JP2001354833A - Polyacetal resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin material improved in electroconductive stability while maintaining various kinds of excellent characteristics such as appearance or rigidity possessed by a polyacetal resin. SOLUTION: This polyacetal resin composition is obtained by compounding (A) 100 pts.wt. of a polyacetal copolymer prepared by copolymerizing (a) 100 pts.wt. of trioxane with (b) 0.0005-2 pts.wt. of a compound having >=2 cyclic ether units in one molecule and (c) 0-20 pts.wt. of a compound having one cyclic ether unit in one molecule and having 15-150 mmol/kg content of whole terminal groups with (B) 0.1-30 pts.wt. of one or more kinds of electroconductive carbonaceous substances selected from carbon black and carbon fibers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a polyacetal resin composition having excellent conductivity stability. More specifically,
The present invention relates to a polyacetal resin composition having stable conductivity even when the extrusion / molding conditions are changed.

[0002]

2. Description of the Related Art Polyacetal resins have excellent properties in mechanical properties, thermal properties, electrical properties, slidability, moldability, and the like. Widely used for parts, precision machine parts, etc. However, with the expansion of the field in which polyacetal resins are used, the required characteristics tend to be increasingly sophisticated, complex, and specialized. As such required characteristics, further improvement in conductivity stability is demanded. In other words, it is very important to stably obtain desired predetermined conductive characteristics, regardless of the degree of conductivity.

In general, as a method for imparting conductivity to a polyacetal resin, it is known to blend a conductive carbon-based substance such as carbon black or carbon fiber. For example, JP-A-59-51937 and JP-A-62-2
JP-A-67351 and JP-A-6-212052 disclose a composition in which a carbon-based substance such as carbon black or carbon fiber is blended, and further a specific compound for improving thermal stability or the like is blended. . However, when such a carbon-based material is blended with a general linear polyacetal resin, the conductive properties of the resulting composition or a molded article obtained by molding the same are affected by the processing during preparation of the composition or molding of the molded article. It is easily affected by conditions such as kneading conditions such as a cylinder temperature of an extruder or a molding machine and a screw rotation speed, and it is difficult to stably obtain a predetermined conductivity.
This is presumed to be due to the dispersed state of the compounded carbon-based material.

[0004] As a method for improving this and obtaining a stable and reproducible conductive performance, it is conceivable to strictly control the processing conditions in the resin composition preparation step and the molding step of the molded article. Process management is extremely complicated
Inefficient. In addition, the temperature distribution inside the extruder or the molding machine, the distribution of the shearing force applied to the molten resin and the flow characteristics of the resin are complicated, and even if such external control is performed, the results are not always satisfactory. Cannot be obtained.

[0005] Therefore, it is extremely important to provide a polyacetal resin having extremely stable conductivity even when extrusion and molding conditions are changed to some extent from the viewpoint of quality stability. Request is great.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyacetal resin material which solves the above-mentioned problems and has excellent conductive stability.

[0007]

Means for Solving the Problems In order to achieve the above-mentioned object, the present inventors have changed the viewpoint completely from the viewpoint of the related art, and have taken a detailed investigation into the molecular skeleton or the resin physical properties of the polyacetal resin as the base. As a result, a combination of modification of the polymer skeleton effective for achieving the object and a compounding component effective for such a polymer was found, and the present invention was completed.

That is, the present invention relates to a compound having 100 parts by weight of trioxane (a), a compound having two or more cyclic ether units in one molecule, and a compound (b) having 0.0005 to 2 parts by weight of one compound having one cyclic ether unit in one molecule. (C) 100 parts by weight of a polyacetal copolymer (A) obtained by copolymerizing 0 to 20 parts by weight and having a total terminal group content of 15 to 150 mmol / kg, one kind selected from carbon black and carbon fiber Or a polyacetal resin composition containing 0.1 to 30 parts by weight of two or more conductive carbon-based substances (B).

