JP3136607B2 - Polyoxymethylene resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD OF THE INVENTION

TECHNICAL FIELD The present invention relates to a polyoxymethylene resin composition having excellent impact resistance and mechanical properties, and further having excellent surface appearance and heat aging resistance.

2. Description of the Related Art Polyoxymethylene resins are known as engineering plastics having a good balance between mechanical strength and impact resistance, and are used in a wide range of applications as automobile parts and electronic equipment parts. However, polyoxymethylene resins have extremely high crystallinity, and as a result, spherulite crystals that have grown significantly, especially when subjected to heat treatment, cause cracks and internal strain, thereby reducing the mechanical strength of the resin. As a method of miniaturizing and homogenizing the spherulite structure of polyoxymethylene resin, conventionally, a nucleating agent composed of various inorganic compounds, organic compounds, and high molecular compounds has been blended into the polyoxymethylene resin. I have. For example, as an inorganic nucleating agent,
Polyoxymethylene resin compositions to which talc has been added (JP-B-48-8254) and polyoxymethylene resin compositions in which branched or reticulated polyoxymethylene is used as a nucleating agent (JP-B-55-825). No. 19942). Also, a method of blending a thermoplastic polyurethane to improve the impact resistance of polyoxymethylene resin (Japanese Patent Publication No.
JP-155452, JP-B-59-155453, JP-A-61-155
No. 19652) is known.

[Problems to be solved by the invention]

However, JP-B-48-8254 and JP-B-55
The resin composition described in -19942, the fineness of the spherulite structure of the obtained molded article, homogenization, and insufficient relaxation of internal strain, the mechanical strength during heat treatment is reduced However, it has not been possible to satisfy the higher durability required for applications such as parts for electric / electronic devices and automobile parts. In addition, regarding the impact resistance, the above-mentioned JP-B-59-155452,
In the methods described in JP-B-59-155453 and JP-A-61-19652, the spherulite of the polyoxymethylene resin is not sufficiently refined and homogenized, so that the impact resistance is improved. However, the other mechanical properties were sharply reduced, and the impact resistance was not sufficiently satisfactory. Therefore, an object of the present invention is to obtain a polyoxymethylene resin composition having an excellent balance between mechanical strength and impact resistance.

[Means for Solving the Problems]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, a resin composition obtained by blending a thermoplastic polyurethane with a polyoxymethylene resin having a specific copolymer composition has a polyoxymethylene as a base. Since the resin has an extremely fine and homogeneous spherulite structure, it has been found that a molded article having a highly excellent balance of mechanical strength and impact resistance, and further excellent surface appearance and heat aging resistance can be obtained. The invention has been reached. That is, the present invention provides (a) trioxane and (b) ethylene oxide,
A polyether obtained by copolymerizing at least one cyclic ether compound selected from dioxolane, 1,3-dioxepane, 1,3,5-trioxepane, 1,3,6-trioxocan and (c) phenylglycidyl ether; An object of the present invention is to provide a polyoxymethylene resin composition containing 1 to 150 parts by weight of a thermoplastic polyurethane [II] based on 100 parts by weight of an oxymethylene resin [I].

