JPH07109375A - Sintered porous polyacetal resin article - Google Patents

Abstract

PURPOSE:To provide a sintered porous polyacetal resin article produced by using at least two kinds of polyacetal resins having different melting points, enabling easily sintering and molding, exhibiting excellent dimensional stability and having excellent mechanical strength and chemical resistance. CONSTITUTION:The porous material is composed of two or more kinds of polyacetal resins having melting point difference of >=5 deg.C. The porous material is preferably produced by using (A) 95-5wt.% of a polyacetal resin and (B) 5-95wt.% of one or more kinds of other polyacetal resins having a melting point different from that of the component A by >=5 deg.C, mixing the powder of the component A and the component B or melting and kneading the components A and B and pulverizing the mixture and sintering the mixture at a temperature below the melting point of the component having higher melting point. The porosity of the porous material is preferably 20-80%. The polyacetal resin is preferably incorporated with an antioxidant, an alkali metal compound, an alkaline earth metal compound, etc., to improve the thermal stability, weathering stability, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyacetal resin sintered porous body. More specifically, the present invention relates to a sintered polyacetal resin porous body having excellent chemical resistance and dimensional stability, which is formed by sintering two or more kinds of polyacetal resins having different melting points together.

[0002]

BACKGROUND OF THE INVENTION As is well known, polyacetal resins are engineering resins having excellent physical properties such as mechanical properties and electrical properties, and chemical properties such as chemical resistance and heat resistance. In recent years, it has been used in a very wide range of fields. In particular, since polyacetal resin has excellent chemical resistance, it is used for parts that come into direct contact with gasoline, kerosene, etc., caps for felt-tip pens, and the like. In the vicinity of these applications, there are parts that are required to have a filter function and the ability to impregnate pores with other substances. Polymeric porous materials are mainly formed by sintering using polyolefin, fluororesin, nylon resin, etc. To get the parts manufactured. Polyacetal resin has been tried to be applied to these parts due to its chemical resistance, heat resistance, etc., but the range of molding conditions in sintering molding is narrow, and since it is a crystalline resin, the volume change before and after crystallization is changed. However, in spite of the above-mentioned advantages, they have not been used in the past for sintered porous bodies. In order to meet these demands, conventionally known is a method of adding an inorganic filler such as glass beads, talc, calcium carbonate or the like. However, in these methods, the interfacial strength between the polyacetal resin and the inorganic filler cannot be obtained, and sufficient mechanical strength cannot be obtained. Further, since the shape of the inorganic filler is limited, there is a drawback that a desired pore size cannot be obtained. Therefore, it has been desired to develop a polyacetal resin material and a sintered porous body that have excellent mechanical strength, can be easily sintered and molded, and have excellent dimensional accuracy.

[0003]

DISCLOSURE OF THE INVENTION The present inventors have found that the polyacetal resin having excellent sinter moldability and high dimensional accuracy of the obtained polymer porous molded article without sacrificing the original properties of the polyacetal resin. As a result of intensive studies to develop the above, it was found that it is effective to use two or more kinds of polyacetal resins having different melting points together, and the present invention has been completed. That is, the present invention relates to a sintered porous body composed of two or more kinds of polyacetal resins having melting points different by 5 ° C. or more, and
(A) polyacetal resin, 95 to 5% by weight, and (B) one or more other polyacetal resin having a melting point different from that of the polyacetal resin of (A) by 5 ° C. or more, 5 to 95% by weight,
The present invention relates to a method for producing a sintered polyacetal resin porous body, which comprises mixing the powders of (A) and (B) or kneading (A) and (B) into powder and sintering the mixture.

The present invention will be described in detail below. The polyacetal resin of the components (A) and (B) used in the present invention is a polymer compound having an oxymethylene group (—CH ₂ O—) as a main constituent unit, and a polyoxymethylene homopolymer,
It includes any of copolymers, terpolymers and block polymers having a small amount of other constitutional units in addition to the oxymethylene group. Also, there is no particular limitation on the degree of polymerization.
The difference between the polyacetal resin of the component (A) and the polyacetal resin of the component (B) is the melting point (the melting point here means the peak top). That is, in the present invention, as the components (A) and (B),
It is characterized in that a polyacetal resin having a difference in melting point of 5 ° C. or higher, preferably 10 ° C. or higher is used in combination. Here, when the difference in melting point between the two components is less than 5 ° C., the molding conditions in the sintering molding are narrow, and the strength of the obtained sintered molded product becomes weak and fragile, or only dimensional accuracy is low. . Incidentally, (B)
When two or more components are used, the difference in melting point between the respective components (A) is 5 ° C. or more, and the difference in melting points between the components (B) is not a particular problem. Such a polyacetal resin having a different melting point can be appropriately prepared depending on the presence or absence of the copolymerization component and the ratio thereof.