As described above, it is quite unexpected and surprising that the conductive stability of a polyacetal resin is remarkably improved by blending a conductive carbon-based material with a polyacetal copolymer modified by introducing a specific unit. That is.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. First, the polyacetal copolymer (A) used as a base resin in the present invention is a compound (b) containing trioxane (a) as a main component and having two or more cyclic ether units in one molecule, and, if necessary, It is obtained by copolymerizing a compound having one cyclic ether unit in one molecule.

The trioxane (a) used in the production of the polyacetal copolymer (A) as the base resin is a cyclic trimer of formaldehyde, and is generally reacted with an aqueous formaldehyde solution in the presence of an acidic catalyst. This is used after being purified by a method such as distillation. The trioxane (a) used in the polymerization preferably contains as little as possible impurities such as water, methanol and formic acid.

Next, the compound (b) having two or more cyclic ether units in one molecule used in the production of the polyacetal copolymer (A) refers to an epoxy unit,
Glycidyl unit, 1,3-dioxolan unit, 1,4-
It is a generic term for compounds having two or more cyclic ether units such as a butanediol formal unit, a diethylene glycol formal unit and a 1,3,6-trioxepane unit. Among them, two to four cyclic ether units
Compounds having 3 or 4 cyclic ether units are particularly preferred. The cyclic ether unit is preferably a glycidyl unit, and a diglycidyl ether compound, a triglycidyl ether compound and a tetraglycidyl ether compound are preferred or particularly preferred. Examples include 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, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, sorbitol polyglycidyl ether, sorbitan polyglycidyl ether, polyglycerol polyglycidyl ether, diglycerol poly Glycidyl ether and the like.

In particular, aliphatic compounds such as ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, hexamethylene glycol diglycidyl ether, glycerol triglycidyl ether, and trimethylolpropanetri Glycidyl ether and pentaerythritol tetraglycidyl ether are preferred. These compounds can be used alone or in combination of two or more for copolymerization with trioxane (a).

In one molecule, two cyclic ether units are contained.
The copolymerization amount of the compound (b) having at least one compound is 0.0005 to 2 parts by weight, preferably 0.001 to 1.5 parts by weight, particularly preferably 0.005 to 1.5 parts by weight, per 100 parts by weight of trioxane (a).
1 part by weight. If the copolymerization amount of the component (b) is too small, the effect of improving the conductive stability, which is the object of the present invention, cannot be obtained. If the amount is too large, the effect of improving the conductive stability is insufficient. Not only that, there is a possibility that a problem of surface roughness of the molded product and a problem of moldability due to a decrease in fluidity may occur.

The polyacetal copolymer (A) used in the present invention is preferably a copolymer obtained by further adding a compound (c) having one cyclic ether unit in one molecule as a copolymerization component. The compound (c) having one cyclic ether unit is not particularly essential for maintaining the conductive stability, which is a main object of the present invention, and for maintaining or improving rigidity and toughness, which are one of the objects of the present invention. However, in order to stabilize the polymerization reaction when producing the polyacetal copolymer (A) and to enhance the thermal stability of the produced polyacetal copolymer (A), the cyclic ether unit 1
It is extremely effective to use (c) as a copolymer component.

The compound (c) having one cyclic ether unit in one molecule includes ethylene oxide, propylene oxide, butylene oxide, epichlorohydrin, epibromohydrin, styrene oxide, oxetane,
3,3-bis (chloromethyl) oxetane, tetrahydrofuran, trioxepane, 1,3-dioxolan, ethylene glycol formal, propylene glycol formal, diethylene glycol formal, triethylene glycol formal, 1,4-butanediol formal, 1,5-pentanediol Formal, 1,
6-hexanediol formal and the like. Among them, ethylene oxide, 1,3-dioxolan, 1,4
-Butanediol formal and diethylene glycol formal are preferred.

