JPH05255571A - Composite resin composition - Google Patents

Abstract

PURPOSE:To prepare the title compsn. low in friction coefficient and abrasion loss, high in strengths and stiffness, and excellent in dimensional accuracy by compounding a polyacetal resin with specified amts. of zinc oxide whisker and an abrasion resistance improver. CONSTITUTION:The title compsn. is prepd. by compounding a polyacetal resin with 5-40wt.% zinc whisker and 0.5-30wt.% abrasion resistance improver. The resin, excellent in sliding properties, has been used in applications where excellent sliding properties are required, e.g. for a part of a precision instrument or an electric or electronic apparatus. Applications are now increasing in areas where stiffness, strengths, and dimensional accuracy are also required. For improving these properties, an inorg. filler such as glass fiber or talc is usually used. However, such a filler increases the friction coefficient and abrasion loss and does not give a compsn. usable in areas requiring excellent sliding properties. The title compsn. because of the synergistic action of zinc oxide whisker and the abrasion resistance improver, is low in friction coefficient and abrasion loss, high in strengths and stiffness, and excellent in dimensional accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite resin composition excellent in sliding friction performance used for parts of precision equipment and electronic / electrical equipment, and more specifically, it has a small coefficient of friction, a small amount of wear and excellent dimensional accuracy. And a composite resin composition.

[0002]

2. Description of the Related Art Polyacetal resins have been used in precision equipment, parts of electronic / electrical equipment, etc., particularly in places where slidability is required, by taking advantage of their excellent slidability.

However, in recent years, along with the expansion of applications of polyacetal resins, there are increasing cases in which not only slidability but also rigidity, strength, and dimensional accuracy are required. In that case, an inorganic substance such as glass fiber or talc is usually added and used.

[0004]

However, since these conventional composite resin compositions have a high coefficient of friction and a large amount of wear, they cannot be used in places where sliding friction performance is required, and glass fiber and talc cannot be used. Etc. had a problem that the orientation in the molded product was strong and the dimensional accuracy was poor in combination with the high crystallinity of the polyacetal resin.

In view of such problems, it is an object of the present invention to provide a composite resin composition having a small coefficient of friction, a small amount of wear, and excellent rigidity, strength and dimensional accuracy.

[0006]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors on the above problems, it is effective to add a zinc oxide whisker and a specific wear improving agent together to a polyacetal resin. And that the addition amount of a specific wear-improving agent is limited to a certain range and when the surface treatment agent for zinc oxide whiskers is limited to a specific surface treatment agent, the present invention is completed, and the present invention is completed. Came to. The composite resin composition of the present invention has the following requirements.

That is, a composite resin composition comprising a polyacetal resin, a zinc oxide whisker as a main component, and an abrasion improver.

Preferably, the amount of zinc oxide whiskers added is 5
˜40% by weight, the amount of the wear modifier added is 0.5 to 30% by weight, and the zinc oxide whiskers have a core portion and needle-shaped crystal portions extending in different directions from the core portion. The length from the base of the crystal part to the tip is 2 μm or more, and the wear improver is fluororesin, silicone, high density polyethylene,
It is selected from one or more fatty acid esters.

[0009]

The polyacetal resin used in the present invention has a main raw material of trioxane which is formaldehyde or a trimer of formaldehyde obtained by oxidation of methanol. Most of the polyoxymethylene homopolymer or the main chain of the polyacetal resin is more than oxymethylene chain. And polyacetal copolymers, terpolymers, etc., which are commercially available. Also, the degree of polymerization is not particularly limited.

The greatest feature of the present invention is to use a zinc oxide whisker having a tetrapot-like structure having a core portion and needle-like crystal portions extending from the core portion in different directions. As you can imagine, the three-dimensional isotropy of the physical properties in the matrix resin is guaranteed, and the difference in the shrinkage rate between the injection direction of the molded product and the direction perpendicular to the injection direction is minimized to achieve high dimensional accuracy. It is possible to secure and simultaneously obtain the original reinforcing property as a filler.

