JP3046449B2 - Polyacetal resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polyacetal resin (A)
In a resin composition containing, as a main component, a thermoplastic polyurethane resin (B) as an auxiliary component, the compatibility is improved, the impact resistance is improved, and a polyacetal resin composition having particularly high melt tension is provided. is there.

[0002]

BACKGROUND OF THE INVENTION Polyacetal resins are excellent in moldability and have well-balanced mechanical properties, electrical properties, heat resistance, solvent resistance, friction and wear properties, and the like. Because of its excellent fatigue resistance as a plastic material, it is used in a very wide field as a typical engineering resin. However, with the expansion of application fields, there is a tendency for the required performance of the resin to become more sophisticated and specialized.
Further improvement in impact resistance is desired. In addition, conventional polyacetal resins or their compositions generally have low melt tension, and are suitable for molding rods and films by extrusion molding, or for forming hollow molded products by blow molding, by drawing down at the time of melting. However, improvement of the melt tension is desired to improve such processability. In general, to increase the melt tension, it is conceivable to increase the molecular weight and improve the melt viscosity.However, there is a limit to the increase in the molecular weight, and even if the molecular weight can be increased, the shear viscosity also increases at the same time, and the moldability is increased. Exacerbated, extrusion and blow molding still have problems. From such a viewpoint, it is desired to develop a polyacetal resin composition having high melt tension and low shear viscosity at the same time as improving impact resistance. The present invention provides a polyacetal resin having improved impact resistance by a simple method, extrudability by further enhancing the melt tension at the time of melting, and a resin composition having significantly improved blow moldability. Aim. Conventionally, it has been known that the blending of a polyurethane-based resin is effective in improving the toughness and impact resistance of a polyacetal resin, and it is also necessary to improve and devise the dispersion form (for example, fine particle dispersion, network dispersion, etc.). Improvements in the effect have also been proposed, but all polyurethane-based resins have a separated two-phase structure with a clear interface in the polyacetal resin matrix. , And further improvement in toughness and impact resistance was desired, and in particular, almost no improvement in melt tension was observed.

[0003]

Means for Solving the Problems In view of the above problems, the present inventors have conducted intensive studies on the improvement of the dispersion state by melt-kneading a polyacetal resin (A) and a thermoplastic polyurethane resin (B). By melt-kneading a very small amount of a specific alkali metal or thallium salt (C) with the polyurethane resin (B), surprisingly, the phase of the polyacetal resin (A) and the thermoplastic polyurethane resin (B) is Improves solubility and obtains a dispersed form in which the two phases do not fuse together to form a clear interface, and has excellent chemical resistance, mechanical properties, and friction and wear properties inherent to polyacetal resin. And the like, and further improved impact resistance, and found that a particularly high melt tension was developed. That is, the present invention provides a polyacetal resin (A)
50 to 99 parts by weight and thermoplastic polyurethane resin (B) 50 to 1
100 parts by weight of a resin component comprising 100 parts by weight of an alkali metal salt or thallium salt of an aliphatic or aromatic carboxylic acid (C)
Was added blended 0.005 part by weight formed by melt-kneading, the molten
A polyacetal resin composition for extrusion molding or blow molding with improved tension .

Hereinafter, the components of the present invention will be described. The polyacetal resin used in the present invention (A), a polymer compound having an oxymethylene group (-CH ₂ O-) as the main constituent unit, a polyoxymethylene homopolymer, the other structural units in addition to oxymethylene groups Copolymer, terpolymer, block polymer may be contained in a small amount,
The molecule may have not only a linear shape but also a branched or crosslinked structure. The terminal group may be any as long as it is stable, and there is no particular limitation on the degree of polymerization, and those having moldability (for example, a melt flow value under a load of 190 ° C. and 2160 g with a load of 1.5 to 70 ). That is, either a commercially available product or a known polyacetal resin can be used.