In the polyacetal copolymer (A) used in the present invention, the compound (c) having one cyclic ether unit
Is from 0 to 20 parts by weight, preferably from 0.05 to 15 parts by weight, particularly preferably from 0.1 to 10 parts by weight, per 100 parts by weight of trioxane (a). Cyclic ether unit 1
If the copolymerization ratio of the compound (c) is too small, the copolymerization reaction becomes unstable and the thermal stability of the resulting polyacetal copolymer becomes poor, and conversely, the compound (c) having one cyclic ether unit When the copolymerization ratio of (1) is excessive, mechanical properties such as rigidity and strength, which are one of the object characteristics of the present invention, are reduced and become insufficient.

The polyacetal copolymer (A) used in the present invention is basically composed of the above trioxane (a), the compound (b) having two or more cyclic ether units in one molecule, and if necessary, The compound (c) having one cyclic ether unit in one molecule is used, and more generally, an appropriate amount of a molecular weight modifier is added thereto, and bulk polymerization is performed using a cationic polymerization catalyst. .

Examples of the molecular weight regulator include low molecular weight acetal compounds having an alkoxy group such as methylal, methoxymethylal, dimethoxymethylal, trimethoxymethylal, and oxymethylene di-n-butyl ether; and alcohols such as methanol, ethanol and butanol. Kind,
Examples thereof include an ester compound, an acid compound, and water. Among them, a low molecular weight acetal compound having an alkoxy group is particularly preferable. Further, by using these molecular weight regulators, it is possible to regulate the total terminal group content of the polyacetal copolymer (A) used in the present invention. Generally, as the molecular weight modifier increases, the total terminal group content of the obtained polyacetal copolymer increases. In determining the actual amount of the molecular weight modifier to be used, other factors affecting the total terminal group amount of the polyacetal copolymer, for example, the amount of the component (b), water contained in the monomer, and methanol contained in the monomer. In consideration of the amount of impurities, etc., the amount to be added is determined empirically or by a preliminary polymerization test so as to be in the range of the desired total terminal group amount.

The polyacetal copolymer (A) used in the present invention has a weight average molecular weight of 10,000 to 5,000.
00, particularly preferably 20000 to 15
It is 0000.

The polyacetal copolymer (A) used in the present invention has a total terminal group amount of 15 to 150 mmol / kg detected by ¹ H-NMR. Particularly, the total terminal group amount is preferably 20 to 100 mmol / kg. If the total amount of terminal groups is too small, the improvement in conductivity stability is slight, and the fluidity is extremely poor, making processing such as injection molding very difficult, and the surface roughness becomes remarkable. When the total amount of terminal groups is excessive,
It is not preferable because the melt viscosity is remarkably reduced, and sufficient conductivity stability cannot be obtained. In addition, remarkable reduction in toughness occurs, making it impossible to pelletize in a manufacturing process such as extrusion. Further, the polyacetal copolymer (A) preferably has a hemiformal terminal group content of 4 mmol / kg or less, particularly preferably 0 to 2 mmol / k.
g. If the amount of the hemiformal terminal group exceeds 4 mmol / kg, problems such as foaming due to decomposition of the polymer during molding may occur. In order to control the amount of hemiformal terminal group within the above range, it is preferable that impurities, particularly water, in the total amount of monomers and comonomer to be supplied to the polymer be 20 ppm or less, particularly preferably 10 ppm or less.

As the cationic polymerization catalyst, lead tetrachloride, tin tetrachloride, titanium tetrachloride, aluminum trichloride,
Zinc chloride, vanadium trichloride, antimony trichloride, phosphorus pentafluoride, antimony pentafluoride, boron trifluoride, boron trifluoride diethyl etherate, boron trifluoride dibutyl etherate, boron trifluoride dioxanate, trifluoride Boron trifluoride coordination compound such as boron trifluoride triethylamine complex compound, boron trichloride, t-butyl perchlorate, t-butyl perchlorate, hydroxyacetic acid, trichloroacetic acid,
Trifluoroacetic acid, inorganic and organic acids such as p-toluenesulfonic acid, triethyloxonium tetrafluoroborate, triphenylmethylhexafluoroantimonate,
Complex salt compounds such as allyldiazonium hexafluorophosphate and allyldiazonium tetrafluoroborate,
Alkyl metal salts such as diethylzinc, triethylaluminum, diethylaluminum chloride and the like, heteropoly acids, isopoly acids and the like can be mentioned. Among them, boron trifluoride, boron trifluoride diethyl etherate, boron trifluoride dibutyl etherate, boron trifluoride dioxanate, boron trifluoride acetic anhydrate, boron trifluoride triethylamine complex compound, etc. Boron fluoride coordination compounds are preferred. These catalysts can be used after being diluted with an organic solvent or the like in advance.