The amount of zinc oxide whiskers added is 5 to 40% by weight, more preferably 5 to 30% by weight. If the amount added is more than this range, not only the kneading becomes difficult, but also the wear characteristics are adversely affected, which is not preferable, and if the amount added is less than this range, the effect of adding zinc oxide whiskers is not exhibited.

Zinc oxide whiskers have an average fiber length of about 20.
Since it is a fine fiber of ˜30 μm, it is possible to secure the surface smoothness of the molded product and to obtain the reinforcing effect while minimizing the reduction of the friction coefficient. The greatest difference from other fibrous, particulate, and plate-like inorganic substances is that the uniform dispersion can be easily realized and the deterioration of the abrasion resistance can be minimized.

FIG. 1 is an external view of a zinc oxide whisker used in the present invention, and its shape specificity can be easily confirmed.

The zinc oxide whiskers are obtained by heat-treating metallic zinc particles and are extremely mass-producible by themselves. They are easily dispersed by a usual resin kneading method such as a Banbury mixer, a screw extruder, a roll mill, There is no need to add any special structure or construction method.

Further, the zinc oxide whiskers are preferably surface-treated in advance with a silane compound and / or a fatty acid in order to improve the binding force with the matrix resin and to minimize the deterioration of the polyacetal resin.

[0016] The silane compound are those represented by the general formula _{Y-R-Si-X 3} , Y is an amino group, an epoxy group,
It is an organic functional group such as a vinyl group, preferably an epoxy group. Further, R is an alkylene group or the like, and X is a hydrolyzable group such as chlorine, an alkoxy group or an acetone group.

It is essential that the fatty acid has 12 to 28 carbon atoms, and those belonging to these include stearic acid, lauric acid, myristic acid, palmitic acid, oleic acid, linoleic acid, linolenic acid, and these fatty acids. The metal salt of is included, and among them, saturated fatty acids having 12 to 28 carbon atoms are particularly preferable.

Further, the zinc oxide whiskers preferably have a length from the base to the tip of the needle-shaped crystal portion of 2 μm or more. This is because zinc oxide whiskers having a diameter of 2 μm or less act only as spherical particles in the matrix resin, and the reinforcing effect cannot be obtained.

Needle-shaped zinc oxide whiskers may be present in the matrix resin, but these are broken pieces of needle-shaped crystal parts extending in a plurality of directions, acting as needle-shaped fibers and broken. It has been experimentally confirmed that it is isotropically uniformly dispersed in the molded product after that, and it does not impair the main characteristics of the present invention.

The wear modifier functions synergistically with the zinc oxide whiskers present in the molded product, and contributes to the reduction of the friction coefficient and wear amount. Fluororesin, silicone, high density polyethylene, molybdenum disulfide. , Fatty acid ester,
Examples thereof include low molecular weight polyethylene wax, metal soap, fatty alcohol, polyhydric alcohol, mineral oil, vegetable oil and synthetic lubricating oil. Among them, especially fluororesin, silicone,
It is preferable to add one or more of high-density polyethylene and fatty acid ester.

The amount of the wear modifier added is 0.5 to 30% by weight, preferably 1 to 20% by weight. If the added amount is less than this, the wear improving effect cannot be obtained, and if the added amount is more than this, for example, in the case of silicone or fatty acid ester, it exudes to the surface of the molded product and causes a sticky phenomenon, and it also bites into the screw during molding. If it causes a defect and is remarkable, molding becomes difficult, which is not preferable. Further, in the case of high density polyethylene or fluororesin, the dispersibility is deteriorated, the effect of improving wear is lowered, and kneading is difficult, which is not preferable.

The fluororesin here means tetrafluoroethylene, which is a polymer of tetrafluoroethylene obtained by thermal decomposition of CHClF ₂ , or tetrafluoroethylene-obtained by copolymerizing tetrafluoroethylene and hexafluoropropylene. Hexafluoropropylene copolymer, CF
₂ Cl-CFCl ₂ of ethylene trifluoride copolymers of the resulting chlorotrifluoroethylene by dechlorination, there is polyvinylidene fluoride or the like as a radical polymerization of vinylidene fluoride, the coefficient of friction as a wear improving agents,
Ethylene tetrafluoride having a low surface energy is preferable.
The average particle size of the fluororesin is preferably 30 μm or less. If the average particle size exceeds 30 μm, it becomes difficult to uniformly disperse the particles in the molded product, and the effect of improving wear of tetrafluoroethylene cannot be sufficiently exhibited.

