JP2769287B2 - Molding method of polyacetal resin composition with improved mold deposit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention greatly reduces the amount of mold deposits adhering to the surface of a mold during molding of a polyacetal resin, and enables continuous molding for a long time without impairing the surface properties and dimensional accuracy of the molded product. An object of the present invention is to provide a method for molding a possible polyacetal resin composition.

[0002]

2. Description of the Related Art In recent years, the role of polyacetal as an engineering plastic has been increasing, and it has been used as an important mechanical component in a wide range of fields such as automobiles, electricity, electronics, and miscellaneous goods. There are various processing methods for polyacetal, such as injection molding, extrusion molding, sheet molding, and the like, but the processing method by injection molding is still mainstream. In the injection molding of polyacetal, the surface of the mold is more severe than other resins due to the extension of the continuous molding time, which is a major problem during molding.

[0003] The contaminants adhering to the mold, that is, mold deposits (hereinafter abbreviated as MD) are roughly composed of the following two substances. One is a case where the polyacetal used for molding is contained or formaldehyde generated by decomposition of the main chain of the polyacetal during molding is polymerized on the mold surface and adheres as a polymerizable contaminant (paraform).

[0004] Another is a case where additives added to impart various functions to the polyacetal adhere to the mold surface. This is likely to occur when a highly volatile additive or an additive having low affinity for polyacetal is used, and is remarkable when the additive amount of the additive is large. When MD occurs frequently, not only the quality of the molded product deteriorates, such as a decrease in the dimensional accuracy of the molded product, a deterioration in the surface appearance, a short shot failure due to blockage of the mold gas vent, and an increase in the mold cleaning frequency. Problems such as mold corrosion occur. For polyacetal molding, it has been a long-standing problem to suppress the occurrence of MD, and many studies have been made so far.

Conventionally, the following four types of methods have been studied as a measure against MD during polyacetal molding. (1) Improving the thermal stability of polyacetal and studying a production process with a small amount of unreacted formaldehyde (2) Mild and optimized molding conditions (3) Optimization of mold design (4) Effect of MD remover That is the typical use.

The method (1) aims at suppressing the amount of formaldehyde generated during molding by examining the manufacturing process (Japanese Patent Laid-Open No. 62-119219, etc.). The effective use of additives having the function of trapping in water has been studied. In the method (2), general knowledge is to lower the cylinder temperature of the molding machine and shorten the residence time in order to suppress the decomposition of polyacetal during molding.
Alternatively, optimization has been made in terms of molding conditions, such as lowering the injection speed. Further, it has been considered that the direction in which the water content in the polyacetal decreases due to sufficient predrying of the polyacetal is extremely effective for the purpose of suppressing MD generation (Polyacetal Handbook; edited by Nikkan Kogyo Shimbun).

In the method (3), measures have been taken such as predicting the flow state of the resin in the mold and appropriately setting a gas vent line at a flow end, a weld portion, or the like. Even if the above-mentioned measures (1) to (3) are taken, it is actually difficult to suppress the generation of MD during molding, and as in the method (4), a function of removing MD adhering to the die. Studies have also been made on MD removers (JP-A-59-12807 and the like) with an increased value. Even if all of these measures are taken, polyacetal molding conditions, mold structures, etc., are diversified along with the diversification of polyacetal applications, and measures that can universally suppress MD generation are still established. Not. Suppressing the occurrence of MD still remains as a major issue regarding polyacetal molding.

[0008]

DISCLOSURE OF THE INVENTION The present invention dramatically reduces MD generated during polyacetal molding, suppresses dimensional accuracy and surface property of polyacetal molded products, and reduces the frequency of mold cleaning. It significantly improves mold corrosion resistance and the like.

[0009]

Means for Solving the Problems As a result of intensive studies, the present inventor has found that water and / or a limited alcoholic compound is used when a specific polyacetal resin composition is used and when the composition is molded. It was discovered that the addition of a certain limited amount significantly reduced MD, leading to the present invention.

