JPH09324106A - Polyacetal resin composition and molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyacetal resin composition having high melt tension important for blow-molding, exhibiting excellent blow-moldability and giving a molded article having excellent appearance, impact resistance, chemical resistance, etc. SOLUTION: This composition is composed of (A) 90-99.5wt.% (based on A+B) of a branched or crosslinked polyacetal resin having a melt index(MI) of 0.05-1.8g/10min (190 deg.C, 2,160g load) and (B) 10-0.5wt.% (based on A+B) of a polyolefin resin. The polyolefin resin B is dispersed in the composition in the form of rods.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyacetal resin composition excellent in molding processability, particularly blow moldability and its physical properties, and a molded product thereof.

[0002]

2. Description of the Related Art Polyacetal resin has a good balance of mechanical properties, chemical resistance, slidability, etc., and is easy to process. It is widely used mainly for various machine parts, but most of them are injection molded products. On the other hand, in recent years, the chemical resistance of polyacetal resin, especially the excellent resistance to organic solvents, has been expected to be applied to hollow parts related to automobile fuel tanks or engine rooms, and various containers. Blow molding is generally used as an efficient means for manufacturing such hollow molded parts, but blow molding is possible, and the drawdown property during molding and the formation of breakage and uneven thickness during blow are prevented. In order to improve the property, it is generally a necessary condition to increase the melt tension of the resin. Polyacetal resin can be used for general molding such as injection molding even if it has a relatively low molecular weight and low viscosity, but it has a low melt tension for blow molding and its molding is difficult, so simply increase the molecular weight. However, even if the melt viscosity is increased, a polyacetal resin having a general linear structure cannot be used to obtain a sufficient melt tension, and blow molding is extremely difficult. Therefore, by forming a branched or crosslinked structure in the molecule of the polyacetal resin,
There are examples of attempts to improve the melt tension of the resin, but simply forming a branched / crosslinked structure is still insufficient to improve the melt tension, and in order to obtain sufficient melt tension, it is even higher. In this case, it is necessary to increase the molecular weight and increase the degree of branching / crosslinking. In this case, the flowability deteriorates and molding efficiency is impaired, impact resistance is poor, and speckled unevenness is likely to occur on the surface of the molded product. Defects were also a big problem.

[0003]

In view of such circumstances, the present invention has a high melt tension, which is important for blow molding, has excellent blow moldability, has a good appearance, and has impact resistance characteristics,
An object of the present invention is to provide a polyacetal resin composition excellent in chemical resistance and the like and molded articles thereof.

[0004]

As a result of intensive studies aimed at achieving the above object, the present inventors have found that a specific polyacetal resin composition can solve the above problems, and have completed the present invention. That is, the present invention provides (A) a melt index (MI) of 0.05 to 1.8 g / 10 min (190 ° C,
Branched or cross-linked polyacetal resin with a load of 2160 g)
A composition comprising 90 to 99.5% by weight (vs. A + B) and (B) 10 to 0.5% by weight (vs. A + B) of a polyolefin resin, in which (B) the polyolefin resin is dispersed in a rod shape. And a blow molded polyacetal resin composition, and a hollow molded article thereof.

The composition of the present invention is characterized by forming a composition in which a specific polyacetal resin (A) is used as a matrix and at least a part or most of the polyolefin resin (B) maintains a rod-like dispersed shape. By virtue of this, the effect intended by the present invention is remarkably exhibited, and the formation of such a dispersed form is obtained by the various conditions described below, particularly by specifying the polyacetal resin.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the polyacetal resin composition of the present invention will be described. The branched or crosslinked polyacetal (A) used in the present invention has a conventionally known oxymethylene unit (--CH ₂ O--) as a main constituent element and has a branched or crosslinked structure, and the main chain of the molecule is other than the oxymethylene unit. All of those in which the comonomer is introduced and those in which the block component is introduced are also included. The branched or crosslinked polyacetal (A) used in the present invention has a melt index (MI) of 0.05 to 1.8 g / 10 min, particularly preferably 0.1.
~ 1.5 g / 10 min. Here, the melt index (MI) is a value measured at 190 ° C. and a load of 2160 g in accordance with ASTM D-1238. This melt index value (MI)
Is too much or too little from the above range, it is difficult for the polyolefin resin (B) to form a rod-shaped dispersion as described below, the melt tension cannot be sufficiently improved, the blow moldability is deteriorated, and the surface condition of the molded product is It is not preferable in terms of physical properties. Particularly preferred branched or crosslinked polyacetal resin in the present invention (A)
Is a melt index value (10 × MI) measured under a load of 10 times (21,600 g) and the above MI, in the range of 20 to 60, preferably 25 to 50. (10 x MI) / M
The I ratio mainly changes depending on the degree of branching or crosslinking of the polyacetal resin, and of course in the case of a linear molecular structure,
When the degree of branching (crosslinking) is small, it is less than 20, which is not preferable, and when the degree of branching (crosslinking) is excessive, it is more than 60, which is not preferable. By adjusting such viscosity characteristics, the olefin resin (B) used in combination is preferable for forming a rod-like dispersed form, and contributes to blow moldability such as melt tension and properties of the hollow molded article. Such viscosity characteristics can be obtained by adjusting the molecular weight of the polyacetal resin and the degree of branching or crosslinking thereof, as described below. The branched or crosslinked polyacetal in the present invention is, for example, (1) a polymer using a specific compound capable of forming a branched or crosslinked structure, using trioxane as a main monomer, and a cyclic ether or a cyclic formal as a comonomer, ( 2) A polymer using formaldehyde as a main monomer, a cyclic ether or a cyclic formal as a comonomer, and a specific compound capable of forming a branched or crosslinked structure, (3) formaldehyde or trioxane as a main monomer, and further branched. Or, a polymer using a specific compound capable of forming a crosslinked structure, and the like can be mentioned, but generally only a linear polyacetal polymer and a copolymer having substantially no widely used branched or crosslinked structure are used. The effect of the present invention cannot be obtained.