BEST MODE FOR CARRYING OUT THE INVENTION

The method for producing the polyoxymethylene resin [I] of the present invention is not particularly limited. For example, trioxane of component (a) and ethylene oxide of component (b), 1,3-dioxolane,
Dissolving at least one cyclic ether compound selected from 1,3-dioxepane 1,3,5-trioxepane and 1,3,6-trioxocan and phenylglycidyl ether (c) in an organic solvent such as cyclohexane. Alternatively, the suspension can be produced by adding a Lewis acid catalyst, polymerizing the mixture, and decomposing and removing unstable terminals. Preferably, a method in which bulk polymerization is carried out using a self-cleaning type stirrer without using any solvent, the catalyst is deactivated with a hindered amine-based compound, and then the unstable terminal is decomposed and removed to produce the product is mentioned. As the Lewis acid catalyst, boron trifluoride, boron trifluoride hydrate, and a coordination compound of an organic compound having an oxygen or sulfur atom and boron trifluoride are preferably used. The amount of the Lewis acid catalyst to be added is usually preferably in the range of 0.001 to 0.1 part by weight, based on 100 parts by weight of trioxane,
Particularly preferably, it is in the range of 0.005 to 0.05 part by weight. Also, the bulk polymerization temperature is preferably in the range of 60 to 120 ° C,
Particularly, the range of 60 to 90 ° C is preferable. Hindered amine compounds that deactivate the catalyst include bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, Dimethyl succinate-1- (2-hydroxyethyl-2,2,6,6-tetramethylpiperidine polycondensate, 1- [2- [3- (3,5-di-t-butyl-4-hydroxyphenyl) ) Propionyloxy] ethyl] -4
A compound having a hindered amine skeleton in a molecule such as-[3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpiperidine. It is preferable to add an amount corresponding to 0.1 to 20 nitrogen atoms in the hindered amine compound per one boron atom of the catalyst. (B) at least one selected from ethylene oxide, 1,3-dioxolan, 1,3-dioxepane, 1,3,5-trioxepane, and 1,3,6-trioxocan in the polyoxymethylene resin [I] of the present invention; The copolymerization amount of the cyclic ether compound is usually 0.01 to 20 parts by weight, preferably 0.1 to 20 parts by weight, based on 100 parts by weight of the trioxane (a).
It is 1 to 7 parts by weight. If the amount is less than 0.01 part by weight, the thermal stability decreases, and if it exceeds 20 parts by weight, it is difficult to obtain a polymer having excellent mechanical strength, which is not preferable. The copolymerization amount of (c) phenylglycidyl ether in the polyoxymethylene resin [I] of the present invention is as follows:
Usually, with respect to 100 parts by weight of the trioxane of the component (a),
0.001 to 10 parts by weight is preferred, and particularly preferably 0.01 to 5 parts by weight.
It is in the range of parts by weight. If it is less than 0.001 part by weight, the effect of improving molding strain is small, and if it exceeds 10 parts by weight, impact strength is undesirably reduced. The degree of polymerization of the polyoxymethylene resin [I] of the present invention is as follows:
Using pellets dried in a hot air oven at 80 ° C. for 3 hours, according to ASTM D1238, temperature 190 ° C., load 2160 g
It is preferable that the MI value is in the range of 1 to 60 g / 10 minutes. If the MI value is less than 1 g / 10 minutes, the fluidity during injection molding decreases, and a thin-walled molded product cannot be molded. On the other hand, if it exceeds 60 g / 10 minutes, the degree of polymerization is lowered, and the impact strength becomes a problem. The thermoplastic polyurethane [II] used in the present invention may have any composition, but needs to exhibit thermoplasticity. Generally, a thermoplastic polyurethane comprises a hard segment and a soft segment having a urethane bond. The hard segment having a urethane bond is derived from a reaction between a diol and a diisocyanate. The diol is, for example, ethylene glycol, 1,2-
Examples include propanediol, 1,3-propanediol, 2,3-butanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol. Examples of the diisocyanate include 4,4'-methylenebis (phenylisocyanate) and 1,6-hexamethylene diisocyanate. The soft segment is composed of polyester diol or polyether diol.
Examples of the polyester diol include polyethylene adipate and polytetramethylene adipate.
Examples of the polyether diol include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. Among them, a thermoplastic polyurethane composed of a hard segment composed of 4,4'-methylenebis (phenylisocyanate) and ethylene glycol or 1,4-butanediol and a soft segment composed of polytetramethylene adipate or polytetramethylene glycol is described. preferable. The addition amount of the thermoplastic polyurethane [II] is 1 to 150 parts by weight, preferably 5 to 100 parts by weight, per 100 parts by weight of the polyoxymethylene resin [I]. If it is less than 1 part by weight, the effect of improving the impact resistance is small, and if it exceeds 150 parts by weight, the mechanical strength is undesirably reduced. As a method for producing the polyoxymethylene resin composition of the present invention, a generally known method can be employed. For example, in the polymerization or stabilization step of the polyoxymethylene resin [I],
The method of adding the thermoplastic polyurethane [II], the polyoxymethylene resin [I], and the thermoplastic polyurethane [II] may be mixed in the form of pellets, powder, or granules, and may be melt-processed as it is. A method of melt-mixing with a roll, an extruder or the like can also be adopted. Particularly preferably, using a single-screw or twin-screw extruder, at 150 to 250 ° C.
Is preferred. Further, the composition of the present invention contains calcium carbonate, barium sulfate, clay, titanium oxide, silicon oxide, mica powder, fillers such as glass beads, carbon fiber, glass fiber, ceramic within a range not impairing the effects of the present invention. Reinforcing agent such as fiber, aramid fiber, potassium titanate fiber, coloring agent (pigment, dye), nucleating agent, plasticizer, release agent such as ethylenebisstearylamide, polyethylene wax, conductive agent such as carbon black Antioxidants such as hindered phenol compounds, thioether compounds and phosphite compounds, light stabilizers such as hindered amine compounds, benzophenol compounds and bendtriazole compounds, melamine, guanazine, nylon and dicyandiamide. Formaldehyde scavengers, adhesives, such as
Additives such as a lubricant, a hydrolysis resistance improver, and an adhesion aid can be optionally contained.

