JPH0812734A - Blow-molding polyacetal copolymer resin, blow-molding hollow-molded article and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Purpose] A blow that combines melt tension and fluidity, which are important for blow molding, and has excellent blow moldability, with little deterioration in quality due to decomposition etc. in the compound and blow molding processes, and a good appearance. Provided is a blow molding polyacetal resin which is capable of stably obtaining a molded product, particularly a large blow molded product, and which is also suitable for recycling. [Structure] An oxymethylene group as a main repeating unit,
An oxyalkylene group (having 2 to 4 carbon atoms in the alkylene group)
It is composed of a polyacetal copolymer having a branched or crosslinked structure having a main chain of polyoxymethylene copolymer containing 0.2 to 10% by weight and 0.01 to 0.2% by weight of a glycidyl ether residue as a branched or crosslinked portion. Molecular weight is 1
× 10 in ⁵ to 3 × 10 ^5, and the molecular weight 1 × 10 ⁶ or more high molecular weight component contains 1 to 10 wt%, the shear viscosity of 1.0 ×
Polyacetal copolymer resin for blow molding with 10 ³ to 3.5 × 10 ³ Pa · s (190 ° C., shear rate 120 sec ⁻¹ ).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blow molding polyacetal copolymer resin, a blow molding method thereof, and a hollow molded article produced by blow molding.

[0002]

2. Description of the Related Art Polyacetal resins have a good balance of mechanical properties, chemical resistance, slidability, etc., and are easy to process. It is widely used as electric / electronic parts, automobile parts and various other mechanical parts, but most of them are injection molded parts. on the other hand,
In recent years, the chemical resistance of polyacetal resins, particularly excellent resistance to organic solvents, has been expected to be applied to hollow parts related to automobile fuel tanks or engine rooms. The blow molding method is generally used as an efficient means for manufacturing such hollow molded parts, and in order to enable blow molding, it is possible to prevent breakage and uneven thickness of the molded product due to drawdown of the parison during molding. Therefore, it is generally necessary to increase the melt tension of the resin. In order to raise the melt tension, it is generally considered effective to increase the molecular weight of the resin.For example, in general-purpose resins such as high-density polyethylene and polypropylene resin used for blow molding, the average molecular weight of ultra-high molecular weight type of several hundred thousand or more Things are widely used. Polyacetal resins are also relatively low molecular weights and low viscosities for general molding resins and are suitable for injection molding and the like, but they are impossible for blow molding because drawdown of parison occurs. Therefore, there are some attempts to improve the blow moldability by devising the polymerization method etc. to increase the molecular weight (including branching, crosslinking, etc.), but the sufficiently high molecular weight polyacetal resin is markedly poor in fluidity. Therefore, blow molding is still difficult even if the drawdown property is improved, and when such high molecular weight and high viscosity polyacetal is subjected to the compound process and blow molding process, it locally generates heat due to melt shearing and the molecular weight due to decomposition It is extremely difficult to obtain a sufficiently satisfactory molded product due to adverse effects such as deterioration and foaming. Also, heat generated by melt shearing,
In order to avoid abnormal temperature rise, the rotation of screws, paddles, etc. is reduced and the shearing speed is reduced by means such as insufficient prevention of quality deterioration and molecular weight decrease, and stable production is difficult, and industrial Mass production is difficult and costly, which is not preferable. On the other hand, a polyacetal resin having a branched or crosslinked structure tends to have a low viscosity in a high shear state for its high molecular weight, but if a branched or crosslinked structure is simply formed, the melt tension and the flow characteristics are harmonized. Even if blow molding is possible, even if blow molding is possible, it is difficult to adjust the molding conditions and the molding efficiency is poor, and the smoothness of the surface of the molded product is not obtained, and spot-like unevenness is likely to occur and the appearance of the molded product, etc. The fact is that the drawbacks of quality are unavoidable. Further, in blow molding, it is generally required for economic reasons to grind unnecessary parts other than the molded body such as runners and sprues generated at the time of molding and finished molded bodies, and to reuse them for molding again. Another problem with blow molding of polyacetal resin is that the melt tension of the resin during such recycle is markedly reduced and the reuse is impeded.