That is, the present invention relates to (A) 100 parts by weight of a polyoxymethylene copolymer, and (B) 5% by weight of a volatile component when heated at 230 ° C. for 60 minutes in an air stream.
The following hindered phenolic antioxidants 0.05
To 2 parts by weight, (C) at least one oxide selected from alkali metal oxides and alkaline earth metal oxides and 3
An ion adsorbent mainly composed of at least two kinds of oxides composed of at least one kind of oxide selected from valence element oxides,
And the following general formula (1): M _{11 1−X} M _2X (OH) _{2 An} ⁻ _{X / n} · mH ₂ O (1) (wherein M ₁ is at least one kind of 2 selected from alkaline earth metals) M ₂ represents a trivalent metal, and A ^n-
Represents an n-valent anion. X is 0 <x ≦ 0.5, and m is a positive number. At least one ion adsorbent selected from the ion adsorbents represented by
An alcoholic compound having water and / or a hydroxyl group and having a boiling point of 250 ° C. or less is added to 100 parts by weight of the polyacetal resin composition obtained by melt-kneading 0.3 part by weight.
02 to 2.0 parts by weight at the time of molding or immediately before molding ,
The present invention relates to a method for molding a polyacetal resin composition having an improved mold deposit, characterized by performing molding.

The polyoxymethylene copolymer which is the component (A) of the polyacetal resin composition used in the present invention is contained in a chain composed of oxymethylene units obtained by copolymerizing formaldehyde or trioxane with a cyclic ether or cyclic formal. The following general formula (2)

[0012]

Embedded image

A polyoxymethylene copolymer having a structure in which an oxyalkylene unit represented by the following formula is randomly inserted is stabilized by a known method against decomposition from a polymerized terminal. As a method for stabilizing the polymerization terminal,
For example, a method such as esterification, etherification, urethanization of a terminal hydroxyl group, or a method of stabilizing a molecular terminal by hydrolyzing an unstable portion at a polymerization terminal is used.

The polyoxymethylene copolymer includes a branched polyoxymethylene copolymer having a branched molecular chain, and a polyoxymethylene block copolymer with a heterogeneous component block containing at least 50% by weight of an oxymethylene repeating unit. Is also included. The insertion ratio of the oxyalkylene unit in the polyoxymethylene copolymer is in the range of 0.05 to 50 mol, preferably 0.1 to 20 mol, per 100 mol of the oxymethylene unit. Examples of the oxyalkylene unit include an oxyethylene unit, an oxypropylene unit, an oxytetramethylene unit, an oxybutylene unit, and an oxyphenylethylene unit.
From the viewpoint of improving the physical properties of the polyacetal resin composition Among these oxyethylene units, oxyethylene units - [(CH _{2) 2} O], - and oxytetramethylene units - [(CH _{2) 4} O] - especially preferable.

The hindered phenolic antioxidant, which is the component (B) of the polyacetal resin composition used in the present invention, means that the compound has an amount of volatile components when heated at 230 ° C. for 60 minutes in an air stream. 5% by weight or less, and specific examples of the compound preferably used include 1,1
3,5-trimethyl-2,4,6 tris (3,5-di-
t-butyl-4-hydroxybenzyl) benzene, triethylene glycol-bis [3- (3-t-butyl-5
-Methyl-4-hydroxyphenyl) propionate], 3,9-bis [1,1-dimethyl-2- {β-
(3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxydiethyl] -2,4,8,10
Tetraoxaspiro [5.5] undecane, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], N,
N'-hexamethylenebis (3,5-di-t-butyl-
4-hydroxy-hydrocinnamide), 1,6-hexanediol-bis [3- (3,5-di-t-butyl-
4-hydroxyphenyl) propionate], 1,3
5-trimethyl-2,4,6-tris (3,5-di-t
-Butyl-4-hydroxybenzyl) benzene, N,
N'-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyl] hydrazine;
5-tris (4-t-butyl-3-hydroxy-2,6
-Dimethylbenzyl) isocyanuric acid and the like. Of these, triethylene glycol-bis [3-
(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 3,9- Bis [1,1-dimethyl-2 @ β- (3-t-butyl-4-hydroxy-
5-methylphenyl) propionyloxydiethyl]-
2,4,8,10 tetraoxaspiro [5,5] undecane, 1,3,5-tris (4-t-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid and the like.