The silicone is silicone oil, silicone rubber, silicone resin or the like which is generally called organopolysiloxane. In particular, silicone oil made of dimethylpolysiloxane or the like having a relatively low degree of polymerization that does not impair fluidity, and silicone grease obtained by adding metal soap or the like to silicone oil are preferable.

The high-density polyethylene has a density of about 0.94 g / cm ³ or more obtained by polymerizing ethylene, has a crystal structure in which long-chain branches having 6 or more carbon atoms mostly occupy, and Also included are copolymers with copolymerizable α-olefins and the like. The high-density polyethylene has an average particle size of 200 μm or less and a molecular weight of 50,000 to 8,000.
And more preferably a molecular weight of 2,000,000.
The above-mentioned so-called ultra-high density polyethylene is preferable. If the average particle size exceeds 200 μm, the surface of the molded product becomes rough and the coefficient of friction increases, which is not preferable. If the molecular weight is less than 50,000, it becomes difficult for the high density polyethylene to exist in the form of particles in the molded product due to kneading.
It is not preferable because it does not contribute to the improvement of wear characteristics. Further, if the molecular weight exceeds 8,000,000, kneading becomes extremely difficult, and if it is remarkable, molding becomes difficult, which is not preferable.

The fatty acid ester is an ester of a fatty acid having 5 to 23 carbon atoms and a monohydric or polyhydric alcohol having 2 to 30 carbon atoms, and more preferably a fatty acid having 12 to 22 carbon atoms and 2 to 22 carbon atoms. Esters with monohydric or polyhydric alcohols. Examples of the esters belonging to these include stearyl stearate, pentaerythritol monostearate, pentaerythritol tetrastearate, behenyl behenate, myristyl myristate, and the like.

[0026]

EXAMPLES Some examples of the present invention will be described below, but the present invention is not limited to these examples.

The samples, test equipment, and test methods used in each example are as follows.

(Sample) * Polyacetal resin manufactured by BASF Engineering Plastics Co., Ltd. Ultraform W2320 * Zinc oxide whisker manufactured by Matsushita Amtec Co., Ltd., Panatetra (registered trademark) (surface treated product) * Fluorine resin Mitsui DuPont Fluorochemicals Co., Ltd. Made, MP1300 * Silicone, Shin-Etsu Silicon Co., Ltd., KF-96 * High-density polyethylene Mitsui Petrochemical Co., Ltd., Miperon (registered trademark) XM
-220 * Fatty acid ester stearyl stearate * Glass fiber Nippon Sheet Glass Co., Ltd., RESO3-TP87 * Talc Fuji Talc Co., Ltd. PKP-80 (Test method) * Bending strength: ASTM-D790 * Bending elastic modulus: ASTM -D790 * Tensile breaking strength: ASTM-D638 * Friction and wear test: Using Suzuki type wear tester. Counterpart material S4
5C (no lubrication).

The friction coefficient and the specific friction amount were measured at a friction speed of 30 cm / sec, a load of 10 kg / cm ² , and a friction distance of 10 km.

* Molding shrinkage ratio: A mold conforming to ASTM-D955 is used.

Thickness 1 mm, diameter 102 mm, gate width 12.
7 mm, mold temperature 80 ° C * Sample preparation: Screw extruder (temperature 180 ° C,
Screw diameter 44 mm, biaxial) Injection molding machine (temperature 190 ° C, pressure 850 kg / cm ² , total cycle 60 sec) The results of each Example and Comparative Example are summarized in Tables 1 to 4.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

[0035]

[Table 4]

(Examples 1 to 3 and Comparative Examples 1 to 3 and 9) In Examples 1 to 3, 5, 10 and 30% by weight of zinc oxide whiskers surface-treated with epoxysilane were added to the polyacetal resin. It is an example of addition, and it can be seen that an excellent reinforcing effect is recognized with the addition amount and almost no anisotropy of molding shrinkage is recognized. Further, compared with only the polyacetal shown in Comparative Example 1, the dynamic friction coefficient hardly changed, and the increase of the specific wear amount was suppressed to the minimum, and the sliding property, strength, rigidity, and dimensional accuracy were kept as they were. Which is an excellent composite resin composition.