【Example】

Hereinafter, the present invention will be described by way of examples. All percentages and parts in the examples are on a weight basis. In addition, the mechanical properties, MI value, crystal size of the polyoxymethylene resin and the molded product shown in Examples and Comparative Examples,
The heat aging resistance and the surface appearance were measured as follows. Injection molding: Using an injection molding machine with an injection capacity of 5 ounces, cylinder temperature 190 ° C, mold temperature 65 ° C, molding cycle 50 seconds, ASTM No. 1 dumbbell test piece, 1/2 inch width × 1 /
A 4 inch thick bending test piece and a 1/2 inch wide × 1/2 inch thick Izod impact test piece were injection molded. At this time, ASTM1
The appearance of the No. dumbbell specimen was visually observed. -Mechanical properties: ASTM-D7 using the bending test piece obtained by the above injection molding.
The flexural modulus was measured by a three-point beam method with a span of 100 mm and a strain rate of 3 mm / min according to the 90 method, and the impact strength was measured using an Izod impact test piece according to the ASTM-D256 method. -MI value: Measured at a temperature of 190 ° C and a load of 2160 g according to ASTM-D1238 using pellets dried in a hot air oven at 80 ° C for 3 hours.・ Spherulite size: 5 mg of the polyoxymethylene resin composition is sandwiched between cover glasses, heated on a hot stage, melted at 230 ° C. for 1 minute, and then cooled to 130 ° C. at 10 ° C./minute to form spheres. The crystals were observed under a polarizing microscope and further photographed to determine the crystallinity. -Heat aging resistance: 150 pieces of ASTM No. 1 dumbbell specimen obtained by the above injection molding
The sample was left standing in an oven set at ℃, taken out after a predetermined time, and measured for tensile strength according to the ASTM-D638 method to find the time at which the strength retention was 50%. Reference Example The polyoxymethylene resin [I] used in Examples and Comparative Examples was produced by the following method. 100mmφ, Cylinder Length (L) / Cylinder Diameter (D) = 10 Biaxial continuous mixer (“KRC manufactured by Kurimoto Iron Works, Ltd.
Kneader "S-4 type", trioxane which is a component compound (a), 1,3-dioxolane which is a compound of component (b),
(C) 100 ppm of boron trifluoride diethyl etherate (2.5% benzene solution) and methylal as a polymerization degree regulator were supplied to the component compounds phenylglycidyl ether and trioxane, respectively, to carry out continuous polymerization.
The polymerization temperature was controlled at an outer jacket temperature of 60 ° C. with warm water, and the rotation speed was 60 rpm. Methylal as a molecular weight regulator was dissolved in trioxane. Also,
A premix zone was provided so that the catalyst solution of the component (b) compound was premixed immediately before being supplied to the kneader.
The polymer was obtained as a white fine powder. To 10 kg of the fine powder thus obtained, a solution prepared by dissolving 27 g of bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate in 200 ml of benzene was added to deactivate the catalyst. After performing, further calcium stearate 10
g, 1,6-hexanediol-bis- [3- (3,5-di-
50 g of t-butyl-4-hydroxyphenyl) propionate (“Irganox” 245, manufactured by Ciba-Geigy) was added and stirred in a Henschel mixer for 10 minutes. The obtained mixture was 35 mmφ, L / D = 3
Using a twin screw extruder with vent of 0, cylinder temperature 230
After the melt stabilization was performed at a temperature of 5 ° C. and a degree of vacuum of 5 torr, the mixture was discharged into water and cut to obtain a pellet-like polyoxymethylene resin. In Examples and Comparative Examples, thermoplastic polyurethane [II]
The following, commercially available as -Milactran E180 (manufactured by Nippon Milactran): Adipate type. -Miractran E380 (manufactured by Nippon Miractran): ether type. -Milactolane E598 (manufactured by Nippon Milactran): Caprolactone type.・ Milactran E660 (manufactured by Nippon Milactran): Adipate type. [Examples 1 to 8 and Comparative Examples 1 to 4] Polyoxymethylene resin [I] and thermoplastic polyurethane [II] produced according to the reference example were dry-blended, and 45 mmφ, L / D = 31.5 vented biaxial. The mixture was melt-kneaded at 200 ° C. in an extruder, and was discharged and cut into water to obtain pellets. Tables 1 and 2 show the types and mixing ratios of the polyoxymethylene resin [I] and the thermoplastic polyurethane [II] used, and the obtained physical properties.

[Table 1]

[Table 2] From the results shown in Tables 1 and 2, the composition of the present invention shows that the base polyoxymethylene resin has an extremely fine and homogeneous spherulite structure, and therefore the thermoplastic polyurethane is blended to provide the mechanical strength and resistance to the composition. It is evident that the impact strength is excellent and the surface appearance and the heat aging resistance are also excellent.

【The invention's effect】

The composition of the present invention is highly excellent in the balance between mechanical strength and impact resistance, and further excellent in surface appearance and heat aging resistance, so that electrical and electronic equipment parts and automobiles requiring high strength and durability are required. It can be widely used as parts.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-214714 (JP, A) JP-A-59-145243 (JP, A) JP-A-59-145244 (JP, A) (58) Field (Int. Cl. ⁷ , DB name) C08L 59/00-59/04

Claims (1)

(57) [Claims] (1) (a) trioxane and (b) ethylene oxide, 1,3-dioxolan, 1,3-dioxepane, 1,3,5
-Trioxepane, at least one cyclic ether compound selected from 1,3,6-trioxocan and (c) 100 parts by weight of a polyoxymethylene resin [I] obtained by copolymerizing phenylglycidyl ether, A polyoxymethylene resin composition containing 1 to 150 parts by weight of a plastic polyurethane [II].