JPH03126751A - Polyoxymethylene resin composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition, having an ultrafine and homogeneous crystal structure and relaxed internal stress and capable of providing products excellent in mechanical strength, surface appearance and heat aging resistance by blending a polyoxymethylene resin with an aliphatic polyether and/or aliphatic polyester. CONSTITUTION:A polyoxymethylene resin composition obtained by blending (A) 100 pts.wt. polyoxymethylene resin prepared by copolymerizing trioxane with a cyclic ether compound selected from ethylene oxide, 1,3-dioxolane, 1,3- dioxepane, 1,3,5-trioxepane and 1,3,6-trioxocane and a compound selected from phenyl glycidyl ether, styrene oxide and naphthyl glycidyl ether with (B) aliphatic polyether and/or (C) an aliphatic polyester in an amount of 0.01-20 pts.wt., preferably 0.05-10 pts.wt.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a polyoxymethylene resin composition that has excellent mechanical properties and heat aging resistance7.More specifically, it has a high crystallization rate and low molding strain. Therefore, the present invention mainly relates to polyoxymethylene resin compositions for injection molding which have excellent mechanical properties and heat aging resistance.

<Prior Art> Polyoxymethylene resin is known as an engineering plastic with a good balance of mechanical strength and impact resistance, and is used in a wide range of fields as automobile parts and parts for electronic devices.

However, polyoxymethylene resin has extremely high crystallinity, and as a result, the spherulite structure that grows significantly especially when heat treated causes cracks and internal strain, thereby reducing the mechanical strength of the resin. Conventionally, as a method to refine and homogenize the crystal structure of polyoxymethylene resin, blending nucleating agents made of various inorganic compounds, organic compounds, and polymeric compounds with polyoxymethylene resin has been carried out. . For example, as an inorganic nucleating agent,
Polyoxymethylene resin compositions containing talc (Japanese Patent Publication No. 48-8254) and polyoxymethylene resin compositions using branched or linear polyoxymethylene as a nucleating agent are known. (Tokuko Showa 5)
5-19942). Further, a composition of a branched or networked polyoxymethylene and a polymer having a softening point below polyoxymethylene and an average molecular weight of 1,000 to 1,000,000 is also known (Japanese Patent Publication No. 42623/1983).
.

<Problems to be Solved by the Invention> However, the resin compositions described in Japanese Patent Publication No. 48-8254, Japanese Patent Publication No. 55-19942, and Japanese Patent Publication No. 5642623 have problems with the crystal structure of the obtained molded product. Due to insufficient miniaturization and homogenization, as well as insufficient relaxation of internal strain, a decrease in mechanical strength during heat treatment becomes a problem. It does not satisfy high durability.

<Means for Solving the Problems> As a result of intensive studies by the present inventors to solve the above problems,
A resin composition made by blending aliphatic polyether and/or aliphatic polyester with polyoxymethylene resin has an extremely fine and homogeneous crystal structure, and has mechanical strength, surface appearance, and reduced internal strain. It was discovered that a molded product with excellent heat aging resistance can be obtained, and the present invention was achieved.

That is, the present invention provides at least one compound selected from (a) trioxane and (b) ethylene oxide, 1.3-dioxolane, 1.3-dioxepane, 1.3.5-trioxebane, 1.3.6-) rioxocane. A polyoxymethylene resin obtained by copolymerizing a cyclic ether compound and (c) at least one compound selected from phenyl glycidyl ether, styrene oxide, and naphthyl glycidyl ether Group polyether [■] and/or aliphatic polyester [
(2) A polyoxymethylene resin composition containing 0.01 to 20 parts by weight of F is provided.