Comparative Examples 2 and 3 are examples in which glass fibers and talc were added to the polyacetal resin in an amount of 20% by weight, which are examples that have been used much more than before. Characteristically, when using these glass fibers and talc, although simple rigidity and strength can be obtained, slidability is remarkably deteriorated as in the comparative example, and in particular, the specific wear amount is remarkably increased. Since the orientation of the fibers and talc is large, the anisotropy of the molding shrinkage becomes large, and high dimensional accuracy cannot be obtained. The above two points are the biggest differences from the compositions shown in Examples 1 to 3. That is the point of interest of the present invention.

Further, Comparative Example 9 is an example in which the zinc oxide whiskers were not surface-treated with the same composition as in Example 3, and the mechanical properties and slidability were worse than in Example 3, and It is not preferable for the purpose of the invention. Further, the polyacetal was decomposed during the kneading, and it was extremely difficult to draw the strand.

(Example 4) A zinc oxide whisker surface treating agent was stearic acid with the same composition as in Example 3. In this case, although the mechanical properties were slightly lowered as compared with Example 3, satisfactory values were obtained for the slidability, the anisotropy relaxation of the molding shrinkage, and the reinforcing effect, which are the main objects of the present invention. I understand that

(Examples 5 to 8 and Comparative Examples 4 and 10) In Examples 5 to 8, 10, 20% by weight of zinc oxide whiskers subjected to epoxysilane surface treatment and 5, 1 of fluororesin were used.
This is an example in which 0% by weight is added, and it can be seen that the addition of fluorine further improves the slidability as compared with Examples 1 to 3. What is more characteristic is that the specific wear amounts shown in Examples 6 and 8 are smaller than the addition of the fluororesin alone shown in Comparative Example 10, which means that the zinc oxide whiskers and the fluororesin act synergistically. It was realized. In addition, Example 1
It can be seen that the reinforcing effect and the effect of alleviating the anisotropy of molding shrinkage, which are observed in Nos. 3 to 3, are maintained.

In Comparative Example 4, the fluororesin was added to Comparative Example 2
It is an example in which 0 wt% was added, and although the slidability was improved by the effect of fluorine, it was found to be insufficient, and the synergistic effect seen in Examples 5 to 8 was not confirmed.

(Examples 9 to 13 and Comparative Examples 5 to 8 and 11)
Examples 13 to 14 are 10% by weight of zinc oxide whiskers surface-treated with epoxysilane, silicone,
High-density polyethylene, 3-10 wt% of fatty acid ester
Is added in the range of. Similar to what was seen in Examples 5 to 8, also in Example 9 and Comparative Example 11, Example 12 and Comparative Example 12, and Example 13 and Comparative Example 13, zinc oxide whiskers and various wear modifiers were synergistic. It is easy to understand that they are working.

Comparative Examples 5 to 8 are examples in which glass fiber, talc, and silicone, high-density polyethylene, and fatty acid ester are added together. Similar to Comparative Example 4, the addition of these wear modifiers improves the slidability. However, the addition of silicone, high-density polyethylene, and fatty acid ester has not been found to have any slidability improving effect.

Example 14 20% by weight of zinc oxide whiskers surface-treated with an epoxysilane-based fluororesin,
It is an example in which each high-density polyethylene is added by 10% by weight,
Even when a plurality of types of wear modifiers are added, Examples 1 to 1
The basic effect seen in No. 13 can be found, and it can be seen that the slidability is further improved.

