JP2517698B2 - Polyoxymethylene resin injection molding material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyoxymethylene resin injection molding material excellent in injection moldability, particularly high cycle property and mechanical properties.

More specifically, the polyoxymethylene resin is excellent in mechanical properties because it can be molded by shortening the cycle time due to the high solidification rate in the mold during injection molding, and the molding strain is small due to the small spherulite size. It relates to an injection molding material.

[Prior Art] Polyoxymethylene resins are known as engineering plastics having a good balance of mechanical strength and impact resistance, and are used in a wide range of fields as automobile parts and electronic device parts.

Most processing of polyoxymethylene resin is performed by injection molding. In this injection molding field, there is a strong demand for shortening the molding cycle, that is, improving productivity by so-called high cycle.

A method for increasing the cycle of a polyoxymethylene resin, which is a crystalline polymer, has been proposed in which a nucleating agent is added to increase the crystallization rate to accelerate the solidification rate in the mold. For example, JP-A-59-129247 and JP-B-55-1994.
Japanese Patent Publication No. 2 describes a method of using a polyoxymethylene resin having a branched structure as a nucleating agent. Further, Japanese Patent Publication No. 48825/1974 describes that an inorganic compound represented by talc is added as a nucleating agent.

[Problems to be Solved by the Invention] However, the above-mentioned JP-A-59-129247 and JP-B-Sho
The resin compositions described in JP-A-55-19942 and JP-B-48-8254 do not sufficiently improve the crystallization rate, so that satisfactory high cycle properties cannot be expected, and further, a molded product obtained. The improvement of mechanical strength due to the miniaturization and homogenization of the crystal structure of is not sufficient, and it does not satisfy the higher mechanical strength required for applications such as electric / electronic equipment supplies and automobile parts.

[Means for Solving the Problem] The present inventors have arrived at the present invention as a result of intensive studies to obtain a polyoxymethylene resin excellent in high cycle property and mechanical properties without adding a nucleating agent.

That is, the present invention comprises at least 100 parts by weight of (a) trioxane and (b) at least one selected from ethylene oxide, 1,3-dioxolane, 1,3-dioxepane, 1,3,5-trioxepane and 1,3,6-trioxocane. According to ASTM D1238, obtained by copolymerizing 0.01 to 20 parts by weight of one cyclic ether compound and 0.001 to 10 parts by weight of (c) at least one compound selected from glycidyl phenyl ether, styrene oxide and glycidyl naphthyl ether. , Temperature 190 ℃,
An injection molding material composed of a polyoxymethylene copolymer having a MI value of 1 to 60 g / 10 minutes measured under a load of 2160 g,
The melting point (Tm) of the polyoxymethylene copolymer and the temperature falling crystallization temperature (Tc) have a relationship of Tm-Tc <15 (° C), and the spherulite size is 10 μm or less. Polyoxymethylene resin injection molding material.

The method for producing the oxymethylene copolymer of the present invention is not particularly limited. For example, (a) component trioxane and (b)
At least one cyclic ether compound selected from ethylene oxide, 1,3-diosisolane, 1,3-dioxepane, 1,3,5-trioxepane, and 1,3,6-trioxocane, and glycidylphenyl as the component (c) After dissolving or suspending at least one compound selected from ether, styrene oxide, and glycidyl naphthiether in an organic solvent such as cyclohexane, Lewis acid catalyst is added to polymerize to decompose unstable terminals. It can be removed and manufactured. Preferred is a method in which bulk polymerization is carried out using a self-cleaning stirrer without using any solvent, the catalyst is deactivated with a hindered amine compound, and then unstable terminals are decomposed and removed. As the Lewis acid catalyst, boron trifluoride, boron trifluoride hydrate and a coordination compound of boron trifluoride with an organic compound having an oxygen or sulfur atom are preferably used. The amount of the Lewis acid catalyst added is 0.001 to 0.1 with respect to 100 parts by weight of trioxane.
The range of parts by weight is preferable, and particularly preferably 0.005 to 0.05.
The range is parts by weight. The bulk polymerization reaction temperature is 60 to 12
The range of 0 ° C is preferable, and the range of 60 to 90 ° C is particularly preferable. Hindered amine compounds that deactivate the catalyst include bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, succinate. Acid dimethyl-1- (2-hydroxyethyl-2,2,6,6 tetramethylpiperidine polycondensate, 1- [2- [3- (3,5-di-t-butyl-4-hydroxyphenyl) pro] Pionilioxy] ethyl] -4
-[3- (3.5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpiperidine Compounds having a bound amine skeleton in the molecule, such as This means that it is preferable to add an amount corresponding to 0.1 to 20 nitrogen atoms in the hindered amine compound with respect to 1 boron atom of the catalyst.

