JPH0439319A - Branched polyacetal copolymer resin for sliding member - Google Patents

Abstract

PURPOSE:To obtain the title resin excellent in frictional and wear characteristics and processability and mechanical strength, thus suitable for audio and video- related parts by copolymerization between trioxane, cyclic ether as comonomer and diglycidyl compound. CONSTITUTION:The objective resin can be obtained by reaction between (A) 99.88 - 85.0wt.% of trioxane, (B) as comonomer, 0.1 - 10 (pref. 0.3 - 5)wt.% of cyclic ether and/or cyclic formal (pref. ethylene oxide, dioxolan, trioxepan or 1,4-butanediol formal) and (C) 0.02 - 5 (pref. 0.1 - 3.0)wt.% of a diglycidyl compound (pref. alkylene oxide diglycidyl ether).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a polyacetal copolymer with excellent friction and wear properties.

More specifically, the present invention relates to a branched polyacetal copolymer resin for sliding members, which is obtained by polymerizing trioxane, cyclic ethers, and diglycidyl compounds, and has excellent friction and wear characteristics, as well as excellent processability and mechanical strength.

[Conventional technology and its issues]

Polyacetal resin has well-balanced mechanical properties and is excellent in friction and wear properties, chemical resistance, heat resistance, and electrical properties, so it is widely used in fields such as automobiles and electrical/electronic products.

Polyacetal resin has excellent chemical, thermal, and mechanical properties even without the use of special additives, but depending on the field of use, various reinforcing agents and additives may be added to further improve the above properties. Attempts have been made to improve various physical properties by incorporating improving agents.

For example, in order to further improve the friction and wear characteristics, it is possible to add and mix fluororesins, polyolefin resins, silicone resins, and other resins to polyacecool resin, and to add solid lubricants such as graphite and molybdenum disulfide. , various mineral oils, silicone oils, fatty acids, etc. are added.

By incorporating these additives, the initial friction and wear characteristics of polyacecool resin can be improved to some extent, but this is insufficient for long-term use, and the physical properties originally possessed by the resin are significantly sacrificed. There are many cases where
Furthermore, problems specific to the combination of various additives as shown below have been recognized, and improvements have been sought.

As for such problems, for example, fluororesins and polyolefin resins have poor compatibility with polyacetal resins, so they tend to cause peeling on the surface of molded products or generate precipitates in molds.

Furthermore, in the case of solid lubricants such as graphite and molybdenum disulfide, the sliding properties are gradually impaired due to abrasion powder produced by the compounding agents, and the mechanical properties are also deteriorated.

Additionally, the addition of lubricating oil can cause problems such as poor biting into the screw and poor plasticization during extrusion or molding, and depending on the environmental conditions in which the molded product is used (especially at high temperatures), the lubricating oil may be applied to the surface of the molded product. oozing has been observed, and there are some restrictions on its use.

Further, although conventional improvement methods may temporarily exhibit excellent frictional properties, when used for a long period of time, problems arise such as generation of wear particles and melting of the sliding surface. If an attempt is made to further increase the amount of the above-mentioned two compounding agents added in order to improve these properties, the physical properties will deteriorate more significantly and processing will become even more difficult.

As described above, the conventionally known methods of adding additives have various problems and are not necessarily satisfactory.

[Means to solve the problem]

The present inventors have conducted intensive studies to develop a polyacetal resin that has good mechanical properties and excellent friction and wear properties without the need for adding a lubricant.
It has been discovered that a special polyacetal copolymer made by polymerizing specific monomers has extremely improved friction and wear characteristics without the addition of other additives, and has excellent processability, mechanical strength, etc., and has developed the present invention. I was able to complete it.

That is, the present invention comprises: (A) 99.88 to 85.0% by weight trioxane;
(B) 0.1 to 10% by weight of cyclic ether and/or cyclic formal as comonomer, and (C) 0.02 to 10% by weight.
This invention provides a branched polyacetal copolymer resin for sliding members obtained by polymerizing 5% by weight of a diglycidyl compound.

Hereinafter, the branched polyacetal copolymer of the present invention will be explained in detail.