A particularly preferred branched or crosslinked polyacetal resin (A) in the present invention comprises trioxane as a main monomer, a cyclic ether or a cyclic formal as a comonomer, and a specific compound capable of forming a branched or crosslinked structure. , A polyacetal resin copolymerized in the presence of a cationic active catalyst such as boron trifluoride or its coordination compound or various protonic acid catalysts. Further, in order to adjust and stabilize the molecular weight during the polymerization, it is preferable to use a chain transfer agent such as a low molecular weight linear acetal such as methylal having an alkoxy group at both terminals which does not form an unstable terminal. As comonomers, cyclic ethers or cyclic formal, for example, ethylene oxide, propylene oxide, 1,3-dioxolane, 1,3-dioxane,
One or more kinds of 1,4-butanediol formal, diethylene glycol formal, trioxepane and the like can be mentioned, and the amount thereof is 0.2 to trioxane.
A range of 10% by weight is preferred. As the component capable of forming a branched or crosslinked structure, a polyfunctional compound having at least two epoxy rings or cyclic ether groups such as dioxolane rings in one molecule or a cyclic formal group is preferable, and
Polyhydric alcohols having at least 3 or more hydroxyl groups in one molecule can also be used, and these may be used alone or in combination of two or more. As such a polyfunctional compound,
For example, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, hexamethylene glycol diglycidyl ether, resorcinol diglycidyl ether, bisphenol A diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol Diglycidyl ether such as diglycidyl ether and polybutylene glycol diglycidyl ether; triglycidyl ether such as glycerin triglycidyl ether and trimethylolpropane triglycidyl ether; tetraglycidyl ether such as pentaerythritol tetraglycidyl ether; or the glycidyl ether of the above examples Instead of a group such as a merylidene glyceryl ether group Compounds having a cyclic formal group, and further polyhydric alcohols such as glycerin, trimethylolpropane, sorbitan monoester, diglycerin monoester, pentaerythritol, diglycerin, sorbitan, fructose, glucose, sorbitol and their alkylene oxide adducts Among these, a bifunctional compound having two cyclic ether groups or cyclic formal groups such as an epoxy ring or a dioxolane ring in one molecule is preferable. These compounds are preferably used in an amount of 0.005 to 0.2% by weight, more preferably 0.01 to 0.15% by weight, based on trioxane. The amount of such a branching or cross-linking component is involved in the degree of branch formation, and also serves as a factor that regulates the molecular weight and the degree of branching of the polymer together with the amount of the chain transfer agent. This is effective for improving the melt tension, improving the blow moldability, and further improving the properties of the molded article, which is the object of the present invention, by contributing to the dispersion form of