[0003]

In view of such circumstances, the present inventors have excellent blow moldability by combining melt tension and fluidity, which are important for blow molding, and have a quality due to decomposition or the like in a compound process or blow molding process. As a result of earnest research on a blow molding polyacetal resin which is suitable for recycling, it is possible to obtain a blow molded product having a good appearance with a small decrease, particularly a large blow molded product, and it has a specific molecular structure. The inventors have found that the above problems can be solved by blow molding using a polyacetal copolymer resin having a specific molecular weight and molecular weight distribution, and have completed the present invention. That is, the present invention has a polyoxymethylene copolymer having an oxymethylene group as a main repeating unit and containing 0.2 to 10% by weight of an oxyalkylene group (the number of carbon atoms of the alkylene group is 2 to 4) as a main chain, and branched or crosslinked. A branched or crosslinked polyacetal copolymer having 0.01 to 0.2% by weight of a glycidyl ether residue as a part,
It has a weight average molecular weight of 1 × 10 ^{5 to} 3 × 10 ⁵ , and contains 1 to 10% by weight of a high molecular weight component having a molecular weight of 1 × 10 ⁶ or more, and its shear viscosity is 1.0 × 10 ³ to 3.5 × 10 ^3. Pa ・ s (190
C., a shear rate of 120 sec ^-1 ) blow molding polyacetal copolymer resin, and a method for producing a hollow molded article, characterized by blow molding, using such a polyacetal copolymer resin or a composition mainly comprising this And hollow molded articles molded by the manufacturing method. That is, the feature of the present invention is as a polyacetal resin used for blow molding,
As described above, the main chain is a polyoxymethylene copolymer containing an oxymethylene group as a main repeating unit and an oxyalkylene group (having 2 to 4 carbon atoms in the alkylene group) as a copolymerized unit in an amount of 0.2 to 10% by weight, and having a branched structure. Or a polyacetal copolymer having a branched or crosslinked structure having 0.01 to 0.2% by weight of a glycidyl ether residue as a crosslinking part, and the weight average molecular weight thereof is in the range of 1 × 10 ^{5 to} 3 × 10 ⁵ .
In addition, it contains 1 to 10% by weight of a high molecular weight component having a molecular weight of 1 × 10 ⁶ or more as its molecular weight distribution, and its shear viscosity is 1.0 ×.
The point is to use a polyacetal copolymer resin satisfying 10 ³ to 3.5 × 10 ³ Pa · s (190 ° C., shear rate 120 sec ⁻¹ ).

The respective requirements for constituting the blow molding polyacetal copolymer resin of the present invention will be described below. First, the copolymerization unit constituting a part of the main chain of the polyacetal resin of the present invention is composed of an oxyalkylene group having 2 to 4 carbon atoms, and the amount thereof is 0.2 to 10% by weight, preferably 0.3 to 8% based on the copolymer. % By weight. This component is a proton NM of a solution containing hexafluoroisopropanol-d ₂ as a solvent.
It can be quantified from the R measurement (for details, see Examples below), and can be easily adjusted by the amount of the comonomer used during the polymerization as described later. If this amount is too small, it lacks thermal stability and cannot be applied to blow molding. On the other hand, if it is too large, a predetermined average degree of polymerization and its distribution cannot be obtained, and the melt tension is remarkably lowered, which causes drawdown to make blow molding impossible.