First, trioxane (A), which is the main monomer constituting the polyacecool copolymer of the present invention, and comonomer (B) are well-known substances conventionally used in the production of polyacetal copolymers.

That is, trioxane is a cyclic trimer obtained from formaldehyde. Further, the cyclic ether and cyclic formal as the comonomer (B) are compounds represented by the following general formula (2).

R''C-0 R6 [In the formula, R3, R4, R5 and Rh mean a hydrogen atom, an alkyl group, or an alkyl group substituted with halogen, and each may be the same or different. R7 is a methylene group or an oxy a methylene group or a methylene group or an oxymethylene group each substituted with an alkyl group or a halogenated alkyl group (in this case, p represents an integer of O to 3), or a compound of the formula -<C8zhrpublishedCl(- or -(0- Hz-CH
z) means a divalent group represented by CI'h- (in this case, q represents an integer of 1 to 4). Alkyl group is 1-5
carbon number, and 1 to 3 hydrogen atoms may be replaced by halogen atoms, especially chlorine atoms. ] Examples of such cyclic ethers and cyclic formals include epichlorohydrin, ethylene oxide, 1,3-dioxolane, diethylene glycol formal, and 1,4-
Examples include butanediol formal, 1,3-dioxane, propylene oxide, and the like. Furthermore, cyclic esters such as β-propiolactone and vinyl compounds such as styrene or acrylonitrile are also used. Particularly preferred cyclic ethers and cyclic formals include one or more selected from ethylene oxide, dioxolane, trioxepane, and 1,4-butanediol formal.

The amount of cyclic ether and cyclic formal used is 90.1 to 10% by weight, preferably 0.3 to 5% by weight of the total mixed monomer. If the amount is less than 0.1% by weight, the processability and thermal stability, which are characteristics of polyacetal copolymers, will be insufficient, and if it exceeds 5.0% by weight, the production itself will be difficult.

Next, the diglycidyl compound (C) which causes the polyacetal resin to develop branching, which is a feature of the present invention, will be explained.

The diglycidyl compound used in the production of the polyacetal copolymer of the present invention is an aliphatic ether having two glycidyl groups at its ends, and preferably a compound represented by the following general formula (3) or (4) is used.

CHI-CH-CI, -0-(CHI-CHI-0 bitter C
)lx-CHC1(z (3)\0/
\0/(m is an integer from 2 to 5) CHz-CB-CHz-0beCHz+T-0-CHz-
CHCFIz (4)\0 /
', 0 /' (l is an integer of 2 to 6) Examples of the diglycidyl compound represented by the above formula (3) or (4) include diethylene glycol diglycidyl ether, triethylene glycol diglycidyl ether, butanediol diglycidyl ether, etc. Among them, butanediol diglycidyl ether is particularly preferred.

The amount of such diglycidyl compound used is 0.02 to 5.0
% by weight (preferably 0.1 to 3.0% by weight. 0.
If the amount is less than 0.02% by weight, the excellent friction and wear properties that are the object of this application will hardly be exhibited, and if the amount is more than 5.0% by weight, excessive crosslinking reaction will occur during polymerization, making the production itself difficult. Processability, mechanical strength, etc. of the polymer product are significantly reduced, which is not preferable.

The polymerization of the polyacetal copolymer for sliding members of the present invention is as follows:
In addition to the above constituent components, a low molecular weight acetal compound (D
) R'0 (CHI0), R'' (]) [where n is an integer of 1 to 10, R1 and R2 are alkyl groups having 1 to 5 carbon atoms, and R1 and R1+ may be the same or different ] can be carried out in the presence of

Low molecular weight acetal compound (D) represented by formula (1)
Examples include methylal, methoxymethylal, dimethoxymethylal, trimethoxymethylal, oxymethylene di-butyl ether, and methylal is preferred.

The amount of the substance (D) added is adjusted between 0 and 1000 ppm depending on the required molecular weight (melt viscosity) of the branched copolymer.