Next, as the polyolefin resin (B) used in the present invention, one selected from high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, ultra low density polyethylene and polypropylene, or Two or more kinds are mentioned, and a copolymer mainly composed of these and having a part thereof introduced with another olefin or a vinyl-based monomer such as an α, β-unsaturated carboxylic acid or an alkyl ester thereof is also included. The melt index value (MI) of these polyolefin resins (B) is not particularly limited, but is 0.1 to 100 g / 10 min, preferably
0.1 to 50 g / 10 min (in accordance with ASTM D-1238, 19
(Value measured at 0 ° C and a load of 2160 g). The content of the polyolefin resin (B) is 10 to 0.5% by weight (vs. A + B), preferably 5 to 0.5% by weight. Polyolefin resin
If the blending amount of (B) is too large, the original properties of the polyacetal resin are impaired, the impact resistance is lowered, and further the chemical resistance and solvent resistance are lowered, which is not preferable for the purpose of the present invention. On the other hand, when the amount of the polyolefin resin (B) is too small, sufficient melt tension cannot be obtained, so drawdown is likely to occur during blow molding, and moldability cannot be improved. Is insufficient, which is not preferable in any case. When the amount of the polyolefin resin (B) is within the above range, the effect can be obtained unexpectedly even with a small amount.

The composition of the present invention or a molded article thereof has a branched or crosslinked polyacetal resin (A) as a matrix,
This is characterized in that the polyolefin resin (B) is dispersed in a rod-shaped (including needle-shaped, fibrous, etc.) stretched state, which is obtained by adjusting the above-mentioned conditions. And by maintaining such a distributed form,
As will be shown in Examples below, the melt tension is improved to further improve the blow moldability, and the appearance and physical properties of the molded product can be appropriately maintained without causing problems such as peeling of the surface layer of the molded product. Is also extremely effective. The rod-like dispersion state of the polyolefin resin (B) can be confirmed by cutting the composition or the molded product in the resin flow direction and observing it with a scanning electron microscope (SEM). The composition of the present invention comprises at least 0.
5% by volume (vs. A + B) or more, preferably 0.8% by volume (vs. A)
It is preferable that + B) or more are dispersed in the shape of a rod extended with an aspect ratio (length / average diameter of the cross section in the direction perpendicular to the length direction) of 5 or more. Here, the amount of the polyolefin-based resin (B) dispersed in a rod shape (volume%; vs. A + B) is based on the entire rod-shaped (aspect ratio 5 or more) portion using the SEM photograph of the surface cut in the flow direction. It can be calculated from the area ratio.

The polyacetal resin composition of the present invention may optionally contain another thermoplastic resin, for example, a polyacetal (co) polymer having a substantially linear structure other than the component (A), as long as the object of the present invention is not impaired. Coalesced, polyurethane resin, (B)
Polyolefin-based resins, polyester-based resins, polyamide-based resins, polyether-based resins, and their modified products (elastomers) other than the components are supplementarily added in small amounts (for example,
(Within 30% by weight based on (A + B)) can be used together. Further, inorganic or organic fibrous reinforcing agents such as glass fibers, carbon fibers, potassium titanate fibers, and aramid fibers, powder fillers such as glass beads, carbon, calcium carbonate, talc, mica, glass flakes, etc. It is also possible to add one kind or two or more kinds of the fillers in the form of particles.
Further, the composition of the present invention further comprises various known additives to the polyacetal resin, such as antioxidants, heat stabilizers, various stabilizers such as light resistance (weathering) stabilizers, colorants such as dyes and pigments,
Lubricant, nucleating agent (crystallization accelerator), release agent, surfactant 1
One kind or two or more kinds can be mixed.

The composition of the present invention can be prepared by a commonly used general method. For example, each component is well mixed in advance with a blender such as a Henschel mixer, and a single-screw or multi-screw vented extruder is used. It is common to melt-knead and pelletize.

In the present invention, when a blow molded article is produced by blow molding using the above polyacetal resin composition, a molding machine used for blow molding of a general thermoplastic resin is used, and a conventionally known method is used. You can do it. Further, it is also possible to use a special molding machine such as a three-dimensional blow molding machine, and the polyacetal resin composition of the present invention has two or more layers, or a layer of another resin such as polyolefin, polyester or polyamide resin. It is also possible to perform multi-layer blow molding in combination with.

[0013]

The polyacetal resin composition of the present invention is
It has a high melt tension, which is important for blow molding, has excellent blow moldability, has a good appearance, and is also excellent in impact resistance. In addition, the polyacetal resin composition of the present invention has good mechanical properties and chemical resistance, and is used for hollow parts such as fuel tanks for automobiles or in the engine room, containers, piping materials such as pipes, and other various industrial applications. Can be widely used in.