Various general antioxidants, stabilizers such as ultraviolet absorbers, which are not particularly added in the above-mentioned embodiment,
It goes without saying that flame retardants, nucleating agents and general pigments, dyes, etc. can be added arbitrarily, and one or more kinds of conventionally known various organic polymers are added within a range not impairing the characteristics of the present invention. Is also possible. Examples of organic polymers corresponding to these are polyurethane, ethylene vinyl acetate copolymer, ethylene-alkyl acrylate copolymer,
Examples thereof include a styrene-butadiene-acrylonitrile copolymer, a polyacrylate multi-phase graft copolymer, and a thermoplastic elastomer.

Further, although not particularly added in the present invention, the rigidity,
The addition of a conventionally known general reinforcing substance for the purpose of further increasing the strength can be arbitrarily performed within a range that does not impair the purpose of the present invention. It can be easily understood by considering the shape specificity of the zinc oxide whiskers and the synergistic effect of the zinc oxide whiskers and the wear modifier.
As those belonging to these inorganic substances, glass beads, calcium carbonate, quartz powder, silica, magnesium carbonate, barium sulfate, clay, alumina powder, glass powder, granular inorganic substances such as graphite, glass fiber, carbon fiber, wollastonite, Examples thereof include fibrous reinforcing materials such as dolomite, asbestos, silicon carbide whiskers, potassium titanate whiskers, whisker-like calcium carbonate, metal fibers and aramid fibers, and plate-like reinforcing materials such as mica, glass flakes, talc and metal foil.

[0047]

INDUSTRIAL APPLICABILITY As described above, the composite resin composition of the present invention has a small coefficient of friction, a small amount of wear, and excellent dimensional accuracy in addition to strength and rigidity, and is suitable for various precision instruments and electronic / electrical equipment parts. In particular, it can be effectively used in places where sliding friction performance is required. .

[Brief description of drawings]

FIG. 1 is an electron micrograph of a zinc oxide whisker used in the present invention.

[Procedure amendment]

[Submission date] April 21, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

FIG. 1 is an electron micrograph showing a crystal structure of zinc oxide whiskers.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number in the agency FI technical display location C08L 23:06 83:04) (72) Inventor Kazumi Nanomura 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Appliance Industry Co., Ltd. (72) Inventor Kojiro Matsuo 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (11)

[Claims] 1. A composite resin composition containing a polyacetal resin and zinc oxide whiskers as main components. 2. The composite resin composition according to claim 1, wherein a wear modifier is added to the polyacetal resin. 3. The composite resin composition according to claim 2, wherein the zinc oxide whiskers are added in an amount of 5 to 40% by weight and the wear modifier is added in an amount of 0.5 to 30% by weight. 4. A zinc oxide whisker has a core portion and needle-shaped crystal portions extending from the core portion in different four-axis directions, and the length from the base to the tip of the needle-shaped crystal portion is 2 μm or more. The composite resin composition according to claim 1 or 2, wherein 5. The composite resin composition according to claim 1, wherein the zinc oxide whiskers are surface-treated with a silane compound and / or a saturated fatty acid. 6. The functional group Y in the general formula of a silane-based compound Y—R—Si—X ₃ R: an alkylene group or the like X ₃ : a hydrolyzable group such as chlorine, an alkoxy group, or an acetone group is an epoxy group. The composite resin composition according to claim 5, wherein 7. The composite resin composition according to claim 5, wherein the saturated fatty acid has 12 to 28 carbon atoms. 8. The wear improving agent is one or two of fluororesin, silicone, high density polyethylene and fatty acid ester.
The composite resin composition according to claim 2, wherein the composite resin composition is selected from at least one species. 9. The composite resin composition according to claim 8, wherein the fluororesin is tetrafluoroethylene having an average particle size of 30 μm or less. 10. The high-density polyethylene has an average particle size of 20.
0 μm or less and molecular weight of 50,000 to 800,000
It is 0, The composite resin composition of Claim 8 characterized by the above-mentioned. 11. The fatty acid ester is obtained from a fatty acid having 5 to 32 carbon atoms and a monohydric or polyhydric alcohol having 2 to 30 carbon atoms. The composite resin composition described.