In producing the polyacetal copolymer (A) used in the present invention, the polymerization apparatus is not particularly limited, and a known apparatus may be used, and any method such as a batch type or a continuous type may be used. It is. The polymerization temperature is 65
It is preferred to keep it at ~ 135 ° C. Deactivation after polymerization is the product reactant discharged from the polymerization machine after the polymerization reaction, or
The reaction is performed by adding a basic compound or an aqueous solution thereof to the reaction product in the polymerization machine.

Examples of the basic compound for neutralizing and deactivating the polymerization catalyst include ammonia, amines such as triethylamine, tributylamine, triethanolamine and tributanolamine;
Alkaline earth metal hydroxide salts and other known catalyst deactivators are used. After the polymerization reaction, it is preferable to add these aqueous solutions to the product promptly to deactivate the product.
After such a polymerization method and a deactivation method, if necessary,
Washing, separation and recovery of unreacted monomers, drying and the like are performed by a conventionally known method.

The resin composition of the present invention is characterized in that the above-mentioned specific polyacetal copolymer (A) is used as a base resin, and a conductive carbon-based substance (B) is added thereto. Thereby, the conductive stability is dramatically improved as compared with the case where a general linear polyacetal resin is used as the base resin.

The conductive carbon-based material (B) used in the present invention is a general term for carbon black and carbon fibers generally used for the purpose of imparting conductivity to a resin. Species or two or more can be used.

The carbon black used in the present invention may be a commercially available carbon black generally referred to as conductive carbon black. One example is Ketjen Black ECX (manufactured by Lion Corporation). Generally, carbon black having a developed structure, a small particle diameter, a high porosity and a large surface area is desirable.

The carbon fiber used in the present invention is a fiber obtained by firing fibers such as acrylic fiber, rayon fiber, lignin fiber, petroleum-based or coal-based pitch, and is carbonaceous, graphite-based, flame-resistant. Etc. can be used. Among them, those using acrylic fiber and pitch as raw materials are preferable. Further, the carbon fiber may be blended with a specific amount of polyurethane or the like. In this case, it is effective to mix the composition by melt extrusion or the like, but it is preferable to add and adhere polyurethane or the like to the surface of the carbon fiber in advance, and further converge this as a binder. The diameter of the carbon fiber is preferably about 4 to 20 μm, particularly preferably 5 to 15 μm. One example is carbon fiber HT
There is A-C6US (made by Toho Rayon Co., Ltd.).

The amount of the conductive carbon-based material (B) selected from these carbon blacks and carbon fibers is one or two or more of which are based on 100 parts by weight of the polyacetal copolymer (A). It is 0.1 to 30 parts by weight, preferably 0.5 to 25 parts by weight. If the amount is less than 0.1 part by weight, the conductive performance is poor, which is not preferable.
If the amount is more than the weight part, the extrudability and molding processability of the composition are undesirably reduced.

In the present invention, the mechanism by which the resin composition comprising the polyacetal copolymer (A) and the conductive carbon-based substance (B) selected from carbon black and carbon fiber exhibits excellent conductive stability is unclear. Although not, the entanglement effect of molecules at the time of melting by introducing a specific cross-linking / branching structure into the polyacetal copolymer,
The unique viscoelastic properties associated with this, the disorder and non-uniformity of the crystal structure of the resin due to the specific cross-linking / branching structure, and the effect of the specific cross-linking / branching structure on the amorphous part are caused by the carbon-based substance (B) It is presumed that the variance is controlled. This is an effect produced only by a selective combination of a specific polyacetal copolymer (A) and a conductive carbon material (B) selected from carbon black and carbon fiber.