[0014]

EXAMPLES The present invention will be specifically described below, but the present invention is not limited to these examples. The polyacetal resin used is as follows. Reference Example 1 (Branched (crosslinked) polyacetal resin POM-1
Preparation of a continuous mixing reactor composed of a barrel having a jacket through which a heat medium (warm water of 80 ° C.) is passed on the outside and two circles partially overlapping each other and a rotary shaft with a paddle, While rotating the two rotating shafts with paddles, at one end, 3.3% by weight of 1,3-dioxolane as a comonomer, 0.05% by weight of 1,4-butanediol diglycidyl ether as a branching (crosslinking) component, and a molecular weight Trioxane containing 0.04% by weight of methylal as a regulator is continuously supplied, and at the same time, a dibutyl ether coordination compound of boron trifluoride is continuously added as a catalyst to the same place,
Copolymerization was performed. Then, while rapidly passing the reaction product discharged from the polymerizer outlet through a crusher, an aqueous solution of 30 ° C. containing 0.1% triethylamine was added, and the mixture was crushed into fine particles and cooled at the same time to deactivate the catalyst and branch ( Or a crosslinked) crude polyacetal resin was obtained. Next, a stabilizer is added to this crude polyacetal resin, and the mixture is mixed using a Henschel mixer, and then mixed with a vented twin-screw extruder to 200
The mixture was melt-kneaded at 0 ° C. to stabilize it, and at the same time, a branched (crosslinked) polyacetal resin (POM-1) in the form of pellets was obtained. The melt index MI (according to ASTM D-1238, 190 ° C.) of the obtained resin is 1.0 g / 10 min [(10 × MI) / MI
= 36]. Reference Example 2 (Branched (crosslinked) polyacetal resin POM-2
Preparation) As a branching (crosslinking) component, 0.06 wt% of hexamethylene glycol diglycidyl ether was used instead of 0.05 wt% of 1,4-butanediol diglycidyl ether, and the amount of methylal was changed to 0.03 wt%. A branched (crosslinked) polyacetal resin (POM-2) was obtained in the same manner as in Reference Example 1 except for the above. The melt index MI of the obtained resin is 0.8 g / 10 min [(10 × MI) / MI = 40]
Met. Reference Example 3 (Branched (crosslinked) polyacetal resin POM-3
Preparation) A branched (crosslinked) polyacetal resin (P) was prepared in the same manner as in Reference Example 1 except that the amount of 1,4-butanediol diglycidyl ether used as a branched (crosslinked) component was changed to 0.04% by weight.
OM-3) was obtained. The melt index (MI) of the obtained resin is 1.5 g / 10 min [(10 × MI) / MI = 31]
Met. Reference Example 4 (Branched (crosslinked) polyacetal resin (POM-
Preparation of 4)) Use the amount of 1,4-butanediol diglycidyl ether used
A branched (crosslinked) polyacetal resin (POM-4) was obtained in the same manner as in Reference Example 1 except that the content was changed to 0.01% by weight. Melt index MI is 2.5g / 10min [(10 × MI)
/ MI = 20]. Reference Example 5 (Branched (crosslinked) polyacetal resin POM-5
Preparation of the amount of 1,4-butanediol diglycidyl ether used
A branched (crosslinked) polyacetal resin (POM-5) was obtained in the same manner as in Reference Example 1 except that 0.3% by weight and the amount of methylal used were changed to 0.09% by weight. The melt index MI of the obtained resin is 1.5 g / 10 min [(10 × MI) / MI
= 80]. Reference Example 6 (Preparation of linear polyacetal resin POM-6) In the same manner as in Reference Example 1 except that no branching / crosslinking agent was used and the amount of methylal used was changed to 0.05% by weight ( POM-6) was obtained. The melt index MI of the obtained resin is 2.0 g / 10 min [(10 ×
MI) / MI = 16]. The melt index MI was measured with a load of 2160 g, and 10 × MI was the load.
The value measured at 10 times (21600 g) is shown. The polyolefin resins used are as follows. POL-1: High density polyethylene, melt index
0.3g / 10min (Idemitsu Petrochemical Co., Ltd., Idemitsu Polyethylene 530B) POL-2: Low density polyethylene, melt index
20g / 10min (Sumitomo Chemical Co., Sumikasen G801) POL-3: Linear low density polyethylene, melt index 0.8g / 10min (Mitsubishi Chemical Co., Mitsubishi Polyethylene)
LL, UF421) POL-4: polypropylene, melt index 45
g / 10min (Sumitomo Chemical Co., Nobren X101A) POL-5: ethylene-ethyl acrylate copolymer, melt index 6g / 10min (Nihon Unicar Co., Ltd.,
NUC Copolymer DPDJ-6169) Examples 1-10, Comparative Examples 1-10 After mixing the components shown in Table 1 using a Henschel mixer, the cylinder temperature using a vented 30 mm twin-screw extruder 1
Each composition pellet was prepared by melt-kneading and extruding at 90 ° C. and pelletizing. Then, these pellets were used with a Capillograph 1B manufactured by Toyo Seiki Co., Ltd., and the orifice diameter was 1 m.
m, orifice length 10mm, temperature 190 ℃, extrusion speed 10mm / min
The melt tension (load) at the time of take-up was measured by a load cell under the conditions of (shear rate 122 sec ⁻¹ ) and take-up speed 20 m / min. The results are shown in Table 1. The dispersion shape of the polyolefin resin (B) on the cutting surface in the flow direction was observed using a scanning electron microscope (SEM) for the pellets, and the aspect ratio (length / average diameter in the direction perpendicular to the length direction was observed. (The thickness))
The ratio (area ratio) of the polyolefin-based resin having a ratio of 5 or more to the total (A + B) was determined, and when the ratio was 0.5% or more, it was bar-shaped, and when it was less than 0.5%, it was granular and the results are shown in Table 1.

