JP2000103827A - Polyacetal copolymer and use thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyacetal copolymer yielding a resin material which has high mechanical properties and generates little noise at sliding in a low temperature environment. SOLUTION: This copolymer is obtained by copolymerizing 100 pts.wt. trioxane, 0.05 to 20 pts.wt. cyclic ether compound copolymerizable with trioxanes and 0.001 to 10 pts.wt. monofunctional glycidyl compound. The shear loss modulus G" of the solid viscoelasticity of the copolymer at -20 deg.C is 3×107 Pa or larger. Preferably, the cyclic ether compound copolymerizable with trioxanes is ethylene oxide or 1,3-dioxolane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyacetal copolymer and a sliding component which can provide a resin material having excellent mechanical properties and low noise during sliding in a low-temperature environment.

[0002]

BACKGROUND OF THE INVENTION Polyacetal resins have well-balanced mechanical properties,
It is widely used in the fields of automobiles, electric and electronic products, etc. because of its excellent friction and wear resistance, chemical resistance, heat resistance, electric properties, and the like. Due to its light weight, easy moldability, balanced mechanical properties, etc., it is being used for even more parts and components. However, the required characteristics in such a field are gradually becoming more sophisticated, and as one example, further improvement in sliding characteristics as well as general physical properties is desired. In particular, recently, as the number of parts using resin increases, the number of parts in which resin parts come into contact with each other and slide is increasing. Of course, the problem of sliding noise, of course, has been increasingly taken up, not to mention the amount. In particular, sliding noise tends to be generated at low temperatures, which is a serious problem for materials used even in low-temperature environments such as parts of automobiles. In general, it is known that sliding noise is likely to occur when sliding between resins, and this tendency is particularly remarkable in a low temperature state. The mechanism that causes this is unknown, and it is often not possible to suppress the generation of sliding noise even if the friction coefficient is improved. Therefore, in order to suppress the occurrence of sliding noise, grease is applied to the sliding surface, the sliding partner material is changed to a metal or the like, and the shape of the sliding component is changed.
However, the application of grease complicates the working process and causes troubles such as adhesion of grease to other parts. Changing or changing the shape of the sliding partner limits the freedom of design,
This results in increased costs and the like. As described above, the conventionally known methods are not yet sufficient from the viewpoint of practicality, and materials capable of suppressing the generation of sliding noise are desired.

[0003]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have carried out a detailed study into the molecular skeleton or resin physical properties of a polyacetal resin, and have completed the present invention. It has arrived. That is, the present invention
A polyacetal copolymer obtained by copolymerizing (a) 100 parts by weight of trioxane, (b) 0.05 to 20 parts by weight of a cyclic ether compound copolymerizable with trioxane, and (c) 0.001 to 10 parts by weight of a monofunctional glycidyl compound. And the viscoelastic torsional loss modulus G ″ of the copolymer at −20 ° C.
Is 3 × 10 ⁷ Pa or more and a polyacetal copolymer and its use.

[0004]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the polyacetal copolymer of the present invention will be described in detail. First, the trioxane (a) used in the present invention is a cyclic trimer of formaldehyde, which is generally obtained by reacting an aqueous formaldehyde solution in the presence of an acidic catalyst, and which is obtained by a method such as distillation. It is used after purification. The trioxane (a) used in the polymerization preferably contains as little as possible impurities such as water, methanol and formic acid.

The cyclic ether compound (b) copolymerizable with trioxane (a) in the polyacetal copolymer of the present invention 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. In the present invention, the copolymerization amount of the cyclic ether compound (b) is
(A) 0.05 to 20 parts by weight of trioxane 100 parts by weight
Parts by weight, preferably 0.1 to 15 parts by weight, particularly preferably 0.3 to 10 parts by weight. Cyclic ether compound (b)
If the amount is too small, the polymerization reaction becomes unstable, and the thermal stability of the resulting polyacetal copolymer becomes poor,
Conversely, when the copolymerization ratio of the cyclic ether compound (b) is excessive, not only mechanical properties such as strength and rigidity are reduced, but also the sliding properties aimed at by the present invention become insufficient.