The resin composition of the present invention preferably contains various stabilizers selected as necessary. Examples of the stabilizer include any one or more of a hindered phenol compound, a nitrogen-containing compound, an alkali or alkaline earth metal hydroxide, an inorganic salt, and a carboxylate. Furthermore, as long as the objects and effects of the present invention are not impaired, if necessary, general additives for thermoplastic resins, for example, coloring agents such as dyes and pigments, lubricants, release agents, antistatic agents, and surfactants Alternatively, one or more kinds of organic polymer materials, inorganic or organic fibrous, powdery, and plate-like fillers can be added.

The composition of the present invention can be easily prepared by a known method generally used as a conventional method for preparing a resin composition. For example, after mixing each component, the mixture is kneaded and extruded with an extruder to prepare pellets, a predetermined amount of the pellets are mixed and subjected to molding to obtain a molded product having a desired composition after molding. Alternatively, any method such as a method of directly charging two or more can be used.

[0033]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples. still,
The evaluation was performed by the following method. [Evaluation of Conductivity Stability] Using a 30 mm twin-screw extruder, three types of pellet-shaped resin compositions having different melt-kneading conditions were prepared by changing the melt-kneading conditions as described below, and molded to measure the volume resistivity. Was done.

(Melting and kneading conditions) (Volume resistivity) Cylinder temperature 200 ° C., screw rotation speed 120 rpm R Cylinder temperature 230 ° C., screw rotation speed 120 rpm R ′ Cylinder temperature 200 ° C., screw rotation speed 180 rpm R ″ , The rate of change in volume resistivity R ′ (230 ° C., 120 rpm) / R (200
° C, 120 rpm) and R '' (200 ° C, 180 rpm) / R (200
° C, 120 rpm). The closer these values are to 1, the higher the stability of the volume resistivity.

The volume resistivity is 3 mm in thickness and 120 φ in diameter.
And a resistive chamber (main electrode: φ50, guard electrode: inner diameter φ70 / outer diameter φ80,
(Counter electrode: φ103) was set, and this was calculated by measuring the resistance value with a tester or an ultra-high resistance meter. Further, the molded product was adjusted to the shape of the electrode before measurement, coated with a conductive paste (Doitite S-1 manufactured by Fujikura Kasei), and air-conditioned (23 ° C., 50% RH) all day and night. Examples 1 to 7 A paddle was used by using a continuous mixing reactor having a barrel having a jacket through which a heat (cooling) medium was passed, a cross section having a shape in which two circles partially overlapped, and a rotary shaft with a paddle. Trioxane (a), a compound having two or more cyclic ether units in one molecule (b), a compound having one cyclic ether unit in one molecule while rotating the two rotating shafts marked with (C) was added at the ratio shown in Table 1, and methylal was continuously supplied as a molecular weight modifier, and boron trifluoride as a catalyst was continuously added and supplied in an amount of 0.005% by weight based on trioxane to perform bulk polymerization. Was. The reaction product discharged from the polymerization machine was immediately passed through a crusher and added to an aqueous solution containing 0.05% by weight of triethylamine at 60 ° C. to deactivate the catalyst. Further, after separation, washing and drying, a crude polyacetal copolymer was obtained.

Next, the crude polyacetal copolymer 1
4 wt% of a 5 wt% aqueous solution of triethylamine and pentaerythrityl-tetrakis [3-
(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] was added in an amount of 0.3% by weight, and the mixture was melt-kneaded at 210 ° C. with a twin-screw extruder to remove unstable portions. The obtained polyacetal copolymer was confirmed for its copolymer composition by ¹ H-NMR measurement using hexafluoroisopropanol d ₂ as a solvent, and was quantified from the peak area corresponding to each terminal, and the total terminal group amount was determined. I asked.