Next, the amount of the glycidyl ether residue constituting the branched or frame structure is 0.01 to 0.2% by weight, preferably 0.02 to 0.15% by weight. This can be quantified by thermally decomposing the polyacetal resin with a hydrochloric acid-methanol mixed solution, purifying the decomposed solution, and performing proton NMR measurement (for details, refer to Examples described later). If this amount is too small, it means that the degree of branching or crosslinking is too small,
Predetermined appropriate average molecular weight and molecular weight distribution cannot be obtained, and melt tension and fluidity cannot be compatible. On the other hand, if it is too large, the melt tension will increase, but the fluidity will deteriorate, and if it is remarkable, it will gel and the flow will be difficult, making blow molding impossible. That is, when the amount of the glycidyl ether residue forming the branched or crosslinked portion is out of the above range, the melt tension (drawdown property) important for blow moldability and the fluidity cannot be obtained, which is not preferable. Therefore, the amount of the glycidyl ether residue forming the branched or framed portion is an important requirement in the present invention, but this is not a sufficient requirement alone, and it is necessary to combine the requirements described later.

That is, in the present invention, the weight average molecular weight is further in the range of 1 × 10 ^{5 to} 3 × 10 ⁵ , and the molecular weight distribution has a molecular weight of 1 × 10 ⁶ or more in the high molecular weight portion of 1 to 10.
The weight average molecular weight is preferably 1.5 × 10 ⁵ to 2.8 × 10 ⁵ , and 1 × 10 ^{6 to} 5 is preferable.
The high molecular weight portion of × 10 ⁶ is 1 to 10% by weight, and 5 × 10 ⁶
It is desirable that the above ultra high molecular weight part is substantially not included. Here, the weight average molecular weight is hexafluoroisopropanol containing sodium trifluoroacetate as a solvent and a carrier, the polymer solution is subjected to gel permeation chromatography (GPC), and the refractive index (RI) and light scattering (LS) are used in combination. It is a value calculated by polystyrene conversion by a conventional method. Further, the specific high molecular weight (1 × 10 ⁶ or more) component is a value determined by calculating the area ratio of a portion having a specific high molecular weight or more in the RI chromatogram (distribution curve) (details will be described later. See example). The weight average molecular weight and its molecular weight distribution, together with the degree of branching or crosslinking, are important requirements for melt tension and fluidity.If the average molecular weight is too small, melt tension cannot be obtained, and if it is too large, flow It is not preferable because it causes poor quality. As for the molecular weight distribution, the melt tension cannot be satisfactorily obtained even when the high molecular weight part of 1 × 10 ⁶ or more is too small, and when it is too large, the fluidity is insufficient and the surface condition of the molded product deteriorates. Furthermore, the presence of 5 × 10 ⁶ or more ultra-high molecular weight portion is not preferable because uneven unevenness (spots, etc.) occurs in the molded product.

Next, in the present invention, the shear viscosity is 1.0 × 10 ^{3 to} 3.5 × 10 ³ Pa · s (19
0 ℃, shear rate 120 sec ^-1 ), especially 1.5 × 10 ³ to 3.2 × 10 ³
Pa · s is preferable. The shear viscosity was measured using a capillary rheometer using the orifice D / L =
It is a value measured at 190 ° C. and a shear rate of 120 sec ⁻¹ at 1/10 (D = 1 mm). If the shear viscosity is too high, the flowability will be poor and the blow moldability will be poor. If the molding efficiency is poor and molding will be marked, molding will be impossible. On the other hand, if it is too low, the melt tension lowers, the drawdown of the parison is likely to occur, and blow molding becomes difficult or impossible. The value of the shear viscosity is influenced by the amount of the above-mentioned copolymerization component, the degree of branching or crosslinking, the weight average molecular weight and the distribution thereof, etc., but it is not always sufficient that those conditions satisfy the above range. Instead, it is necessary to appropriately adjust within that range and satisfy the above range.

