The fatty acid also includes fatty acids having one or more hydroxyl groups in the molecule (for example, hydroxy-saturated C10-26 fatty acids such as 12-hydroxystearic acid).

  Particularly preferred components (D) are calcium stearate, calcium 12-hydroxystearate, and calcium behenate.

  In the present invention, the amount of (D) fatty acid calcium salt added is 0.1 to 3.0 parts by weight with respect to 100 parts by weight of (A) polyacetal resin. The blending of the (D) fatty acid calcium salt greatly contributes to the improvement of acid resistance. (D) If the added amount of the fatty acid calcium salt is less than 0.1 parts by weight, the intended acid resistance cannot be obtained, and if it exceeds 3.0 parts by weight, the mechanical properties and the like are impaired.

  As the (E) lubricant used in the present invention, fatty acid esters and fatty acid amides are used.

  Examples of fatty acid esters include fatty acids having 12 to 32 carbon atoms such as lauric acid, palmitic acid, heptadecanoic acid, stearic acid, oleic acid, arachidic acid, and behenic acid, and monovalent aliphatics such as palmityl alcohol, stearyl alcohol, and behenyl alcohol. Alcohol, ester compounds with polyhydric aliphatic alcohols such as glycerin, pentaerythritol, dipentaerythritol, sorbitan, fatty acid and polybasic organic acid and monohydric aliphatic alcohol or polyhydric aliphatic alcohol compound ester compound, etc. Can be used. Examples of such fatty acid ester lubricants include cetyl palmitate, butyl stearate, stearyl stearate, stearyl citrate, glycerol monocaprylate, glycerol monocaprate, glycerol monolaurate, glycerol monopalmitate, glycerol dipalmitate. Tate, glycerol monostearate, glycerol distearate, glycerol tristearate, glycerol monooleate, glycerol dioleate, glycerol trioleate, glycerol monolinoleate, glycerol monobehenate, glycerol mono12-hydroxystearate, glycerol Di12-hydroxystearate, glycerol tri-12-hydroxystearate, glycerol diacetomonostearate, glycerol citrate fatty acid Ester, pentaerythritol adipate stearate, montanic acid partially saponified esters, pentaerythritol tetrastearate, dipentaerythritol hexastearate, sorbitan tristearate, and the like. These fatty acid ester lubricants can be used alone or in combination of two or more.

  The fatty acid amide-based lubricant is not particularly limited. For example, saturated fatty acid amides such as lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, hydroxystearic acid amide; oleic acid amide, erucic acid amide, ricinoleic acid amide, etc. Of N-stearyl stearic acid amide, N-oleyl oleic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, N-stearyl erucic acid amide, N-oleyl palmitic acid amide, etc. Amides; methylol amides such as methylol stearic acid amide and methylol behenic acid amide; methylene bis stearic acid amide, ethylene biscapric acid amide, ethylene bis lauric acid amide, ethylene bis stearic acid amide (ethylene bis Tealylamide), ethylene bisisostearic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisbehenic acid amide, hexamethylene bisbehenic acid amide, hexamethylene bishydroxystearic acid amide, N, N′-di Saturated fatty acid bisamides such as stearyl adipic acid amide and N, N′-distearyl sebacic acid amide; ethylene bisoleic acid amide, hexamethylene bisoleic acid amide, N, N′-dioleyl adipic acid amide, N, N′— Examples thereof include unsaturated fatty acid bisamides such as dioleyl sebacic acid amide; aromatic bisamides such as m-xylylene bisstearic acid amide and N, N′-distearylisophthalic acid amide.

  (E) The melting point of the lubricant is preferably less than 100 ° C. Since the melting point is low, a plasticizer effect is also exhibited in the polyacetal resin, and stress relaxation is easily promoted. Glycerol monostearate (melting point: about 67 ° C.), glycerin monopalmitate (melting point: about 67 ° C.), glycerin monobehenate (melting point: about 80 ° C.) and the like are particularly preferred lubricants.

  The amount of (E) lubricant added in the present invention is 0.1 to 3.0 parts by weight with respect to 100 parts by weight of (A) polyacetal resin. (E) When the blending amount of the lubricant is small, the original release property is insufficient, and when it is excessive, the biting property at the time of molding is inferior and it is difficult to obtain a good molded product.