The method for producing the polyoxymethylene resin [I] of the present invention is not particularly limited. For example, component (a) trioxane and (
b) Components ethylene oxide, 13-dioxolane,
1,3-dioxolane, 1.3.5-trioxebane,
At least one selected from 1,3.6-trioxocane
After dissolving or suspending a cyclic ether compound and at least one compound selected from phenyl glycidyl ether, styrene oxide, and naphthyl glycidyl ether as component (c) in an organic solvent such as cyclohexane, a Lewis acid catalyst is added. It can be produced by adding and polymerizing, and decomposing and removing unstable ends. Preferably, there is a method of producing by bulk polymerizing using a self-cleaning stirrer without using any solvent, deactivating the catalyst with a hindered ane compound, and then decomposing and removing unstable terminals. As the Lewis acid catalyst, boron trifluoride, boron trifluoride hydrate, and coordination compounds of boron trifluoride and organic compounds having oxygen or sulfur atoms are preferably used. The amount of Lewis acid catalyst added is trioxane 100
0.001 to 0.00% by weight. The range is preferably 1 part by weight, particularly preferably 0.005 to 0.05 part by weight. In addition, the bulk polymerization reaction temperature is 6O~120℃
The temperature range is preferably from 60 to 90°C, particularly preferably from 60 to 90°C. The hindered amine compounds that deactivate the catalyst are bis(1,2,2,6,6-bentamethyl-4-bibeυdinyl) sebacate, bis(2,26,6-tetramethyl-4-piperidyl) sebacate, and succinate. dimethyl acid-
1-(2-hydroxyethyl-2,2,6゜6tetramethylbiperidine polycondensate, 1-[2-[3-(3,5-
di-t-butyl-4-hydroxyphenyl)propionyloxyconityl]-4-[3-(3,5-di-t-
[butyl-4-hydroxyphenyl)propionyloxy] 2,2,6,6-tetramethylbiperidine, etc., which has a hindered atom skeleton in the molecule, and the amount added is determined by the boron atom of the catalyst. It is preferable to add an amount equivalent to 0.1 to 20 nitrogen atoms in the hindered azine compound.

The polyoxymethylene resin of the present invention [(b) in
Ingredients ethylene oxide, 1,3-dioxolane, 1
, 3-dioxepane, 1,3.5-trioxebane, 1
, 3.6- at least one selected from the trio kumquats
The amount of the copolymerized cyclic ether compound is from 0 to 20 parts by weight, preferably from 0.21 to 7 parts by weight, based on 100 parts by weight of l-ricaxane (a). 0.
If the amount is less than 0.01 parts by weight, thermal stability will decrease, and if it is more than 20 parts by weight, it will be difficult to obtain a polymer with excellent mechanical strength, which is not preferred.

Polyoxymethylene resin of the present invention [(c) in I
The copolymerized amount of at least one compound selected from phenylglycidyl ether, styrene oxide, and naphthylglycidyl ether as components is preferably 0.001 to 10 parts by weight based on 100 parts by weight of trioxane as component (a). Preferably it is in the range of 0.01 to 5 parts by weight.

If the amount is less than 0.001 parts by weight, the effect of improving molding strain relaxation will be small, and if it is more than 10 parts by weight, the impact strength will decrease, which is not preferable.

The degree of polymerization of the polyoxymethylene resin [I] of the present invention is 8
Using pellets dried for 3 hours in a hot air oven at 0°C, temperature 190°C, according to ASTM D1238.
The MI value measured at a load of 2190 g is preferably in the range of 1 to 60 g/min.

If the MI value is less than 1 g/min, fluidity during injection molding decreases, making it impossible to mold a thin-walled molded product, which is not preferable. Moreover, if it exceeds 80 g/min, the degree of polymerization will be low and impact strength will become a problem, which is not preferable.

The aliphatic polyether []I] used in the present invention is
Poly(ethylene oxide) glycol, poly(propylene oxide) glycol, poly(tetramethylene oxide) glycol, poly(ethylene oxide/propylene oxide) glycol, poly(ethylene oxide/tetramethylene oxide) glycol, ethylene oxide adduct of poly(propylene oxide) glycol and derivatives thereof.

The average molecular weight of the aliphatic polyether [n] is 100
It is preferably in the range of 50'000 to 50'000, particularly preferably 1000 to 30000. If the average molecular weight is less than 100, the aliphatic polyether will bleed onto the surface of the molded product, reducing its commercial value, which is not preferable. Moreover, if it is 5000O or more, the relaxation of mold strain is small and the mechanical strength is greatly reduced, so it is not used.