The polyacetal copolymer resin for blow molding of the present invention satisfies all of the above-mentioned respective constitutional requirements, so that the melt tension which is most important for blow moldability and the satisfactory balance of fluidity can be obtained, and particularly good blow molding is achieved. And a blow-molded product can be obtained, whichever condition is not sufficient. The melt tension is preferably 5 to 14 g (temperature 190 ° C., extrusion speed 10 mm / min, take-up speed 10 m / min), particularly preferably 7 to 12 g. If the melt tension is too high, the blow resistance during blow molding becomes excessive and the formability deteriorates. If it is too low, drawdown occurs and blow molding becomes difficult or impossible. The melt tension was measured using a capillary rheometer, and the orifice D / L = 1.
It is a value obtained by measuring the load (tension) at the extrusion speed and the take-up speed at / 10 (D = 1 mm) by a load cell.

The polyacetal resin having such characteristics as the molecular structure is difficult to obtain by a generally known method, and it does not exist as a commercial product at present, but the research by the present inventors made it possible to produce it. That is, the polyacetal resin used in the present invention, trioxane as a main monomer, and a cyclic ether or cyclic formal as a comonomer, and further mixed with a specific compound capable of forming a branched structure, boron trifluoride or its coordination. When copolymerizing in the presence of a catalyst composed of a compound, the polymerization conditions and post-treatment conditions are selected and controlled as follows.

First, as comonomers, ethylene oxide, propylene oxide, 1,3-dioxolane, 1,4-
Examples thereof include butanediol formal, diethylene glycol formal, trioxepane and the like. Among them, ethylene oxide, 1,3-dioxolane, 1,4-butanediol formal and diethylene glycol formal are preferable. The content of oxyalkylene (C2-4) copolymerized units constituting the main chain is related to the amount of these comonomers used, and is not necessarily uniquely determined by the type of comonomer, the polymerization rate, etc. Controlled by quantity. Generally, for trioxane, 0.2 to
It is 12% by weight, particularly preferably 0.3 to 10% by weight.

Next, as a component capable of forming a branched structure,
A glycidyl ether compound having at least 1 to 2 epoxy rings in one molecule is used. When one glycidyl ether group is contained in one molecule, a branched molecular structure is obtained, and in this case, a relatively long chain glycidyl ether (for example, having C ₈ or more) is preferable. In the case of a compound having two glycidyl groups, it is a polymer in which a branched type and a crosslinked type (mainly a crosslinked type) are mixed. The present invention may be any of them,
Particularly, diglycidyl ether having two glycidyl groups is preferable. 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, polybutylene glycol diglycidyl ether and the like can be mentioned, among which ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether,
1,4-butanediol diglycidyl ether and hexamethylene glycol diglycidyl ether are preferred. When the amount of these glycidyl ether compounds used increases, the amount of the branched or crosslinked portion formed tends to increase, but the formation of the branched or crosslinked portion introduced into the polymer is uniquely determined by the amount used. It depends on the type (structure) and reactivity of the glycidyl ether used, as well as other conditions (catalyst, comonomer, polymerization temperature, etc., and secondary effects, so these conditions should be considered. It is generally within the range of 0.01 to 0.2% relative to trioxane.In general, when these branching or crosslinking components increase, the weight average molecular weight increases and the high molecular weight part also tends to increase. There is.

Next, in order to satisfy the requirements of the present invention, it is preferable to appropriately use a molecular weight modifier in combination. As such a molecular weight modifier, a chain transfer agent that does not form an unstable terminal, that is, a low molecular weight linear acetal having both ends with an alkoxy group is preferable, together with the amount of the glycidyl ether compound, a desired weight average molecular weight. And play an important role in controlling the molecular weight distribution. Here, methylal is particularly preferable as the low molecular weight linear acetal, and the amount thereof is 0.001 to 0.
It is 05% by weight. Almost all of this component contributes to the regulation of the molecular weight by forming a terminal group of the polymer by a chain transfer reaction, and as described above, it is determined in relation to the amount of the glycidyl ether compound used, both of which are the average molecular weight and its distribution, Furthermore, it is an important factor in adjusting the shear viscosity.