The carbon-based substance (B) shown in Table 1 was added to 100 parts by weight of the polyacetal copolymer (A) obtained by the above method.
Pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] as a stabilizer and 0.15 part by weight of melamine as a stabilizer, and a 30 mm twin screw extruder. At a cylinder temperature of 200 to 230 ° C and a screw rotation speed of 120 to 18
The mixture was melt-kneaded at 0 rpm while adjusting the conditions to prepare respective pellets, and then the conductive stability was evaluated using the pellets. Table 1 shows the results. Comparative Examples 1 to 101 When a polyacetal copolymer prepared without using compound (b) having two or more cyclic ether units in one molecule was used as a base resin, and two cyclic ether units in one molecule were used. When a polyacetal copolymer having a copolymerization amount of the compound (b) having the above-mentioned outside the range of the present invention is used as the base resin, a polyacetal copolymer having a total terminal group amount outside the range of the present invention is used as the base resin, and In the case where the amount of the system substance (B) was too small or too large, a pellet-shaped composition was prepared and evaluated in the same manner as in the examples.
Table 1 shows the results.

[0038]

[Table 1]

(B) Component b1: Trimethylolpropane triglycidyl ether b2: Pentaerythritol tetraglycidyl ether b3: 1,4-butanediol diglycidyl ether (c) Component c1: 1,3-dioxolan c2: Ethylene oxide (B) Ingredient B-1: Ketjen Black ECX (manufactured by Lion) B-2: Carbon fiber HTA-C6US (manufactured by Toho Rayon)

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yoshihisa Tajima 973 Miyajima, Fuji-shi, Shizuoka Polyplastics Co., Ltd. F-term (reference) 4J002 CB001 DA016 DA036 FA046 FD116 GQ02 4J032 AA05 AA33 AA39 AB06 AB32 AB34 AB35 AD28 AD31 AD32 AD33 AD34 AD35 AD37 AD38 AD41 AD44 AD45 AD46 AD47 AD51 AE02

Claims (7)

[Claims] 1. Compound (b) containing 100 parts by weight of trioxane (a) and two or more cyclic ether units in one molecule.
0005 to 2 parts by weight and 0 to 20 parts by weight of a compound (c) having one cyclic ether unit in one molecule,
100 parts by weight of a polyacetal copolymer (A) having a total terminal group amount of 15 to 150 mmol / kg, and one or more conductive carbon-based substances (B) selected from carbon black and carbon fiber (B) 0.1 to 30 A polyacetal resin composition containing parts by weight. 2. The compound (b) having two or more cyclic ether units in one molecule is a diglycidyl ether compound,
The polyacetal resin composition according to claim 1, wherein the composition is at least one member selected from the group consisting of a triglycidyl ether compound and a tetraglycidyl ether compound. 3. The compound (b) having two or more cyclic ether units in one molecule is ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, hexamethylene glycol diglycidyl. The polyacetal resin composition according to claim 2, wherein the polyacetal resin composition is at least one member selected from the group consisting of ether, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, and pentaerythritol tetraglycidyl ether. 4. The polyacetal resin composition according to claim 1, wherein the copolymerization ratio of the compound (c) having one cyclic ether unit in one molecule is 0.05 to 15 parts by weight. 5. The compound (c) having one cyclic ether unit in one molecule, wherein the compound (c) is selected from the group consisting of ethylene oxide, 1,3-dioxolan, 1,4-butanediol formal and diethylene glycol formal. The polyacetal resin composition according to any one of claims 1 to 4, which is at least one kind. 6. The polyacetal resin composition according to claim 1, wherein the total amount of the terminal groups of the polyacetal copolymer (A) is 20 to 100 mmol / kg. 7. The polyacetal copolymer (A) has a thickness of 4 mm.
The polyacetal resin composition according to any one of claims 1 to 6, which has a hemiformal terminal group content of ol / kg or less.