The hindered phenolic antioxidant which is the component (B) of the polyacetal resin composition used in the present invention may be used alone or in combination of one or more. The amount is 0.05 to 2 parts by weight, preferably 0.1 to 1 part by weight, based on 100 parts by weight of the polyoxymethylene copolymer (A). When the amount is less than 0.05 part by weight, the heat stability of the polyacetal resin composition is lowered, and the object of the present invention cannot be achieved. If the amount exceeds 2 parts by weight, the mold deposit becomes defective.

As one of the ion adsorbents, which is the component (C) of the polyacetal resin composition used in the present invention, at least one oxide selected from alkali metal oxides and alkaline earth metal oxides; There is an ion adsorbent mainly composed of two or more kinds of oxides composed of at least one kind of oxide selected from valence element oxides. Examples of the alkali metal oxide include Na ₂ O and K ₂ O, and examples of the alkaline earth metal oxide include MgO and CaO. Further, as a trivalent element oxide, Al
Examples include ₂ O ₃ , Ga ₂ O ₃ , In ₂ O ₃ , and B ₂ O ₃ , and a preferable example is Al ₂ O ₃ .

At least 2 selected from these oxides
Suitable as an ion adsorbent mainly composed of a kind of oxide
Is “2.5MgO · Al_TwoO_Three・ NH_TwoO ”,“ Al_Two
O_Three・ Na_TwoO ・ nH_TwoO ”,“ Mg_0.7Al_0.3O
_1.15”,“ Mg_0.75Al_0.25O _1.125"
You. Further, as another ion adsorbent used in the present invention
There is an ion adsorbent of the following general (1).

M _{1 1−x} M _2x (OH) _{2 An} ⁻ _{x / n} · mH ₂ O (1) In the above formula (1), M ₁ is at least one divalent selected from alkaline earth metals. A metal is shown, and preferable examples thereof include Mg and Ca. In the above formula (1), M ₂ is a trivalent metal, and B, Al,
Ga, In, Tl, etc. are shown, and a preferable example is Al.

Furthermore, A ^n-is At a the equation (1) shows an n-valent anion such as _{^{CO 3 2-, OH -, HCO}} 3 -,
H ₂ PO ₄ ⁻ , NO ₃ ⁻ , I ⁻ , salicylate ion ⁻ ,
Citrate ^-, tartrate ^-, and the like. CO ₃ ^2- is preferred examples, OH ^- and the like. Specific examples of such ion adsorbents include, for example, Mg
_0.75 Al _0.25 (OH) ₂ (CO ₃ ) _0.125・ 0.5H ₂
Natural hydrotalcite represented by O, Mg _4.5 Al ₂
(OH) ₁₃ CO ₃ .3.5H ₂ O, Mg _6.0 Al ₂ (O
H) There is a synthetic hydrotalcite represented by ₁₆ CO ₃ .4H ₂ O or the like.

The particle size of the ion adsorbent which is the component (C) of the polyacetal resin composition used in the present invention is not particularly limited, but is preferably 100 μm or less in order to improve dispersibility. Also, the ion adsorbent is compatible with the polymer,
In order to improve dispersibility and the like, a surface treatment with a surface treatment agent may be performed. Examples of the surface treatment agent include an organic acid having 2 to 30 carbon atoms and at least one -COOH group and / or an alcohol having 2 to 30 carbon atoms (primary, secondary or tertiary alcohol) and Metal salts and the like composed of the above two and a metal selected from the group consisting of alkali metals, alkaline earth metals and aluminum, such as stearic acid, linoleic acid, oleic acid, lauric acid, sodium stearate, stearin Magnesium acid,
Sodium oleate and the like can be mentioned.

Further, the ion adsorbent according to the present invention comprises:
Decrystallization water treatment may be performed. The decrystallization water treatment can be easily performed, for example, by a method in which the treatment is performed at a temperature of about 110 ° C. to about 400 ° C. for about 1 to 40 hours in air or in an atmosphere of N ₂ , He, O ₂ , CO _2, or the like. . One of the above-mentioned ion adsorbents may be used, or two or more of them may be used in combination.