The amount of the catalyst composed of boron trifluoride or its coordination compound used in the next polymerization reaction should be in the range of 5 × 10 ^-4 to 1 × 10 ^-2 mol% based on the total amount of the monomers. It is particularly preferably 1 × 10 ^{−3 to} 7 × 10 ⁻³ mol%. The amount of the catalyst affects the relative balance of the introduction rate of comonomer, the formation rate of the branched / crosslinked portion, etc. with respect to the progress of polymerization, and is an important factor in obtaining a polymer satisfying the requirements of the present invention. Further, an increase in the amount of the catalyst makes it difficult to properly control the polymerization temperature, and the decomposition reaction during the polymerization becomes dominant to contribute to the decrease of the molecular weight. Not only the deterioration but also the molecular weight distribution is disturbed, and it becomes difficult to maintain the requirements of the present invention. On the other hand, when the amount of the catalyst is too small, the polymerization reaction rate decreases, and the polymerization yield decreases, which is not preferable.

Next, the total amount of active impurities that form unstable terminals in the polymerization system is also important. This is preferably 2 × 10 ^-2 mol% or less with respect to all monomers in order to make the product have a high molecular weight, particularly to contain an appropriate amount of a high molecular weight component having a molecular weight of 1 × 10 ⁶ or more. Examples of these components include water, alcohol (for example, methanol), acid (for example, formic acid) and the like. In particular, the total amount of these active impurities should be 1 x 10
It is preferably ^-2 mol% or less.

As the polymerization method, any conventionally known method can be used, but a continuous bulk polymerization method is generally industrially used to obtain a polymer in the form of a solid powder with the progress of the polymerization using a liquid monomer. preferable. Further, it is desirable that the polymerization temperature of these is maintained at 60 to 105 ° C, especially 65 to 100 ° C.

Further, the catalyst is deactivated after the polymerization by adding the reaction product discharged from the polymerization machine after the polymerization reaction to an aqueous solution containing a basic compound. Here, in order to maintain an appropriate molecular weight as the polyacetal resin used in the present invention, and particularly to retain an appropriate amount of a high molecular weight component having a molecular weight of 1 × 10 ⁶ or more, the crude polymer obtained by the polymerization reaction is rapidly refined to be a deactivator. It is necessary to promote contact with the catalyst to deactivate the catalyst. For example, at least 80% by weight of the crude polymer, preferably 90% by weight or more, is 1.5 mm or less, and 15% by weight or more, preferably 20% by weight or more is 0.3. It is preferable that the fine particles have a size of mm or less. Examples of the basic compound for neutralizing and deactivating the polymerization catalyst include ammonia, amines such as triethylamine, tributylamine, triethanolamine, tributanolamine, alkali metal oxides, alkaline earth metal oxides, and water. Oxides, salts, and other known catalyst deactivators are used. 0.001 ~
It is preferably added as an aqueous solution of 0.5% by weight, particularly 0.02 to 0.3% by weight. The preferred temperature is 10 to 80 ° C, particularly preferably 15 to 60 ° C. Further, it is preferable that after the polymer is discharged, the product is rapidly added to these aqueous solutions for deactivation. The crude polyacetal resin prepared by the polymerization method and the deactivation method is further washed, separated and recovered from unreacted monomers, and dried.

The crude polyacetal resin obtained by the above polymerization is subjected to stabilization treatment by a known method such as decomposition and removal of unstable terminal portions or sealing of unstable terminals with a stable substance, and further various necessary stabilizers. It is compounded and subjected to blow molding. As the stabilizer used here, a conventionally known stabilizer can be used. For example, a hindered phenol compound as an antioxidant and a nitrogen-containing compound as another auxiliary stabilizer, an alkali or alkaline earth metal One or two of oxides, hydroxides, inorganic salts, carboxylates, etc.
Combinations with more than one species can be mentioned.