  The molded product of the present invention is a conventional molding method using the polyacetal resin composition having the above-described configuration, for example, a method such as injection molding, extrusion molding, compression molding, blow molding, vacuum molding, foam molding, rotational molding, etc. Can be obtained by molding.

  The use is not particularly limited as long as it is a liquid containing an acidic component or a molded part that comes into direct contact with vapor. For example, automotive fuel containing sulfur or acidic substances, particularly biodiesel fuel or deteriorated diesel fuel. It can be applied to parts that come into contact.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto.
Examples 1 to 13 and Comparative Examples 1 to 5
To (A) polyacetal resin, (B) hindered phenol antioxidant, (C) nitrogen-containing compound, (D) fatty acid calcium salt, and (E) lubricant are added and mixed in the proportions shown in Table 1, and biaxial. A pellet-shaped composition was prepared by melt-kneading with an extruder. Details of the ingredients are as described below.

  Next, a flat plate of 80 mm × 80 mm × 1 mm was produced by injection molding using this pellet. A test piece for evaluation was prepared by cutting the formed flat plate into a width of 10 mm in the direction perpendicular to the flow, which is susceptible to stress. Stress relaxation and acid resistance were evaluated by the following methods. The results are shown in Table 1. Some materials were also evaluated for fuel resistance.

For comparison, compositions as shown in Table 2 were prepared and evaluated in the same manner. The results are shown in Table 2.
Test 1 (Evaluation of stress relaxation)
The specimen is left in an oven at 100 ° C. in a bent state with a strain of 2%, and the specimen surface is observed. The time when the crack was observed in the test piece is defined as the crack generation time. The higher the stress relaxation property, the longer the crack generation time.
Test 2 (Evaluation of acid resistance)
The specimen is bent at a strain of 1% and left in a 10 wt% aqueous hydrochloric acid solution at room temperature, and the specimen surface is observed. The time when the crack was observed in the test piece is defined as the crack generation time. The higher the acid resistance and stress relaxation properties, the longer the crack generation time.
Test 3 (Evaluation of fuel resistance)
Place the specimen in a test gas oil at 110 ° C (JIS2 diesel oil with 30% fatty acid ester and 0.04% acetic acid added) and observe the surface of the specimen in a bent state with 1.5% strain. . The time when the crack was observed in the test piece is defined as the crack generation time. The higher the light oil resistance and stress relaxation properties, the longer the crack generation time.
[Ingredients]
(A) Polyacetal resin Polyacetal copolymer obtained by copolymerizing 96.7% by weight of trioxane and 3.3% by weight of 1,3-dioxolane
a-1. Melt index (measured at 190 ℃, load 2160g) is 8.9g / 10min
a-2. Melt index is 26.5g / 10min
a-3. Melt index is 2.4g / 10min
a-4. Melt index is 44.6g / 10min
(B) Hindered phenolic antioxidant
b-1. Triethyleneglycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] (melting point: about 77 ° C)
b-2. Tetrakis [methylene (3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane (melting point: about 118 ° C.)
(C) Nitrogen-containing compounds
c-1. Melamine
(D) Fatty acid calcium salt and comparative metal compound
d-1.Calcium stearate
d-2.12-hydroxycalcium stearate
d-3.Calcium behenate
d-4. Sodium stearate
(E) Lubricant
e-1. Glycerol monostearate (melting point approx. 67 ° C)
e-2. Ethylene bis-stearic acid amide (melting point approx. 143 ° C)

Claims (4)

(A) For 100 parts by weight of polyacetal resin,
(B) hindered phenolic antioxidant 0.1-3.0 parts by weight,
(C) 0.001 to 3.0 parts by weight of melamine ,
(D) Fatty acid calcium salt 0.5 to 3.0 parts by weight, and
(E) A molded article comprising a polyacetal resin composition obtained by adding 0.1 to 3.0 parts by weight of a lubricant and used under stress in an acidic atmosphere.   The molded article according to claim 1, wherein either or both of (B) a hindered phenol-based antioxidant and (E) a lubricant have a melting point of less than 100 ° C.   The molded article according to claim 1 or 2, wherein the fatty acid calcium salt is any one of calcium stearate, calcium 12-hydroxystearate, and calcium behenate.   The melt index of (A) polyacetal resin is 5-30 g / 10min, The molded article of any one of Claims 1-3.