Next, the monofunctional glycidyl ether compound (c) in the polyacetal copolymer of the present invention is a general term for an organic compound having one glycidyl group in the molecule. Glycidyl ethers of alcohols or aromatic alcohols or their (poly) alkylene glycol adducts and glycidol, glycidyl esters of aliphatic carboxylic acids or aromatic carboxylic acids or their (poly) alkylene glycol adducts and glycidol A representative example is given. Specific examples include methyl glycidyl ether, ethyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, 2-methyloctyl glycidyl ether, phenyl glycidyl ether, p-tertiary butyl phenyl glycidyl ether, sec-butyl phenyl glycidyl ether, n-butylphenyl glycidyl ether, phenylphenol glycidyl ether, cresyl glycidyl ether, dibromocresyl glycidyl ether,
Glycidyl acetate, glycidyl stearate and the like can be mentioned. The copolymerization amount of the monofunctional glycidyl compound of the component (c) is based on 100 parts by weight of the trioxane of the component (a).
0.001 to 10 parts by weight, preferably 0.01 to 10 parts by weight,
Particularly preferably, it is 0.1 to 5 parts by weight. If the copolymerization amount of the component (c) is too small, the effect of improving the sliding noise, which is the main object of the present invention, cannot be obtained.
Problems such as deterioration of mechanical properties such as rigidity occur. Further, (c) a monofunctional glycidyl compound having a molecular weight of 1
It is preferable to use one of 100 to 1000. (C) If the molecular weight of the monofunctional glycidyl compound is too large, the branched chain of the polyacetal copolymer produced by the copolymerization becomes long, disturbing the crystallinity and the like of the resin and impairing its basic properties, Undesirable effects may also occur on the intended sliding characteristics. Conversely, if the molecular weight of the component (c) is too small, the effect on the sliding properties, which is the object of the present invention, will be extremely small.

The polyacetal copolymer of the present invention is basically prepared by adding the above-mentioned trioxane (a), cyclic ether compound (b) and monofunctional glycidyl compound (c) to a suitable amount of a molecular weight regulator as required. Then, it is obtained by a method such as performing bulk polymerization using a cationic polymerization catalyst. here,
The polyacetal copolymer of the present invention requires that the torsional loss modulus G ″ of solid viscoelasticity at −20 ° C. is 3 × 10 ⁷ Pa or more, and it is the first time that this requirement is satisfied. It has excellent sliding characteristics with less noise when moving, because its loss elastic modulus, which is a viscous term, is 3 ×
It is considered that when the pressure is 10 ⁷ Pa or more, a lubricating layer is formed on the sliding surface, and the self-lubrication characteristic of polyoxymethylene is exhibited even in a low-temperature environment. On the other hand, when the torsional loss modulus G ″ is less than 3 × 10 ⁷ Pa, the low temperature environment (−
Sliding noise is liable to occur when sliding under 20 ° C), and especially between the same materials, the occurrence of sliding noise is remarkable.

In the present invention, tan δ (G ″) is measured by a torsional forced vibration type dynamic viscoelasticity measuring device (New Polymer Experimental Science 8 Physical Properties of Polymer (1) Thermal and Mechanical Properties, Polymer Calculated from the measurement at a frequency of 1 Rad./sec., Using the range of deformation in the linear range.The shape of the measurement sample is 0.8 mm in thickness and 12 in width.
mm, length 40 mm. Measure after sufficiently setting at the measurement temperature.

In order to obtain a polyacetal copolymer satisfying the above viscoelastic requirements, structural units derived from (b) a cyclic ether compound and (c) a monofunctional glycidyl compound in the molecular chain of the polyacetal copolymer. Are preferably dispersed uniformly. For this purpose, in the production of the polyacetal copolymer by polymerization, the cyclic ether compound (b), the glycidyl compound (c) and the catalyst are previously uniformly mixed, and An effective method is to add a melt of trioxane (a) separately supplied to a polymerization machine to perform polymerization, or to further mix the homogeneous mixture with trioxane (a) and then supply the mixture to a polymerization machine to perform polymerization. In particular, the reaction rate of the glycidyl compound (c) is often lower than that of the other components (a) and (b),
It is extremely effective to mix the component (c) and the catalyst in advance. In this way, by pre-mixing and leaving in a uniform solution state, the dispersion state of the branched structure derived from the glycidyl compound is improved, and a polyacetal copolymer satisfying the viscoelastic requirement is obtained. Excellent sound characteristics.