The polymerization reaction conditions and post-treatment conditions for satisfying the constitutional requirements required for the blow molding polyacetal resin of the present invention have been described above, but the important point is that the polyacetal resin used is the above. The above requirement is not to be bound by the above description.

The polyacetal resin for blow molding according to the present invention may optionally contain general additives such as colorants such as dyes and pigments, lubricants, nucleating agents, and release agents, as long as the object of the present invention is not impaired. , An antistatic agent, a surfactant, etc. may be used alone or in combination of two or more, and other thermoplastic resin, or an inorganic or organic fibrous, powdery or plate-like filler may be used. It can also be used as an auxiliary compounded composition.

In the present invention, when a hollow molded article is manufactured by blow molding using the above polyacetal resin, a molding machine used for blow molding of a general thermoplastic resin is used according to a conventionally known method. I'll do it.
That is, pellets made of the above polyacetal resin or a composition thereof are plasticized by an extruder, and then extruded by an annular die, or injected to form an annular melted or softened parison, which is sandwiched in a mold. Then, a gas is blown into it to expand it, cool it and solidify it, and it is molded as a hollow body. In particular, it is suitable for manufacturing large-sized molded products. Molding conditions include cylinder temperature and die temperature 185 to 230 ℃
Is preferably carried out at 190 to 220 ° C. The mold temperature is preferably 40 to 90 ° C, particularly preferably 50 to 85 ° C. The gas blown into the inside may be air, nitrogen or the like, but air is usually used for economic reasons, and the blowing pressure is preferably 3 to 10 kg / cm ² . Further, it is also possible to use a special molding machine such as a three-dimensional blow molding machine, and to make the polyacetal resin of the present invention or its composition into two or more layers, or to use other materials such as polyolefin, polyester and polyamide resin. It is also possible to perform multilayer blow molding in combination with layers.

[0021]

EFFECT OF THE INVENTION The polyacetal resin or the composition thereof of the present invention has both the melt tension and the fluidity, which are most important for blow molding, and has no trouble such as drawdown of the parison.
It is possible to efficiently and stably perform blow molding, and it is also possible to stably obtain blow molded products with good appearance, shape (uneven thickness, deformation) and physical properties, especially large blow molding.
It is suitable for recycling with little deterioration in quality in the blow molding process. Further, the blow-molded product of the present invention has good mechanical properties and chemical resistance, and is suitable for hollow parts such as automobile fuel tanks and engine room related parts, containers, piping materials such as pipes, and other various industrial applications. Can be widely used.

[0022]

EXAMPLES The present invention will be specifically described below, but the present invention is not limited to these examples. Reference Example 1-Preparation of Polyacetal Resin A1 A continuous mixing reactor composed of a barrel having a jacket through which a heat (cold) medium is passed on the outside and a cross-section in which two circles partially overlap, and a rotary shaft with a paddle. , While rotating the two rotating shafts with paddles at 100 rpm,
Trioxane containing 3.3% by weight of 1,3-dioxolane as a comonomer, 0.07% by weight of 1,4-butanediol diglycidyl ether as a branching component, and 0.03% by weight of methylal as a molecular weight regulator was continuously supplied to one end thereof. At the same time, 1% cyclohexane solution of dibutyl ether coordination compound of boron trifluoride as a catalyst was continuously added to 3 × 10 ⁻³ mol% of all monomers to carry out copolymerization ( 80 ° C water is used for the jacket). As a result of the analysis, the active impurities in all monomers used in this preparation include water 4 × 10 ^-3 mol%, methanol 1 × 10 ^-3 mol%, formic acid 1 × 10 ^-3 mol%, a total of 6 × 10 ^- It was ³ mol%.
The reaction product discharged from the outlet of the polymerizer was quickly passed through a crusher, to which was added an aqueous solution of triethylamine 0.1% at 40 ° C., and the mixture was pulverized into fine particles and simultaneously cooled to deactivate the catalyst. Further, after that, separation, washing and drying were carried out to obtain a crude polyacetal copolymer resin. Next, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-
4-hydroxyphenyl) propionate] (Irganox
1010, manufactured by Ciba Geigy) 0.3 parts by weight and melamine 0.
Add 15 parts by weight and in a twin-screw extruder with a vent, 2
Melt-kneading was performed at 05 ° C to remove unstable portions and simultaneously obtain a pelletized polyacetal resin. The polyacetal copolymer was analyzed by the following method, and as a result, had 2.7% by weight of oxyethylene groups and had a branched and crosslinked portion.
Residue of 1,4-butanediol diglycidyl ether 0.08
%, The terminal methylal residue was 0.04% by weight. The weight average molecular weight is 2.1 × 10 ⁵ , and the molecular weight is 1 × 10 ^6.
The above high molecular weight part was 3.5% by weight, and no ultra high molecular weight part having a molecular weight of 5 × 10 ⁶ or more was observed. The shear viscosity is 2.4.
It was x 10 ³ Pa · s (190 ° C, shear rate 120 sec ^-1 ) and the melt tension was 9.8 (g).