The method for polymerizing such a polyacetal copolymer may be carried out in accordance with the well-known method for polymerizing a trioxane copolymer. That is, a cationically active catalyst is generally used as the catalyst. Examples of such catalysts include Lewis acids, especially halides such as boron, tin, titanium, phosphorus, arsenic and antimony, such as boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentachloride, trichloride, etc. Compounds such as phosphorus fluoride, arsenic trifluoride and antimony trifluoride and their complexes or salts, protic acids such as trifluoromethanesulfonic acid,
Verchloric acid, esters of protic acids, especially esters of perchloric acid and lower aliphatic alcohols (e.g. tertiary butyl verchloric acid ester), anhydrides of protic acids, especially mixed anhydrides of perchloric acid and lower aliphatic carboxylic acids (e.g. acetyl verchlorate), or isopoly acids, heteropolyacids (e.g. phosphomolybdic acid), or triethyloxonium hexafluorophosphate,
Examples include triphenylmethyl hexafluoroarzenate and acetyl hexafluoroborate. Among these, boron fluoride or a coordination compound of boron fluoride and an organic compound (eg, ether) is the most common and suitable.

The polymerization reaction can be carried out either batchwise or continuously.
Further, although solution polymerization, melt bulk polymerization, etc. may be used, a method using a liquid monomer and obtaining a solid powder-like polymer as the polymerization progresses is most suitable. In this case, an inert liquid medium can also be present if necessary.

As a polymerization device, a generally used reaction tank with a stirrer can be used for the Hutch type, and for continuous type, there are a co-kneader twin-screw continuous extrusion mixer, a twin-screw paddle type continuous mixer, and other conventional polymerization equipment. Continuous polymerization equipment such as trioxane proposed in 2007 can be used.

The polymerization temperature ranges from 64 to 120°C.

Within this range, relatively low temperatures are more desirable.

Further, the polymerization time is related to the amount of catalyst and is not particularly limited, but a polymerization time of 0.5 to 100 minutes is generally selected. The polymer taken out from the exit of the polymerization machine after a predetermined period of time is usually in the form of lumps or powder, and is stabilized through post-processes such as separating some or all of the unreacted polymers and stabilizing them using conventional methods. It is possible to obtain a copolymer with high properties.

190°C 12°16 of branched polyacetal copolymer resin
The melting index under kg standard load (^STM D-1238-577) is in the range of 0.01 to 60 (g/10 min), and from the viewpoint of practical mechanical properties, moldability, etc. 5
It is more preferably in the range of 30 to 30. Such branched polyacetal copolymer resins generally have a high dependence of viscosity on shear rate, and are characterized by good moldability considering their high molecular weight.

Additionally, the branched polyacetal resin copolymer thus obtained surprisingly has frictional properties that cannot be obtained with linear copolymers, and can be used as is without adding any known lubricants. It also exhibits the friction and wear characteristics generally required for sliding members, has improved mechanical strength, and does not have the drawbacks of conventional resins containing lubricants, and is suitable as a material for sliding parts.

That is, the branched polyacetal copolymer of the present invention has excellent friction and wear properties not only at room temperature but also in high-temperature environments, and also has excellent friction and wear properties under high-temperature environments, and also has excellent friction and wear properties under the so-called limit PV, which is the condition for melting at the contact surface during continuous running. Value (Contact pressure (P) at the limit where the resin does not melt x Linear sliding velocity (■))
shows a tendency to be higher than that of conventional linear polyacetal resin, and 11! during continuous running. The increase in friction coefficient is gradual, and it exhibits excellent friction properties both in the short and long term.
Furthermore, since no lubricating oil or the like is added, there are no problems such as seepage during processing, molding, or use, making the copolymer particularly suitable as a material for sliding parts in high-temperature environments. It is a feature of the present invention that it has not been previously known that branched polyacetal copolymers exhibit such properties. That is, the polyacecool copolymer of the present invention has a friction coefficient of 0.00 after running for 24 hours as measured by the measurement method described below.
35 or less.

The resin of the present invention can be mixed with a linear polyacetal homopolymer or a polyacetal copolymer whose main chain is mostly composed of oxymethylene chains, as long as the purpose is not impaired.