The compounding amount is from 0.002 to 0. 0 to 100 parts by weight of the polyoxymethylene copolymer (A).
3 parts by weight, preferably 0.005 to 0.1 part by weight. When the amount is less than 0.002 parts by weight, the effect of suppressing mold deposit during molding is not sufficiently exhibited, and when the amount exceeds 0.3 parts by weight, the thermal stability of the polyacetal resin composition is reduced. It is not preferable because it causes a decrease and the generation of mold deposit is promoted.

In the polyacetal resin composition used in the present invention, a commonly used heat stabilizer (formaldehyde scavenger) can be added. Examples of the heat stabilizer include polyamide resins, amide compounds, urea derivatives, triazine derivatives, urethane compounds, and the like.Specifically, condensation of a diamine and a dicarboxylic acid, condensation of an amino acid, lactam ring-opening polymerization, and the like Nylon 6, nylon 11, nylon 12, nylon 6 obtained
6, nylon 6/10, nylon 6/6/10, nylon 6/6/6, nylon 6.6 / 6/10, nylon 6
/ 6/6/6/10 or poly-β-alanine or other polyamide resin, aliphatic monocarboxylic acid, dicarboxylic acid or aromatic monocarboxylic acid, dicarboxylic acid and aliphatic monoamine, diamine, or aromatic monoamine, diamine The resulting stearyl stearamide, stearyl oleamide, stearyl erucamide, ethylenediamine-distearamide, ethylenediamine-dibehenamide, hexamethylenediamine-distearamide, ethylenediamine-dioleamide, ethylenediamine-dierucaramide, Amide compounds such as xylylenediamine-dierucamide, di (xylylenediamine-stearic acid amide) sebacamide, N-phenylurea, N, N'-diphenylurea, N-phenylthiamide Urea, N, urea derivatives such as N'- diphenyl thiourea, melamine, benzoguanamine, N
-Phenylmelamine, melem, N, N'-diphenylmelamine, N-methylolmelamine, N, N'-trimethylolmelamine, 2,4-diamino-6-cyclohexyltriazine, triazine derivatives such as melam and the like.
One of these heat stabilizers may be used alone, or two or more thereof may be used in combination.

The polyacetal resin composition used in the present invention may further contain, if desired, other additives such as a light stabilizer, a lubricant, a release agent, an antistatic agent, an inorganic filler such as glass fiber, carbon dioxide, and the like. Reinforcing agents such as fibers, pigments and the like can be blended as desired. In order not to impair the effects of the present invention, the heat stabilizer and other additives are additives having a low decomposing effect on the polyoxymethylene copolymer, or heat stabilizers or other additives themselves. It is desirable that the thermal stability is high.

In the polyacetal resin composition used in the present invention, the mixing of the component (A) with the above components blended with the polyoxymethylene copolymer is carried out by a commonly used melt mixing method. When used in combination with a heat stabilizer or other additives, they may be melt-mixed at the same time. The added form of each component to be added may be a powder or a molten state.

The most preferred compound that can be used for the polyacetal resin composition of the present invention is water (H ₂ O). As a general method for molding a polyacetal resin, it is known to predry the polyacetal resin before molding. This is because when molding is performed with a trace amount of water remaining in the conventional polyacetal resin,
This is because it has been believed that MD generation is promoted and molding defects are caused.

However, the present inventor has discovered that when water is added to the polyacetal resin composition referred to in the present application to a certain amount of polyacetal and then molding is performed, the generation of MD can be remarkably suppressed. This is a reversal of the conventional perception, and is a phenomenon that cannot be analogized at all by those skilled in the art.
Next, the alcoholic compound referred to in the present invention will be described in detail.

The alcoholic compound that can be used in the present invention needs to have a hydroxyl group and have a boiling point of 250 ° C. or less. By using a compound having a hydroxyl group (-OH group), the self-polymerization property of formaldehyde generated during molding can be suppressed, and the phenomenon of adhering to a mold as paraform can be significantly improved. That is, polyacetator
Water and / or water during or immediately before molding the resin composition.
By adding a rucol compound, water and
// Alcohol compound adheres and occurs during molding
Formaldehyde self-polymerization is suppressed on the mold surface,
MD caused by adhesion to mold as paraform
This is because the occurrence of phenomena can be suppressed.