[0005] The thermoplastic polyurethane resin (B) used in the present invention is a polymerization reaction product comprising the following components (i), (ii) and (iii). (i) diisocyanate compound (ii) high molecular weight polyol having a molecular weight of 500 to 5000 (iii) low molecular weight polyol having a molecular weight of 60 to 500 and / or
Or polyamine Here, the diisocyanate compound (i) constituting the thermoplastic polyurethane resin is, for example, 1,4-butylene diisocyanate, 1,6-hexamethylene diisocyanate,
Cyclopentylene-1,3-diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, cyclohexylene-1,4-diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,4 An isomer mixture of tolylene diisocyanate and 2,6-tolylene diisocyanate, 4,4′-methylenebis (phenyl isocyanate),
2,2-diphenylpropane-4,4′-diisocyanate,
p-phenylene diisocyanate, m-phenylene diisocyanate, xylene diisocyanate, 1,4-naphthylene diisocyanate, 1,5-naphthylene diisocyanate, 4,4'-diphenyl diisocyanate, azobenzene-4,4'-diisocyanate, m- or p -Tetramethylxylene diisocyanate and 1-chlorobenzene-2,4-diisocyanate. Preferably 4,4'-methylenebis (phenylisocyanate),
1,6-hexamethylene diisocyanate, 2,4-tolylene diisocyanate, isophorone diisocyanate and the like.

Next, the high molecular weight polyol (ii) which is a constituent component of the thermoplastic polyurethane resin has a molecular weight of 500 to 500.
0, preferably 1000 to 3000, is a component that forms a soft segment of the polyurethane resin. Such high molecular weight polyols mainly include polyester diols having hydroxyl groups at both ends (including polycarbonate diols),
It is a polyether diol or the like, and a small amount thereof may be a triol or the like. Suitable polyester diols are polyester diols of one or more dihydric alcohols with one or more dicarboxylic acids. Suitable dicarboxylic acids which make up this are adipic, succinic, sebacic, suberic, methyladipic, glutaric, azelaic, thiodipropionic and citraconic acids and mixtures containing small amounts of aromatic dicarboxylic acids. And the like. Suitable dihydric alcohols as other components include 1,3- or 1,2-propylene glycol, 1,4-butanediol, 1,3-butanediol, 1,5-diethylene glycol, 1,5 -Pentanediol, 1,6-pentanediol, 1,12-dodecanediol, and mixtures thereof. Furthermore, hydroxycarboxylic acids, lactones, and carbonates, such as ε-caprolactone and 3-hydroxybutyric acid, can also be constituents of the polyester diol. Preferred polyester diols belonging to this are polyadipate diols, polylactone diols and polycarbonate diols.
The preferred polyether diol belonging to (ii) is 1
One or more alkylene glycols, for example,
Condensation products such as ethylene glycol, 1,2- or 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, and mixtures thereof.
Particularly preferred polyether diols are poly (tetramethylene ether) glycol, poly (propylene oxide) glycol, copolymers of propylene oxide and ethylene oxide, and copolymers of tetrahydrofuran and ethylene oxide, more preferably poly (tetramethylene ether) glycol It is. Other suitable polymeric diols may be those whose backbone is predominantly hydrocarbon, such as polybutanediol.

Next, (iii) low molecular weight polyols and / or polyamines having a molecular weight of 60 to 500, which are constituents of the thermoplastic polyurethane resin, are mainly selected from aliphatic short-chain diols or diamines or aromatic diols or diamines. At least one or more of them may partially contain a small amount of triol. This component becomes a hard segment of the thermoplastic polyurethane resin,
It plays a role of crosslinking. Preferred low molecular weight polyols include ethylene glycol, propylene glycol, 1,2-ethanediol, 1,4-butanediol, 1,6-hexanediol, glycerin, hydroquinone diethylol ether, resorcin diethylol ether or derivatives thereof. is there. Examples of the polyamine include diphenylmethanediamine, m-phenylenediamine, and derivatives thereof. Such (i), (ii),
The thermoplastic polyurethane resin comprising the reaction product of (iii) comprises the low molecular weight polyol and / or polyamine (iii) in an amount within the range of about 0.2 to 5 equivalents to 1 equivalent of the high molecular weight polyol (ii). Polyurethane is preferred,
(ii) The more the component, the softer it becomes, which affects the hardness and toughness of the composition.