(B) in the polyoxymethylene copolymer of the present invention
The copolymerization amount of at least one cyclic ether compound selected from the component ethylene oxide, 1,3-dioxolane, 1,3-dioxepane, 1,3,5-trioxepane, 1,3,6-trioxocane is (a). The amount is 0.01 to 20 parts by weight, preferably 0.1 to 7 parts by weight, based on 100 parts by weight of the component (3). If it is less than 0.01 parts by weight, the thermal stability will decrease, and
If it exceeds the weight part, it is difficult to obtain a polymer having excellent mechanical strength, which is not preferable.

(C) in the polyoxymethylene copolymer of the present invention
The copolymer of at least one compound selected from the component glycidyl phenyl ether, styrene oxide and glycidyl naphthyl ether is 0.001 to 10 parts by weight, preferably 0.01 Is in the range of 5 parts by weight. If it is less than 0.001 part by weight, the effect of improving the high cycle property is small, and if it exceeds 10 parts by weight, the impact strength decreases, which is not preferable.

The degree of polymerization of the polyoxymethylene copolymer of the present invention is 80
Using pellets dried in a hot air oven at ℃ for 3 hours,
According to ASTM D1238, the MI value measured at a temperature of 190 ° C. and a load of 2160 g needs to be in the range of 1 to 60 g / 10 minutes. When the MI value is less than 1 g / 10 minutes, the fluidity at the time of injection molding is lowered, and a thin-walled molded product cannot be molded, which is not preferable.
If it exceeds 60 g / 10 minutes, the degree of polymerization is low and impact strength becomes a problem, which is not preferable.

In order for the polyoxymethylene resin injection molding material of the present invention to have excellent high cycle moldability and mechanical properties,
It is necessary that the melting point (Tm) of the polyoxymethylene copolymer and the falling crystallization temperature (Tc) have a relationship of Tm-Tc <15 (° C) and that the spherulite size is 10 μm or less. . When Tm-Tc is 15 ° C or higher, the solidification speed in the mold is slow, so the effect of shortening the molding time is small, and when the spherulite size exceeds 10 μm, the residual molding strain after injection molding is large and the mechanical properties are improved. It is not preferable because it lowers.

The melting point (Tm) and the temperature falling crystallization temperature (Tc) in the present invention are measured under a nitrogen atmosphere using a differential scanning calorimeter (DSC).
Raise the temperature from room temperature to 220 ℃ at a rate of 10 ℃ / minute, and 220 minutes for 5 minutes
After the temperature is kept at ℃, the temperature is lowered at a rate of 10 ℃ / min, the cooling crystallization temperature is measured, then the temperature is cooled to 100 ℃, the temperature is raised again at a rate of 10 ℃ / min, and the melting point is measured. did.

Also, the spherulite size is polyoxymethylene copolymer 10
After sandwiching mg between cover glasses and heating on a hot stage to melt for 5 minutes at 230 ° C, while observing with a polarizing microscope, the temperature was lowered to 130 ° C at a rate of 10 ° C / min, and the resulting crystals were photographed. Then, the method for determining the spherulite size was adopted.

In addition, the polyoxymethylene resin injection molding material of the present invention, to the extent that the object of the present invention is not impaired, known hindered phenol-based, phosphite-based, thioether-based,
Amine-based antioxidants, benzophenone-based, hindered amine-based weathering agents, melamine, dicyandiamide, polyamide, polyvinyl alcohol copolymer and other formaldehyde scavengers, fluorine-containing polymers, silicone oils, polyethylene wax, and other lubricants , Colorants such as dyes and pigments, UV shielding agents such as titanium oxide and carbon black, reinforcing agents such as glass fiber and carbon fiber potassium titanate, fillers such as silica, clay, calcium carbonate, calcium sulfate and glass beads. , Talc and other nucleating agents, flame retardants, plasticizers, adhesion aids,
An adhesive or the like can be optionally contained. Furthermore,
For the purpose of improving the mechanical strength of the polyoxymethylene copolymer of the present invention, another thermoplastic polymer or thermoplastic elastomer may be contained.

[Examples] The effects of the present invention will be described below with reference to Examples. In addition,
All percentages and parts in the examples are by weight.

The molding cycle and mechanical properties were measured as follows.