The number of hydroxyl groups in the alcoholic compound is not particularly limited. The alcoholic compound may have at least one or more hydroxyl groups in the molecule, and the alcoholic compound may have two or more hydroxyl groups. The boiling point of alcoholic compounds is 2
It is necessary that the temperature be 50 ° C. or less. The boiling point in the present invention is a boiling point under normal pressure (760 mmHg).

When the boiling point is higher than 250 ° C., the effect of greatly improving MD referred to in the present invention is not exhibited. This will be evident in later comparative examples. The boiling point of the alcoholic compound is preferably in the range of 70 to 180 ° C.
It is more preferable that the temperature be between -160 ° C. Specific examples of the alcoholic compound that can be used in the present invention include:
For example, methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, sec-butyl alcohol, tert-butyl alcohol, n-amyl alcohol, isoamyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, cabyl alcohol And aliphatic saturated alcohols such as decyl alcohol.

Further, aliphatic unsaturated alcohols such as allyl alcohol, crotyl alcohol and propargyl alcohol, alicyclic alcohols such as cyclopentanol and cyclohexanol, aromatic alcohols such as benzyl alcohol, and heterocycles such as furfuryl alcohol Formula alcohols and the like can also be used in the present invention. Preferred alcoholic compounds can be selected from aliphatic saturated alcohols and alicyclic alcohols. Further, an aliphatic saturated alcohol having 1 to 8 carbon atoms is more preferable.

The amount of water and / or alcoholic compound added must be between 0.02 and 2.0 parts by weight based on 100 parts by weight of the polyacetal resin composition.
The weight of the polyacetal resin composition in the present invention is 14
The weight after drying at 0 ° C. for 3 hours. If the amount of the water and / or alcoholic compound is less than 0.02 parts by weight based on 100 parts by weight of the polyacetal, it is impossible to suppress the generation of MD during molding of the polyacetal resin composition. If the amount of water and / or alcoholic compound added is more than 2.0 parts by weight, molding defects such as a decrease in surface properties and a decrease in dimensional accuracy of the polyacetal molded product occur, and the molding of the desired polyacetal resin composition. Can not get the goods.

Preferably, the amount of the water and / or alcoholic compound is between 0.05 and 1.0 part by weight, more preferably between 0.05 and 0.5 part by weight, per 100 parts by weight of the polyacetal resin composition. It is preferably between parts by weight. A method for adding water and / or an alcoholic compound to the polyacetal resin composition will be described below.

For example, a method of feeding a water and / or alcoholic compound which is liquid at the time of molding a polyacetal resin composition into a molding machine using a quantitative feeder or the like, or a pellet-like or powder-like polyacetal just before molding. There is a method in which water and / or an alcoholic compound is attached to the resin composition, and the mixture is sufficiently blended to form a polyacetal resin composition.

[0036]

These water and / or alcoholic compounds may be used alone or in combination of two or more. The water and / or alcoholic compound used is preferably as small as possible in impurities such as alkali metals, alkaline earth metals, and halogen compounds for the purpose of preventing the thermal stability of the polyacetal resin composition from lowering. The present invention provides a polyacetal resin composition having a synergistic effect with a hindered phenolic antioxidant as a component (B) and an ion adsorbent as a component (C), and a water and / or alcoholic compound during molding. The desired effect of the present invention can be exhibited by the effect of addition, and even if one of the hindered phenolic antioxidant as the component (B) and the ion adsorbent as the component (C) is lacking. The object of the present invention cannot be achieved.