The method of measuring the above characteristic values is as follows. [Measurement of oxyethylene residue and methylal terminal group] The polyacetal copolymer was dissolved in hexafluoroisopropanol-d ₂ and measured by proton NMR (measurement temperature 45 ° C). [Quantification of diglycidyl ether residue (branched and crosslinked portion)] Polyacetal copolymer was decomposed by heating in a hydrochloric acid-methanol mixture solution, the decomposed solution was neutralized, and after separation and purification, chloroform-d ₁ was used as a solvent. Proton NMR measurement (measurement temperature 25 ° C.) was performed. In addition, acetic acid was used as a standard agent for the quantification, and the quantification was calculated as diglycidyl ether. [Weight Average Molecular Weight and Molecular Weight Distribution] The weight average molecular weight and molecular weight distribution were measured by refractive index (RI) and light scattering (LS) using gel permeation chromatography (GPC) manufactured by TOSO, and calculated in terms of polystyrene. The solvent and carrier were hexafluoroisopropanol containing sodium trifluoroacetate, oven temperature 40 ° C, solution concentration 0.1 wt%,
It was measured at a carrier flow rate of 0.2 ml / min. The high molecular weight component (1 × 10 ⁶ or more) was calculated by the area ratio of the specific polymer portion or more in the RI chromatogram (distribution curve). [Shear viscosity] Using a capillary type rheometer manufactured by Toyo Seiki, using a D / L = 1/10 (D = 1 mm) orifice, a value at a temperature of 190 ° C. and a shear rate of 120 sec ⁻¹ was determined. [Melt tension] Using a capillary rheometer manufactured by Toyo Seiki (orifice D / L = 1/10, D = 1 mm), load at a temperature of 190 ° C., extrusion speed of 10 mm / min, take-up speed of 10 m / min (tension ) Was measured by the load cell.

Reference Examples 2-3, Comparative Reference Examples 1-3 Polyacetal resin A2-3, polyacetal resin B
Preparation of 1 to 3 Polymerization and deactivation in the same manner as in Reference Example 1 (Production of A1) except that the concentration of 1,4-butanediol diglycidyl ether was changed.
Then, stabilization treatment was performed to obtain a polyacetal resin, and the characteristic values were measured in the same manner. The results are also shown in Table 1. Reference Examples 4 to 5, Comparative Reference Examples 4 to 6 Polyacetal resin A4 to 5, polyacetal resin B
Preparation of 4 to 6 Reference example 1 except that the catalyst concentration, the active impurity concentration, the methylal concentration, the particle diameter of the crude polyacetal resin particles, etc. were changed.
Polymerization, deactivation, and stabilization treatment were performed in the same manner as in (Production of A1) to obtain a polyacetal resin. The characteristic values are also shown in Table 1. Reference Examples 6 to 7 Preparation of Polyacetal Resins A6 to 7 Except that propylene glycol diglycidyl ether (A6) or hexamethylene glycol diglycidyl ether (A7) was used instead of 1,4-butanediol diglycidyl ether. Polymerization, deactivation, and stabilization were performed in the same manner as in Reference Example 1 (Production of A1) to obtain a polyacetal resin. The characteristic values are shown in Table 1.