Examples 11 to 14 and Comparative Examples 11 to 18 The resin compositions used in Examples 1, 2, 7, 9 and Comparative Examples 1 to 3 and 6 to 10 were blow molding machines (S-manufactured by Placo Co.). 45
ND), cylinder temperature 200 ℃, die temperature 200 ℃, mold temperature 80 ℃, blowing pressure 6 kg / cm ² , die diameter 30 mm, die clearance 2 mm, φ70 mm × 140 mm, thickness 1 mm water cylinder type The container was molded, and the drawdown tendency, the appearance of the molded product (spots, surface roughness), and the impact resistance were evaluated by the methods described below. Table 2 shows the results. The evaluation method is as follows. (1) Drawdown tendency Extrude from the blow molding machine until the length of the parison reaches 120 mm, measure the parison length after 10 seconds, and measure 130 mm or less as “fine”, 130 to 150 mm as “small”, and 150 mm or more. "Big"
And A parison that was cut and dropped by its own weight was designated as “DD”. The resin discharge rate was 500 g / min. (2) Appearance of molded product (spots, surface roughness) The surface of the molded product was visually evaluated for spots and surface roughness, and ranked as excellent, good, acceptable or poor. (3) Impact resistance 1.4% (500cc) of water was filled in a water bottle type blow molded product, and 1.4
From the height of m, drop it from the bottom of the container onto the concrete,
It was examined whether or not the container was broken by a drop impact. The evaluation was performed 10 times for each resin composition, and the following criteria were used:
It was ranked as excellent, good, acceptable and bad. Number of breaks 0 Excellent Number of breaks 1 piece Good Number of breaks 2 pieces Possible Number of breaks 3 pieces or more Bad

[0016]

[Table 1]

[0017]

[Table 2]

Claims (8)

[Claims] 1. (A) Melt index (MI) is 0.05
Branched or cross-linked polyacetal resin that is ~ 1.8 g / 10min (190 ℃, load 2160g) 90 ~ 99.5% by weight (vs. A + B)
And (B) polyolefin resin 10 to 0.5 wt% (vs. A +
A polyacetal resin composition comprising (B) a polyolefin resin dispersed in a rod shape. 2. The polyacetal resin composition according to claim 1, wherein (A) the branched or crosslinked polyacetal resin has a (10 × MI) / MI ratio of 20 to 60 (however, 10 × MI).
Is the melt index value measured under a load of 10 times (21600 g)). 3. A branched or crosslinked polyacetal resin (A) comprising trioxane as a main monomer, a cyclic ether or a cyclic formal as a comonomer, and a compound having two or more functional groups as a branched (crosslinking) forming component. The polyacetal resin composition according to claim 1 or 2, which is a polyacetal copolymerized in the presence of a cationic active catalyst. 4. The branched or crosslinked polyacetal resin (A) contains 0.2 to 10% by weight of a cyclic ether or cyclic formal as a comonomer (relative to trioxane), and has at least two cyclic ether groups or cyclic formal groups as a branching component. The polyacetal resin composition according to any one of claims 1 to 3, which is a copolymer containing 0.005 to 0.2% by weight of the compound having (with respect to trioxane). 5. The main component of the (B) polyolefin resin is one or more selected from high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, ultra low density polyethylene, and polypropylene. The polyacetal resin composition according to any one of claims 1 to 4, which is a polymer or a copolymer. 6. (B) At least a polyolefin resin
6. The polyacetal resin composition according to claim 1, wherein 0.5% by volume (vs. A + B) or more is dispersed in a rod shape having an aspect ratio of 5.0 or more. 7. The polyacetal resin composition for blow molding according to claim 1. 8. A hollow molded article obtained by blow molding the polyacetal resin composition according to any one of claims 1 to 7.