The mixing ratio of the polyacetal resin (A) and the thermoplastic polyurethane resin (B) is 1 to 50 parts (weight), preferably 3 to 40 parts (weight), based on 100 (parts by weight) of both. ). (B) The more the component, the softer and higher the toughness, which is selected according to the purpose. However, when it is too large, it is too soft, and when it is too small, the impact resistance intended by the present invention is lacking, and the melt tension is undesirably reduced.

Next, used as a characteristic component of the present invention,
Alkali metal salts or thallium salts of aliphatic or aromatic carboxylic acids (C) are alkali metals (Li, Na, K, Rb, Cs)
Or an aliphatic carboxylate or an aromatic carboxylate of thallium. The aliphatic carboxylic acid is a monovalent or divalent or higher carboxylic acid having 1 to 28 carbon atoms, for example, acetic acid,
And propionic acid, butyric acid, stearic acid and the like.
The aromatic carboxylic acid may be, for example, benzoic acid or a carboxylic acid having an aromatic ring, and in any case, may have a hydroxyl group or another substituent. Further, such a component may be a mixture of two or more kinds. The content of the metal salt (C) is 0.005 to 1 part by weight, preferably 0.01 to 0.5 part by weight, per 100 parts by weight of the resin component (A) + (B).

According to the study of the present inventors, if the polyacetal resin (A) and the thermoplastic polyurethane resin (B) are simply melt-kneaded, and the third substance is generally present, for example, the component (C) Even when an alkaline earth metal salt of a similar fatty acid (for example, calcium or barium salt) is added, when the dispersion form of the composition is observed with a microscope, the size of the dispersed particles,
Apart from the difference in shape, while both have a two-phase structure in which the interface between the two phases can be clearly identified, surprisingly, the alkali metal or thallium carboxylate (C) of the present invention can be used in an extremely small amount. By addition and melt-kneading, the dispersed form exhibits a fused form to the extent that the interface cannot be discriminated even if two phases are present. This means that when the fracture surface of the molded article is treated with an appropriate selective solvent, when the component (C) is not blended, a clear cavity in which the polyurethane phase is eluted is observed, whereas the component (C) is removed. It can also be seen from the fact that the polyurethane phase is completely covered by the polyacetal resin when it is blended, and the polyurethane phase is not eluted. It has been found that not only improvement in toughness and impact resistance can be obtained in response to the development of such a dispersion form, but also particularly significant improvement in melt tension.

Incidentally, the polyacetal resin composition of the present invention further comprises a conventionally known additive such as a lubricant, a lubricant, a nucleating agent, in order to impart desired properties within a range not impairing its purpose.
Additives such as dyes and pigments, release agents, antioxidants, heat stabilizers, weather (light) stabilizers, reinforcing agents, hydrolysis stabilizers, other thermoplastic resins and inorganic or organic fillers can be compounded. .

The composition of the present invention can be prepared by various known methods, but it is necessary to heat and melt in the presence of at least the above three components and to knead for at least 20 seconds. May be simultaneously used together, or may be separately added. Specifically, for example, polyacetal resin (A)
The thermoplastic polyurethane resin (B) and the alkali metal salt or thallium salt (C) are uniformly mixed in advance with a mixer such as a tumbler or Henschel mixer, and then supplied to a single- or twin-screw extruder for melt-kneading. There is a method using an open roll, a Banbury mixer, a kneader, etc., and further melt-knead the polyacetal resin (A) and the alkali metal salt or thallium salt (C) in advance, then blend the thermoplastic polyurethane resin (B) and melt. Kneading method, or melt-kneading the polyacetal resin (A) and the thermoplastic polyurethane resin (B) in advance, and then alkali metal salt or thallium salt
The method of adding and kneading (C) is more effective. After the resin composition kneaded by these methods is pelletized,
It may be subjected to molding or may be molded directly. The kneading temperature is 5 ° C. higher than the temperature at which the polyacetal resin component melts.
To 100 ° C higher, particularly preferably 10 ° C above the melting point.
It is a high temperature of 60 to 60 ° C If the temperature is too high, decomposition or abnormal reaction occurs, which is not preferable. The melt-kneading time is at least 20 seconds to 10 minutes, preferably 1 to 5 minutes.