In producing the polyacetal copolymer of the present invention comprising the above-mentioned components and satisfying the above-mentioned requirements, the polymerization apparatus is not particularly limited.
A known device is used, and any method such as a batch method and a continuous method is possible. The polymerization temperature is preferably maintained at 65 to 135 ° C. The deactivation after the polymerization is performed by adding a basic compound or an aqueous solution thereof to a product reactant discharged from the polymerization machine after the polymerization reaction or a reactive product in the polymerization machine.

The cationic polymerization catalyst used in the present invention includes lead tetrachloride, tin tetrachloride, titanium tetrachloride, aluminum trichloride, zinc chloride, vanadium trichloride, antimony trichloride, phosphorus pentafluoride, and antimony pentafluoride. , Boron trifluoride, boron trifluoride diethyl etherate, boron trifluoride dibutyl etherate, boron trifluoride dioxanate, boron trifluoride acetic unhydrate,
Boron trifluoride coordination compound such as boron trifluoride triethylamine complex compound, inorganic acid such as perchloric acid, acetyl perchlorate, t-butyl perchlorate, hydroxyacetic acid, trichloroacetic acid, trifluoroacetic acid, p-toluenesulfonic acid and the like Organic acids, triethyloxonium tetrafluoroborate, triphenylmethylhexafluoroantimonate, allyldiazonium hexafluorophosphate, complex salt compounds such as allyldiazonium tetrafluoroborate, diethyl zinc, triethylaluminum,
Alkyl metal salts such as diethylaluminum chloride,
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 the polyacetal copolymer of the present invention, in addition to the above components, a chemical component capable of forming a branched or crosslinked structure can be used in combination. Examples of the component capable of forming a branched or crosslinked structure include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, hexamethylene glycol diglycidyl ether, resorcinol diglycidyl ether, and bisphenol A Examples include diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polybutylene glycol diglycidyl ether, glycerin and derivatives thereof, and pentaerythritol and derivatives thereof.

The molecular weight modifier used in the present invention includes:
Methylal, methoxymethylal, dimethoxymethylal, trimethoxymethylal, oxymethylenedi-n-
Examples thereof include low molecular weight acetal compounds having an alkoxy group such as butyl ether, alcohols such as methanol, ethanol and butanol, and ester compounds. Among them, a low molecular weight acetal compound having an alkoxy group is particularly preferable. The amount of these molecular weight modifiers is not particularly limited as long as the effects of the present invention are not impaired.

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.

Further, if necessary, a stabilization treatment is carried out by a known method, such as decomposition removal of an unstable terminal or sealing of an unstable terminal with a stable substance, and various necessary stabilizers are blended.

As the stabilizer used herein, one or more of a hindered phenol compound, a nitrogen-containing compound, an alkali or alkaline earth metal hydroxide, an inorganic salt, a carboxylate and the like are used. Can be mentioned. Furthermore, as long as the present invention is not impaired, if necessary, general additives for thermoplastic resins, for example, dyes, coloring agents such as pigments, lubricants, nucleating agents, release agents, antistatic agents, surfactants, Alternatively, one or more kinds of organic polymer materials, inorganic or organic fibrous, powdery, plate-like fillers and the like can be added.

The degree of polymerization of the polyacetal copolymer of the present invention is not particularly limited, and the degree of polymerization and the like can be adjusted according to the purpose of use and the molding means. The melt index (MI) measured under a load of 2.06 kg is preferably 1 to 100 g / 10 min, and particularly preferably 2 to 90 g / 10 min.

[0018]

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 method described below is as follows. [Measurement of Sliding Sound Generation Surface Pressure] A cylindrical thrust test piece (contact area: 2.0 cm ² ) was molded by injection molding using the resin materials prepared in Examples and Comparative Examples described later. Simultaneously, a cylindrical thrust test piece was molded in the same manner using DURACON AW-01 manufactured by Polyplastics Co., Ltd. as a resin to be slid.