[0038]

Next, the present invention will be described in more detail by way of examples, which should not be construed as limiting the present invention. The properties and evaluation criteria of the compositions in Examples and Comparative Examples are as follows. (1) Amount of volatile components Using a thermal balance manufactured by Rigaku Co., Ltd., a sample was placed in an electric furnace at 50 m.
g and air 5Nl / hr, and 40 to 20 ° C
Temperature per minute. After heating to 230 ° C., the sample was heated for 60 minutes, and the weight loss rate of the sample at that time was measured. The smaller the value, the smaller the amount of volatile components. (2) Thermal stability Gear oven [Tabai Seisakusho, GPS-222]
Mold, exhaust duct 20 ° open] using 140 ° C × 400
A long-term hot air test was conducted. For the evaluation, the tensile elongation (measured by AST
MD-638) and its retention was determined.
The larger this value, the better the thermal stability.

Retention (%) = Tensile elongation of stay molded product / Tensile elongation of initial molded product × 100 (3) Evaluation of mold deposit by continuous molding Injection molding machine Ti-30G manufactured by Toyo Machine Metal Co., Ltd. Pressure 500kg / cm ² Injection speed 100% Cylinder temperature 225 ° C Injection time 6sec Cooling 4sec Mold temperature 30 ° C Zac back 4mm Molded product Length 35mm Width 14mm, Thickness 2mm Mold Pin gate mold Continuous molding under the above conditions After 2000 shots, the state of the mold deposit adhering to the mold was visually observed and evaluated according to the following criteria.

A: No mold deposit is observed. : Almost no mold deposit was observed. C: Mold deposit is slightly recognized. X: Mold deposit is clearly recognized. XX: Mold deposit is thickly attached to the entire surface of the mold.

The symbols in the table indicate the following. Hindered phenol A-1; triethylene glycol-bis [3- (3-t
-Butyl-5-methyl-4-hydroxyphenyl) propionate] A-2; pentaerythrityl-tetrakis [3- (3,
5-di-t-butyl-4-hydroxyphenyl) propionate] A-3; 3,9-bis [1,1-dimethyl-2 @ β-
(3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxydiethyl] -2,4,8,10
Tetraoxaspiro [5,5] undecane A-4; 2,2'-methylenebis (4-methyl-6-t
-Butylphenol) A-5; 2-t-butyl-6- (3'-t-butyl-
5'-methyl-2'-hydroxybenzyl) 4-methylphenyl acrylate A-6; 1,3,5-tris (4-t-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid.

[0042]

Examples 1 to 26, Comparative Examples 1 to 12 Trioxane-ethylene oxide copolymer 100 containing about 2.4% by weight of oxyethylene units derived from ethylene oxytodiene having a melt index of 9.1 g / 10 min. The hindered phenolic antioxidant as the component (B) and the ion adsorbent as the component (C) having the volatile component amounts shown in Tables 1 to 4 in parts by weight are added in the amounts shown in Tables 1 to 4. And mixed homogeneously with a Henschel mixer. Next, this mixture was passed through a 50φ extruder, melt-kneaded, and the obtained strand obtained as a strand from the die head was immediately formed into a pellet, and further dried at 140 ° C. for 3 hours to obtain a polyacetal resin composition. Tables 1 to 4 show the thermal stability of the obtained composition.

Water and alcoholic compounds shown in Tables 1 to 4 were added to the above-mentioned polyacetal resin compositions in the amounts shown in Tables 1 to 4, and continuous molding was performed to evaluate a mold deposit. The results are shown in Tables 1 to 4. Table 1
From the results in Table 4, the following can be understood. 1) Each of the examples has an excellent effect on the amount of mold deposit generated during molding. 2) In Comparative Example 1, the mold deposit was extremely poor because no alcoholic compound was added. 3) In Comparative Example 2, the heat stability of the polyacetal resin composition was lowered because the amount of the hindered phenolic antioxidant added was too small, and mold deposits were generated despite the addition of the alcoholic compound. The amount increased significantly. 4) In Comparative Example 3, the mold deposit was poor because the added amount of the hindered phenolic antioxidant was excessive. 5) In Comparative Example 4, since the amount of the ion adsorbent added was too small, the effect of suppressing the mold deposit was reduced. 6) In Comparative Example 5, the thermal stability of the polyacetal resin composition was lowered due to the excessive amount of the ion adsorbent, and the amount of mold deposits was extremely poor. 7) In Comparative Examples 6 and 7, since the amount of the volatile component of the hindered phenol-based antioxidant was excessive, the amount of mold deposit generated significantly increased. 8) In Comparative Example 8, since an alcoholic compound having a boiling point exceeding 250 ° C. was used, the effect of suppressing mold deposit could not be exhibited. 9) In Comparative Examples 9 and 11, since the amount of the alcoholic compound added was too small, the effect of suppressing mold deposits could not be exhibited, and the amount of mold deposits generated was extremely poor. 10) In Comparative Examples 10 and 12, since the added amount of the alcoholic compound was excessive, the surface property of the molded article was deteriorated, and a foaming state was observed on the surface of the molded article, and at the same time, the effect of suppressing mold deposit could be exhibited. Did not.