[0025]

[Table 1]

* 1, (* 1 '): 1,4-butanediol diglycidyl ether (residue) * 2, (* 2'): Propylene glycol diglycidyl ether (residue) * 3, (* 3 ' ): Hexamethylene glycol diglycidyl ether (residue) Examples 1-7, Comparative Examples 1-6 Polyacetal resin A1-7, polyacetal resin B1
~ 6 using a blow molding machine, cylinder temperature 200 ℃,
Die temperature 200 ℃, mold temperature 70 ℃, blowing pressure 5kg / c
80 × 120 under conditions of m ² , die diameter of 50 mm, and die width of 5 mm
A box type hollow container of × 240 (mm ³ ) was molded, and the moldability of the molded product (the tendency of drawdown of the parison and breakage), the uniformity of the wall thickness of the molded product, the presence or absence of foaming, the appearance, etc. were evaluated. Table 2 shows the results.

The evaluation method is as follows. [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. "Large" Moreover, what the parison cut and dropped due to its own weight was designated as "DD". [Tearing during Blow] It was measured by visually observing whether or not the material was torn during molding. [Molded product thickness uniformity] Cut the molded product,
The thickness of the central portion and the lower portion was measured with a micrometer, and the variation in thickness (% of difference between the maximum value and the minimum value with respect to the average wall thickness) was examined. [Appearance] Visually surface smoothness (gloss uniformity, roughness,
The spots, etc.) were observed.

[0028]

[Table 2]

* 1 A defective shape (mold transfer failure) occurred in the molded product * 2 Unmeasurable Example 8-9, Comparative Examples 7-8 Blow-molded in Examples 1, 2 and 2 and 3, After the polyacetal resin A1, A2, B2, B3 molded product was finely crushed by a crusher and mixed with the original polyacetal resin A1, A2, B2, B3 so that the recycled amount was 50% by weight. The melt tension was measured, and blow molding was performed again under the same conditions as in Example 1 to evaluate the moldability of the molded product, the uniformity of the wall thickness of the molded product, and the like. The results are shown in Table 3.

[0030]

[Table 3]

* 1 Cannot measure

Claims (5)

[Claims] 1. An oxymethylene group as a main repeating unit, and an oxyalkylene group (having 2 to 2 carbon atoms in the alkylene group).
4) a polyoxymethylene copolymer containing 0.2 to 10% by weight as a main chain, and a branched or crosslinked polyacetal copolymer having 0.01 to 0.2% by weight of a glycidyl ether residue as a branched or crosslinked portion, It has a weight average molecular weight of 1 × 10 ^{5 to} 3 × 10 ⁵ , and contains 1 to 10% by weight of a high molecular weight component having a molecular weight of 1 × 10 ⁶ or more.
1.0 × 10 ³ to 3.5 × 10 ³ Pa ・ s (190 ° C, shear rate 120 sec
^-1 ) is a blow molding polyacetal copolymer resin. 2. The polyacetal copolymer resin for blow molding according to claim 1, wherein the glycidyl ether residue in the branched or crosslinked portion is formed of diglycidyl ether. 3. The blow molding polyacetal copolymer resin according to claim 1, which has a melt tension of 5 to 14 g (temperature 190 ° C., extrusion speed 10 mm / min, take-up speed 10 m / min). 4. A method for producing a hollow molded article, which comprises blow molding using the polyacetal copolymer resin according to any one of claims 1 to 3 or a composition containing the polyacetal copolymer resin as a main component. 5. A hollow molded article molded by the manufacturing method according to claim 4.