Furthermore, the aliphatic polyester [11[
] means a polyester consisting of an aliphatic dicarboxylic acid having 4 to 20 carbon atoms and an aliphatic diol having 2 to 10 carbon atoms, or a polyester obtained by ring-opening polymerization of lactones, specifically poly(ethylene adipate), poly(butylene adipate), poly(ethylene sebacate), poly(butylene sebacate), poly(ε-caprolactone)
Examples include.

The average molecular weight of the aliphatic polyester [I[[] is 1
It is preferably in the range of 00 to 50,000, particularly preferably in the range of 1,000 to 30,000. If the average molecular weight is less than 100, the aliphatic polyester will bleed onto the surface of the molded product, reducing its commercial value, which is not preferable. Moreover, if it is 50,000 or more, the relaxation of molding strain is small and the mechanical strength is greatly reduced, so it is not used.

In the present invention, by adding aliphatic polyether and/or aliphatic polyester to polyoxymethylene resin, molding distortion is alleviated and a polyoxymethylene resin with excellent surface appearance, crystallinity, mechanical strength, and heat aging resistance is produced. Oxymethylene resin is obtained. It is important to add aliphatic polyether [n] and/or aliphatic polyester [I];
] and/or aliphatic polyester [■] O' is added in an amount of 01 to 20 parts by weight per 100 parts by weight of the polyoxymethylene resin [I], preferably 0.05 parts by weight.
~10 parts by weight. If it is less than 0.01 part by weight, the effect of improving molding distortion is small, and if it is more than 20 parts by weight, mechanical strength, represented by tensile strength, decreases, which is not preferable.

As a method for producing the polyoxymethylene resin composition of the present invention, generally known methods can be employed. For example, in the polymerization or stabilization step of polyoxymethylene resin [I], a method of adding aliphatic polyether [■] and/or aliphatic polyester [II], a method of adding polyoxymethylene resin [I], aliphatic polyether [■Co and/or aliphatic polyester [■Co] may be mixed in the form of pellets, powder, or granules and melt-processed as is, but melt-mixing using a Banbury mixer, roll, extruder, etc. may also be used. can. Particularly preferred is a method of melt-mixing at a temperature of 150 to 250° C. using a single-screw or twin-screw extruder.

In addition, the composition of the present invention may contain fillers such as calcium carbonate, barium sulfate, clay, titanium oxide, silicon oxide, mica powder, glass peas, carbon fibers, and glass fiber ceramics to the extent that the effects of the present invention are not impaired. Reinforcing agents such as Tsuku fiber, aramid fiber, potassium titanate fiber, coloring agent (
(pigments, dyes), nucleating agents, plasticizers, mold release agents such as ethylene bisstearoate, polyethylene wax, conductive agents such as carbon black, hindered phenolic compounds, thioether compounds, phosphite compounds, etc. Antioxidants, light stabilizers such as hindered compounds, benzophenone compounds, benzotriazole compounds, formaldehyde scavengers such as melacin, guanidine, nylon, dicyanthiade, adhesives, lubricants,
Additives such as a hydrolysis resistance improver and an adhesion aid may optionally be included.

<Example> The present invention will be explained below with reference to Examples. Note that all percentages and parts in the examples are based on weight.

Further, the mechanical properties, MI value, polymer melting point, crystallization temperature, and heat aging resistance of the molded articles shown in Examples and Comparative Examples were measured as follows.

・Injection molding: Using an injection molding machine with an injection capacity of 5 ounces, the ASTMI dumbbell test piece and Izotsu impact test piece were injected at a cylinder temperature of 190°C, a mold temperature of 65°C, and a molding cycle of 50 seconds. Molded. On this occasion,
The appearance of the ASTMI dumbbell test piece was visually observed.

- Mechanical properties 2 Using the ASTM No. dumbbell test piece obtained by the above injection molding, tensile strength was measured according to the ASTM-De38 method, and using an Izotsu impact test piece, the ASTM
1- Impact strength was measured according to the D-25El method.