[0044]

[Table 1]

[0045]

[Table 2]

[0046]

[Table 3]

[0047]

[Table 4]

[0048]

According to the present invention, as compared with the conventional polyacetal resin, the amount of mold deposit adhering to the mold surface during molding is extremely small, so that continuous molding can be performed without impairing the surface properties and dimensional accuracy of the molded product. It can greatly contribute to productivity improvement.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ identification code FI C08K 5:13) (58) Investigated field (Int.Cl. ⁶ , DB name) C08L 59/00-59/04 C08J 5 / 00-5/24 C08G 2/00-2/38

Claims (5)

(57) [Claims] 1. A polyoxymethylene copolymer (A)
0 parts by weight, (B) 0.05 to 2 parts by weight of a hindered phenolic antioxidant having a volatile component content of 5% by weight or less when heated at 230 ° C. for 60 minutes in an air stream, (C) alkali An ion mainly composed of at least one oxide selected from metal oxides and alkaline earth metal oxides and at least two oxides selected from at least one oxide selected from trivalent element oxides Adsorbent, and the following general formula (1): M _{1 1−X} M _2X (OH) _{2 An} ⁻ _{X / n} · mH ₂ O (1) (where M ₁ is at least one selected from alkaline earth metals) M ₂ represents a trivalent metal, and A ^n-
Represents an n-valent anion. X is 0 <x ≦ 0.5, and m is a positive number. ) At least one type of ion adsorbent selected from the ion adsorbents represented by
An alcoholic compound having water and / or a hydroxyl group and having a boiling point of 250 ° C. or lower is added to 100 parts by weight of the polyacetal resin composition obtained by melt-kneading 3 parts by weight. 02 ~
2. A method for molding a polyacetal resin composition having an improved mold deposit, wherein 2.0 parts by weight are added at the time of molding or immediately before molding to carry out molding. 2. The hindered phenolic antioxidant comprises triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], pentaerythrityl-tetrakis [3- (3,5
-Di-t-butyl-4-hydroxyphenyl) propionate], 3,9-bis [1,1-dimethyl-2 @ β-
(3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxydiethyl] -2,4,8,10
Tetraoxaspiro [5,5] undecane, 1,3,5
-Tris (4-tert-butyl-3-hydroxy-2,6-
2. The method for molding a polyacetal resin composition according to claim 1, wherein the composition is dimethylbenzyl) isocyanuric acid. 3. The method according to claim 1, wherein the ion adsorbent is Mg _0.75 Al _0.25
O _1.125 , Mg _0.7 Al _0.3 O _1.15 , Mg _0.75 Al _0.25
(OH) ₂ (CO ₃ ) _0.125 · 0.5H ₂ O, 2.5M
gO.Al ₂ O ₃ .nH ₂ O, Al ₂ O ₃ .Na ₂ O.
nH ₂ OMg _4.5 Al ₂ (OH) ₁₃ CO ₃ .3.5H ₂
The method of molding a polyacetal resin composition according to claim 1, wherein O and Molding according to claim 4, wherein the alcoholic compound is an aliphatic saturated alcohols, the polyacetal resin composition of claim 1 wherein the alicyclic alcohol. 5. The method for molding a polyacetal resin composition according to claim 1, wherein the amount of said water and / or alcoholic compound is 0.05 to 0.5 parts by weight based on 100 parts by weight of the polyacetal resin composition. .