-Molding cycle: Using an injection molding machine with an injection capacity of 5 ounces, set the cylinder temperature to 190 ° C, the mold temperature to 60 ° C, the injection time to 5 seconds, and change the cooling time to obtain an 80 x 80 x 3 mmt square. When a plate was molded and the deformation by the four protruding pins placed the three vertices of the molded product on the flat plate, the cooling time was measured so that the deviation of the remaining one vertex from the flat plate was 1 mm or less.

-Mechanical properties: Using an injection molding machine with an injection capacity of 5 ounces, set the cylinder temperature to 190 ° C, mold temperature to 65 ° C, molding cycle to 50 seconds, ASTM No. 1, dumbbell test piece, and Izod impact test piece. Was injection molded. The obtained ASTM No. 1 dumbbell test piece was used to measure the tensile strength according to the ASTM D638 method, and the Izod impact test piece was used to measure the impact strength according to the ASTM D256 method.

Examples 1 to 10, Comparative Examples 1 to 5 100 mmφ, L / d = 10 biaxial continuous mixer ("KRC Kneader S-4 type" manufactured by Kurimoto Iron Works) with trioxane, compound of component (b), To the compound of component (c) and trioxane, 100 ppm of boron trifluoride diethyl etherate (2.5% benzene solution) and methylal as a polymerization degree regulator were respectively supplied to carry out continuous polymerization. The polymerization temperature was controlled to about 60 ° C by passing warm water through the outer jacket, and the rotation speed was set to 60 rpm. Methylal as a molecular weight regulator was dissolved in trioxane. or,
A premixing zone was provided so that the compound as the component (b) and the catalyst solution were 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 of 27 g of bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate in 200 ml of benzene was added to deactivate the catalyst. And then calcium stearate 10
g, 1,6-hexanediol-bis- [3,5-di-t-butyl-4-hydroxyphenyl) propionate] [Ciba-Geigy "Irganox (I
rganox) "245] Add 50 g and in a Henschel mixer 1
Stir for 0 minutes. The obtained mixture was heated at a cylinder temperature of 230 ° C. using a vented twin-screw extruder of 35 mmφ and L / D = 30.
After performing melt stabilization under the condition of the vent vacuum degree of 5 Torr,
The mixture was discharged into water and subjected to cutting to obtain a pelletized polychiocimethylene copolymer. The composition of the obtained polyoxymethylene copolymer was confirmed by 60 MHz ¹ H NMR (in a heavy hexafluoroisopropanol solvent). For example,
When glycidyl phenyl ether is used as the compound of the component (c), a multiplet signal peculiar to the phenyl group is detected at δ6.9-7.6 (ppm) in addition to the methylene group signal at δ4.3-5.2 (ppm). As a result, it was confirmed to be a glycidyl phenyl ether copolymer.
In addition, it was confirmed from the amount charged that the copolymer was quantitatively obtained from the integrated value. Table 1 shows the copolymerization composition and physical properties of the various polyoxymethylene copolymers thus obtained. From the results shown in Table 1, it is clear that the injection molding material of the present invention is excellent in injection moldability and mechanical properties.

[Effects of the Invention] The polyoxymethylene resin injection molding material of the present invention provides a polyoxymethylene resin molded product having a small molding strain and excellent mechanical properties because the spherulite size of the polyoxymethylene copolymer used is small. . Furthermore, Tm-Tc <15 (℃)
Therefore, since the cycle time at the time of injection molding can be shortened, it becomes possible to mass-produce polyoxymethylene resin molded products having excellent characteristics.

Claims (1)

(57) [Claims] 1. At least 100 parts by weight of (a) trioxane and (b) at least one selected from ethylene oxide, 1,3-dioxolane, 1,3-dioxepane, 1,3,5-trioxepane and 1,3,6-trioxocane. One kind of cyclic ether compound 0.01〜
20 parts by weight and (c) 0.001 to 10 parts by weight of at least one compound selected from glycidyl phenyl ether, styrene oxide, and glycidyl naphthyl ether, obtained by copolymerization, according to ASTM D1238, temperature 190 ° C., load 2160
An injection molding material comprising a polyoxymethylene copolymer having an MI value of 1 to 60 g / 10 minutes measured in g, wherein the melting point (Tm) and the crystallization temperature (Tc) of the polyoxymethylene copolymer are lowered. The relationship is Tm-Tc <15 (° C), and the spherulite size is 10 μm or less, a polyoxymethylene resin injection molding material.