The mixing ratio of the polyacetal resins (A) and (B) used here is such that (A) / (B) is 95/5 to 5 by weight.
A range of 5/95 is preferred. If the content is out of this range, the molding conditions in the sintering molding are narrow, the strength of the obtained sintered molded product is small and it becomes brittle, or only the one with low dimensional accuracy is obtained, and the cracked product is obtained. It may occur. Further, it is desirable to add various known stabilizers to the polyacetal resin which is a constituent of the present invention to reinforce the thermal stability, weather stability and the like. For this purpose, it is desirable to use one or more known antioxidants, nitrogen-containing compounds, alkali or alkaline earth metal compounds and the like in combination. Further, the composition of the present invention can be optionally colored by appropriately adding various carbon blacks and other various face dyeing amounts. Further, according to the purpose, in order to impart desired properties, conventionally known additives, nucleating agents, releasing agents, antistatic agents, other surfactants, or organic polymer materials other than polyacetal resin, inorganic, organic It is possible to add one or more reinforcing agents and the like.

The polyacetal resin which is a constituent of the present invention can be prepared by the equipment and method generally known as a method for preparing a synthetic resin composition. That is, the necessary components are mixed and kneaded using a single-screw or twin-screw extruder,
After extrusion, the pellets may be crushed, or polyacetal resins having different melting points may be crushed separately and then mixed. In addition, the compounds such as the stabilizer and the additives may be added at any arbitrary stage.

The sintered porous body of the present invention is, for example, (A), (B)
Prepare each powder and mix them, or
It can be produced by melt-kneading (A) and (B) into a powder, and then sinter-molding at a predetermined temperature by an ordinary method. The sintering temperature is generally lower than or equal to the higher melting point of the components (A) and (B). Further, as is apparent from the examples described below, the present invention enables sintering even at a relatively low temperature,
There is an advantage that the range of molding conditions in the sintering molding is wide.

Further, when the porosity of the sintered porous body of the present invention is calculated by the following formula, those having a porosity of 20 to 80% have particularly excellent properties. When used as a base material for oil-impregnated bearings, it is a desirable porous body because it has good liquid immersion and filterability. When the porosity is lower than 20%, the liquid immersion property and the filterability are insufficient and there is a problem in practical use.
If it is higher than 80%, the mechanical strength is insufficient and problems occur. Φ (porosity) = {1-W / (V × ρ)} × 100 (%) W: Weight of molded product (g) V: Volume of molded product (cm ³ ) ρ: Polyacetal true specific gravity (1.41 g / cm ³⁾ )

[0009]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited thereto. In the comparative examples and examples, the methods used for evaluating the characteristic values are as follows. (1) Sintering molding Predetermined amount of polyacetal resin powder (100
~ 200 mesh pass product) inside dimensions 100 L x 30 W x 20 H
(Mm) is placed in a rectangular female mold with an opening at the top, and the male mold is inserted through the upper opening, and 10 kg at 150 kg / cm ²
It was pressed and compressed to a thickness of 0 L × 30 W × 10 mm, placed in a heating furnace at a predetermined temperature in a nitrogen stream, and sintered for 20 minutes. (2) Molding shrinkage ratio The molded product dimension (L) of the sintered compact obtained in (1) was measured, and the molding shrinkage ratio was calculated from the following formula. MS (molding shrinkage rate) = (L ₀ −L) / L ₀ L: Molded product size L ₀ : Mold size (3) Molded product strength (1) Measured flexural strength using the molded product did.
The test method was according to ASTM D 790.

Comparative Examples 1 and 2 Polyacetal resin A having a melting point of 175 ° C. (manufactured by Asahi Kasei Corp.,
Tenac 5010, a homopolymer) and a polyacetal resin B having a melting point of 165 ° C. (manufactured by Polyplastics Co., Ltd., DURACON M90-44, copolymer) are ground separately.
A powder of the desired particle size was obtained. In the following, using each individually,
Sintering was performed by the above method. The results are shown in Table 1. Examples 1 to 5 The polymer powders used in Comparative Examples 1 and 2 were mixed at room temperature in the proportions shown in Table 1, and then sintered and molded at the molding temperature shown in Table 1. The results are shown in Table 1. Example 6 The respective polymer powders used in Comparative Examples 1 and 2 were mixed at room temperature in the proportions shown in Table 1, and then kneaded using a twin-screw extruder, and then pulverized to obtain a powder having a desired particle size. Got the body Hereinafter, sintering molding was performed at the molding temperature shown in Table 1. The results are shown in Table 1.

Example 7 Polyacetal resin C (prototype copolymer) having a melting point of 170 ° C.
And polyacetal resin B having a melting point of 165 ° C. are pulverized separately,
A powder of the desired particle size was obtained. Hereinafter, sinter molding was performed by the same method as in Examples 1 to 5. The results are shown in Table 1.

[0012]

[Table 1]

[0013]

As is apparent from the above description and the examples, by mixing two or more kinds of polyacetal resins having different melting points, it becomes possible to carry out sintering molding having a practical molding condition range. The obtained sintered molded product has dimensional accuracy,
It became a practical sintered porous body with good mechanical strength and excellent chemical resistance.

Claims (3)

[Claims] 1. A sintered porous body composed of two or more kinds of polyacetal resins having melting points different by 5 ° C. or more. 2. The polyacetal resin sintered porous body according to claim 1, which has a porosity of 20 to 80%. 3. A polyacetal resin (A), 95 to 5% by weight
And (B) one or more other polyacetal resins having different melting points of 5 ° C. or more with respect to the polyacetal resin of (A), 5 to 95% by weight, and mixing the powders of (A) and (B), or (A)
A method for producing a sintered polyacetal resin porous body, which comprises melt-kneading (B) and (B), converting the powder into powder, and sintering the powder.