[0013]

The composition of the present invention is a composition in which a thermoplastic polyurethane resin is extremely well fused with a polyacetal resin, has improved toughness and impact resistance, has a particularly high melt tension, and is extruded. The moldability such as blow molding is improved, and it is suitable for forming a film, a rod or a hollow molded article by these molding methods.

[0014]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto. Examples 1 to 5 and Comparative Examples 1 to 4 Polyacetal resins (Polyplastics Co., Ltd., Duracon) shown in Table 1, thermoplastic polyurethane (B-1: adipate polyurethane), lithium stearate, sodium stearate, Potassium stearate,
Thallium acetate or sodium benzoate was mixed at the ratios shown in Table 1, melt-kneaded using a 30 mm twin-screw extruder at a set temperature of 190 ° C and a screw rotation speed of 80 rpm to form pellets, and the melt tension and melt shear viscosity of the pellets Was measured. In addition, test pieces were prepared using an injection molding machine, and physical properties were evaluated.
For comparison, a polyacetal resin and a thermoplastic polyurethane were used alone or in combination with each other, and further, calcium stearate which does not belong to the component (C) was mixed and evaluated in the same manner as in Examples. Table 1 shows the results. In addition, the measuring method of each characteristic value is as follows. Izod impact strength was performed on notched specimens according to the method of ASTM D256. Melt Tension, Melt Shear Viscosity The melt tension was measured using a Capillograph 1B manufactured by Toyo Seiki Seisaku-Sho, Ltd. at a cylinder temperature of 190 ° C. at a capillary diameter of 1 mmφ, a discharge speed of 0.2 m / min, and a winding speed of 5 m / min. Also, using the same device, shear rate 1.2 × 10 ² s
The shear viscosity was measured at ec ^-1 .

Examples 6 to 9 and Comparative Examples 5 to 6 Tests and evaluations were conducted in the same manner as in the previous example except that the amounts of the thermoplastic polyurethane and lithium stearate were changed. Table 2 shows the results.

Examples 10-11, Comparative Examples 7-8 The types of polyurethane resins in Examples 1 and 3 were changed (B-2: polytetramethylene glycol-based polyurethane, and B-3: adipate-based high viscosity ( 6.4 × 10 ⁴ poise) polyurethane was similarly evaluated. Table 3 shows the results.

Examples 12 to 13 In Example 12, the test and evaluation were carried out in the same manner as in Example 1 except that lithium stearate was melt-kneaded in a polyacetal resin in advance and pelletized once, and the thermoplastic polyurethane was melt-kneaded in the pellet. did. In Example 13, the test and evaluation were conducted in the same manner as in Example 1 except that the polyacetal resin and the polyurethane resin were melt-kneaded in advance, and then lithium stearate was added. Table 4 shows the results.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

[0021]

[Table 4]

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C08L 75:04)

Claims (2)

(57) [Claims] 1. An alkali metal salt of an aliphatic or aromatic carboxylic acid or 100 parts by weight of a resin component comprising 50 to 99 parts by weight of a polyacetal resin (A) and 50 to 1 part by weight of a thermoplastic polyurethane resin (B). A push having improved melt tension, obtained by adding and blending 0.005 to 1 part by weight of thallium salt (C) and melt kneading.
Polyacetal resin composition for blow molding or blow molding . 2. The polyacetal resin composition according to claim 1, wherein the polyacetal resin (A) phase and the thermoplastic polyurethane resin (B) phase are mutually fused.