Next, a thrust test piece made of the resin to be slid was used as a fixed-side thrust test piece, and a thrust test piece made of the test resin material was used as a rotation-side thrust test using a thrust-type friction and wear tester (Suzuki-type tester). As a piece, it was slid at a constant speed of 1 cm / sec in an environment of -20 ° C. The pressure (surface pressure) applied to the sliding surface was increased from about 0.06 MPa to 0.1 MPa every minute, and the surface pressure at which squeak noise was continuously generated was defined as the sliding sound generation surface pressure. [Initial mechanical strength] The tensile strength was measured according to the method of ASTM D638.

Examples 1 to 7 A continuous mixing reactor constituted by a barrel having a jacket through which a heat (cooling) medium passes and having a cross section having a shape in which two circles partially overlap with each other, and a rotary shaft with paddles. While rotating the two rotating shafts with paddles at 150 rpm,
Add component (a) and continuously supply methylal as a molecular weight regulator. Then, in components (b) and (c), a dibutyl ether solution of boron trifluoride dibutyl etherate as a catalyst is added to trioxane. In terms of boron trifluoride
A homogeneous mixture mixed to be 0.08% by weight was continuously added and supplied to perform bulk polymerization. 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. Then, the crude polyacetal resin 1
4 parts by weight of a 5% by weight aqueous solution of triethylamine with respect to 00 parts by weight, pentaerythrityl-tetrakis [3-
(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] was added and melt-kneaded at 210 ° C. with a twin-screw extruder to remove unstable portions. Further, pentaerythrityl-tetrakis [3- (3,3)
5-di-tert-butyl-4-hydroxyphenyl) propionate] and 0.15 parts by weight of melamine, and melt-kneaded at 210 ° C. with a twin-screw extruder to obtain a pellet-like polyacetal copolymer. Obtained.

Comparative Examples 1 to 3 As shown in Table 1, when the component (c) was not used and when a small amount outside the specified range was used, a pellet-like polyacetal copolymer was prepared in the same manner as in Example 1. Then, the above evaluation was performed. The results are also shown in Table 1. Comparative Examples 4 and 5 Components (b) and (c) were added simultaneously with component (a) without uniform mixing with the catalyst, and the catalyst and the molecular weight regulator were added in the same manner as in Example except that each was added alone. Further, a pellet-like polyacetal copolymer composition was prepared on the basis of the same copolymer composition as in the examples. The obtained polyacetal copolymer did not satisfy the definition of the torsional loss modulus G ″. The evaluation results are also shown in Table 1.

[0022]

[Table 1]

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4H104 BB09R BB10R BB32R BC09R BD06R CB14A CB14R EA30A LA20 PA01 QA11 4J002 CB001 CH021 CH031 CH041 GM00 4J032 AA05 AA33 AA34 AA35 AA36 AB36 AD06 AB36 AB06 AD38 AD41 AD45 AD46 AD47 AD51 AE02 AE14 AF04 AF05 AF08

Claims (5)

[Claims] (1) 100 parts by weight of trioxane, (b)
Cyclic ether compound copolymerizable with trioxane 0.05-
20 parts by weight and (c) the monofunctional glycidyl compound 0.001 to 10
A polyacetal copolymer obtained by copolymerizing parts by weight, wherein the copolymer has a solid viscoelastic torsional loss modulus G ″ at −20 ° C. of 3 × 10 ⁷ Pa or more. Polyacetal copolymer. 2. The polyacetal copolymer according to claim 1, wherein (b) the cyclic ether compound copolymerizable with trioxane is ethylene oxide or 1,3-dioxolane. 3. The method according to claim 1, wherein (c) the monofunctional glycidyl compound is 100 to
The polyacetal copolymer according to claim 1 or 2, which is a compound selected from the group consisting of glycidyl ether and glycidyl ester having a molecular weight of 1,000. 4. A sliding component comprising a resin material mainly comprising the polyacetal copolymer according to claim 1. 5. The sliding part according to claim 4, wherein the sliding part is used as at least one part in sliding between resin parts.