Furthermore, in order to impart physical properties to the resin of the present invention depending on the intended use, various known additives such as various stabilizers, colorants, lubricants, mold release agents, nucleating agents, antistatic agents, Of course, it is also possible to use a composition in which other surfactants, different polymers, organic modifiers, etc. are added during polymerization or after polymerization and before molding.

〔Example〕

The present invention will be explained in more detail with reference to Examples below.
The present invention is not limited to this.

Examples 1 to 6 A barrel having a cross section in which two circles with an inner diameter Bosm partially overlap, an effective length of 1.3 m, a jacket with a jacket for passing a heat medium on the outside, and a number of paddles that engage with each other on the inside thereof. Using a continuous mixing reactor consisting of two rotating shafts, hot water at 80"C was passed through the jacket, the two rotating shafts were rotated in different directions at a speed of 100 rpm, and one end of the reactor had the composition shown in Table 1. of trioxane mixture at a rate of 10 kg/hour, and at the same time, a predetermined amount of a cyclohexane solution of boron trifluoride dibutyl etherate is continuously added to the same place to perform copolymerization, and then discharged from the other end. The resulting reaction mixture was immediately poured into water containing 0.1% triethylamine to deactivate the polymerization catalyst.Then, the polymer was washed with acetone and air-dried for stabilization, resulting in a branched polyacetal copolymer. Obtained union.

Comparative Examples 1 to 3 Polymerization was carried out in the same manner as in Examples using (A) trioxane and (B) cyclic ether shown in Table 1, using a small amount or no use of (C) diglycidyl compound, and stabilization step. Through this process, a substantially linear polyacetal polymer was obtained.

The polyacecool (co)polymers obtained in Examples 1 to 6 and Comparative Examples 1 to 3 were molded into test pieces, and the friction coefficient and tensile strength were measured. The results are summarized in Table 1.

In addition, the test method and measurement method are as follows.

■) Coefficient of Dynamic Friction Using a test piece with the shape shown below, a surface pressure of 10 kg/cm" and a linear speed of 300 mm/sec were applied using a precious wood type friction and wear tester.
Measurements were made at room temperature under the following conditions using steel 555C as a counterpart material.

Test piece; inner diameter 20.0 mm, outer diameter 25.6 mm, contact area 2.0" 2) Tensile strength 8 According to STM D 638.

3) Melt index (Ml) Melt index (A
ST? 'ID-1238, 57T) [Effects of the Invention] As is clear from the above description and examples, the branched polyacetal resin obtained by polymerizing trioxane, cyclic ether and/or cyclic formal, and diglycidyl compound is Compared to conventional polyacetal resins, it has excellent friction and wear properties, especially improved properties for long-term use, has improved strength, and has no processing problems, making it extremely preferable as a material for sliding parts. In addition, the polyacecool resin for sliding parts of the present invention does not have any difficulties in extrusion or molding, which have traditionally been a problem with this type of material, and also does not allow separation of components, so it can be used in applications such as automobiles, electrical, electronics, etc. Suitable for parts that require sliding properties, such as audio and video related parts.

Claims (1)

[Scope of Claims] 1 (A) 99.88 to 85.0% by weight of trioxane, (B) 0.1 to 10% by weight of cyclic ether and/or cyclic formal as a comonomer, and (C) 0.1 to 10% by weight of cyclic ether and/or cyclic formal. A branched polyacetal copolymer resin for sliding members obtained by polymerizing 02 to 5% by weight of a diglycidyl compound. 2. The branched polyacetal copolymer resin for sliding members according to claim 1, wherein component (B) is one or more selected from ethylene oxide, dioxolane, trioxepane, and 1,4-butanediol formal. 3. The branched polyacetal copolymer resin for sliding members according to claim 1 or 2, wherein the diglycidyl compound (C) is alkylene oxide diglycidyl ether. 4. Claims 1 to 3, wherein the polyacetal copolymer is polymerized in the presence of (D) a low molecular weight acetal compound represented by the following general formula (1):
The branched polyacetal copolymer resin for sliding members according to any one of the above. R^1O(CH_2O)nR^2(1) [However, n is an integer from 1 to 10, and R^1 and R^2 are alkyl groups having 1 to 5 carbon atoms and may be the same or different]