- MI value: Measured according to ASTM-D 1238 at a temperature of 190°C and a load of 2180 grams using a pellet dried in a hot air oven at 80°C for 3 hours.

・Melting point (Tm), crystallization temperature (Tc): Using a differential scanning calorimeter (DSC), the temperature was raised from 80°C to 220°C at a rate of 10°C/min in a nitrogen atmosphere for 5 minutes at 220°C.
After the temperature was maintained at 10°C, the temperature was lowered at a rate of 10°C/min, and the crystallization temperature was measured. Furthermore, after cooling to 110°C, l
The melting point was measured by increasing the temperature at a rate of 0° C./min.

・Heat aging resistance; AST obtained by the above injection molding
The No. MI dumbbell was placed in an oven set at 150°C, taken out after a predetermined period of time, and its tensile strength was measured according to ASTM-D638 method.

Reference Examples The polyoxymethylene resins used in Examples and Comparative Examples were manufactured in the following manner.

Trioxane, (
Continuous polymerization was carried out by supplying 100 ppm of boron trifluoride diethyl etherate (2.5% benzene solution) and methylal as a polymerization degree regulator to the compound of component b), the compound of component (c), and trioxane. I did this. The polymerization temperature was controlled by controlling the outer jacket temperature at 60° C. with hot water, and the rotation speed was 80 rpm. Methyral as a molecular weight regulator was dissolved in trioxane.

(b) A premixing zone was provided so that the active compound and the catalyst solution were premixed immediately before being supplied to the kneader. The polymer was obtained as a white fine powder.

For 10 kg of single powder obtained in this way, 27 g
After deactivating the catalyst by adding a solution of bis(1,2,6,6-bentamethyl-4-piperidinyl) sebacate dissolved in 200 ml of benzene, 10 g of calcium stearate and 1,6-hexanethiol ruby were added. Sue[:3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] [Cibba Geigy (cib
Irganox (Irgan) manufactured by a-Geigy)
ox)" 50 g of 245 was added and stirred for 10 minutes in a Henschel driller. The resulting mixture was
Illφ, L/D=30 using a vented twin-screw extruder, cylinder temperature 230°C, vent vacuum degree 5 To
After melting and stabilizing under the conditions of rr, the mixture was discharged into water and cut to obtain pellet-shaped polyoxymethylene resin.

・Examples 1 to 9 and Comparative Examples 1 to 2 Polyoxymethylene resin produced according to Reference Examples
, and aliphatic polyether III] and aliphatic polyester [I [l], 45wφL/D=
31. ! The mixture was melt-kneaded at 220° C. in a vented twin-screw extruder No. 5, and discharged into water and cut to obtain pellets.

Table 1. ~Table 2. Polyoxymethylene resin [I
The types and blending ratios of aliphatic polyether [I], aliphatic polyester [I[], and the obtained physical properties are shown. Table 1. ~Table 2. As a result, the composition of the present invention has an excellent surface appearance, a small difference between the melting point (Tm) and the crystallization temperature (Tc), and therefore has excellent crystallinity.
It is also clear that it has excellent mechanical strength and heat aging resistance.

Margin 6 below - <Effects of the Invention> The composition of the present invention has excellent crystallinity, surface appearance of molded products, and heat aging resistance, so it can be used to produce electrical/electronic parts and automobiles by extrusion molding or injection molding, especially injection molding. It can be used in a wide range of parts, etc.

Claims (1)

[Claims] (a) trioxane and (b) ethylene oxide, 1,3
-dioxolane, 1,3-dioxebane, 1,3,5-
Obtained by copolymerizing at least one cyclic ether compound selected from trioxebane and 1,3,6-trioxocane and (c) at least one compound selected from phenyl glycidyl ether, styrene oxide, and naphthyl glycidyl ether. Polyoxymethylene resin [
I ] 100 parts by weight, aliphatic polyether [II]
and/or aliphatic polyester [III] 0.01~
A polyoxymethylene resin composition containing 20 parts by weight.