JPH0977838A - Modified polyoxymethylene copollymer, its production and composition containing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a modified polyoxymethylene copolymer having improved sliding property and compatibility and useful as a comopatibilizer, etc., by copolymerizing a vinyl ether having a specific higher aliphatic hydrocarbon as a comonomer co-existing with trioxane, etc. SOLUTION: This copolymer contains an oxymethylene group as a main repeating unit, a copolymerizing unit of the formula (R is a >=5C aliphatic hydrocarbon) in an amount of 0.01-10mol% of the oxymethylene unit and an oxyalkylene unit [-(CH2 )n -O-((n) is 2-4)] as a copolymerizing unit in an amount of 0-10mol% of the oxymethylene unit, and has 2,000-400,000 weight-average molecular weight. For instance, trioxane is used as a main monomer and copolymerized with a vinyl ether of the formula: CH2 =CH-O-R in an amount of 0.03-30mol% of trioxane and cyclic ether or cyclic formal in an amount of 0-30mol% of trioxane in the presence of a cation-activating catalyst.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a modified polyoxymethylene copolymer having improved slidability and compatibility, a method for producing the same, and a composition containing the same.

[0002]

2. Description of the Related Art Polyoxymethylene (hereinafter abbreviated as POM) (co) polymer has been known as an engineering plastic material for many years and because of its well-balanced mechanical properties, electrical properties and chemical resistance. Widely used as automobile parts, electric and electronic equipment parts, machine parts and other structural materials. However, PO
The M (co) polymer has a very low affinity with other substances, and various problems occur when attempting modification by blending with other materials or coating. For example, when blending other modifiers etc., satisfactory physical properties cannot be obtained due to poor affinity and compatibility with the mating material, and separation and surface peeling occur and the appearance of the molded product remarkably increases. May be damaged.
Further, in many cases, sufficient adhesion cannot be obtained for painting and adhesion. In addition, POM (co) polymers have mechanical strength,
It is widely used for sliding materials such as bearings and gears because it has excellent lubricity and anti-friction and wear characteristics as well as durability, but recently, more advanced lubrication characteristics are required, There are many cases where higher level sliding characteristics are required. In order to improve this point, a surface coating of a lubricant such as grease or a composition containing various lubricants has been proposed so far. However, the POM (co) polymer has a low affinity with other substances, and it is often difficult to retain the lubricant or the like for a long period of time.
In many cases, inconveniences such as exudation and adhesion on the surface occur when the molded product is used for a long period of time.

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the problems in the prior art as described above, has high reactivity as a comonomer in the copolymerization reaction with trioxane, and
Almost all of them are chemically introduced and bonded into M to give excellent lubricity and slidability to POM itself, so that there is no inconvenience such as sticking to the mold surface or exuding to the surface of the molded product during molding. It is an object of the present invention to provide a modified POM copolymer which is stable and has excellent compatibility and compatibility with other additives, and a composition thereof.

[0004]

Means for Solving the Problems As a result of research to achieve the above object, the present inventors have found that a vinyl ether having a specific higher aliphatic hydrocarbon (—R) represented by the following formula (2) is used as a comonomer. The inventors have found that a long-chain aliphatic hydrocarbon group can be efficiently introduced into POM by copolymerizing it with coexisting with trioxane and the like, and achieved the above object. That is, the present invention relates to an oxymethylene group
The main repeating unit is (-CH ₂ -O-), the copolymerized unit represented by the following general formula (1) is contained in an amount of 0.01 to 10 mol% based on the oxymethylene unit, and an oxyalkylene unit (-
(CH ₂ ) _n -O-) (wherein the carbon number n of alkylene is 2 to 4) is a copolymerized unit and is 0 to 10 relative to the oxymethylene unit.
A modified polyoxymethylene copolymer having a weight average molecular weight of 2000 to 400,000, including mol%,

[0005]

Embedded image

(Provided that -R represents an aliphatic hydrocarbon having 5 or more carbon atoms) and trioxane as main monomers, and vinyl ether (comonomer A) represented by the following general formula (2) is 0.03 with respect to trioxane. ~ 30 mol%, cyclic ether or cyclic formal (comonomer B) 0-30 mol% with respect to trioxane, copolymerization in the presence of a cationically active catalyst, the production of a modified polyoxymethylene copolymer CH ₂ = CH-OR (2) (where -R represents an aliphatic hydrocarbon having 5 or more carbon atoms) and a composition containing such a modified polyoxymethylene copolymer.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

The modified POM copolymer of the present invention comprises an oxymethylene group (-CH ₂ -O-) as a main repeating unit, and the copolymerized unit represented by the general formula (1) is 0.01 to oxymethylene unit. 10 mol%, preferably 0.02 to 2 mol%, weight average molecular weight of 2000 to 400000, preferably 3000 to
It is a modified polyoxymethylene copolymer of 300,000. Here, it is indispensable that -R in the above formula (1) is an aliphatic hydrocarbon having 5 or more carbon atoms in order to obtain excellent friction characteristics and slidability, and preferably 8 to 8 carbon atoms. 32, particularly preferably an aliphatic hydrocarbon group having 11 to 32 carbon atoms.
Further, the aliphatic hydrocarbon group constituting —R is preferably a higher alkyl group, and a part of the hydrogen may be replaced with another element or group. Further, the repeating unit constituting the main chain of the modified polyoxymethylene copolymer of the present invention,
Further, an oxyalkylene unit (-(CH ₂ ) _n -O-) (however,
The number of carbon atoms n of the alkylene unit may be 2 to 4) as a copolymerized unit, and in this case, the introduction ratio of the oxyalkylene copolymerized unit is 0 to 10 mol% with respect to the oxymethylene unit, preferably 0.1 to 5 It is mol%, and either may be introduced randomly or in a block form. The terminal group of the POM copolymer of the present invention is not particularly limited,
As with the end groups of the conventional POM polymer or copolymer end groups _{(e.g., - (CH 2) n OH} , -CH 2 -OH, -O-CH 3, -OCOCH 3
Etc.), or the structural unit (1) may form a terminal.

Next, a typical method for producing the modified POM copolymer of the present invention will be described. The modified POM copolymer of the present invention is copolymerized with trioxane as a main monomer and vinyl ether containing a specific long-chain aliphatic hydrocarbon represented by the above formula (2) as a comonomer A in the presence of a cationic active catalyst. This is the basic constitution, and in this case, further comonomer B
It is preferable to use a cyclic ether or a cyclic formal together. It was confirmed by ¹ H-NMR analysis that the compound of the formula (2) had high reactivity in the copolymerization reaction with trioxane and was efficiently introduced into the produced polymer. still,
The method for producing the compound of the formula (2) is not particularly limited, but it is generally synthesized from R-OH and acetylene using an alkaline catalyst, purified, and subjected to a copolymerization reaction. (2)
The amount of the compound of the formula used during the polymerization is 0.03 to 30 mol%, preferably 0.05 to 10 mol% based on the main monomer trioxane. It is particularly preferably 0.1 to 5 mol%. If the amount is too small, the above-mentioned desired effect cannot be obtained, and if it is too large, the copolymerization reaction is hindered, and the mechanical strength of the POM copolymer produced is remarkably lowered, which is not preferable. Next, the cyclic formal used as the comonomer B in the present invention has the following general formula (3) or (3 ′).

[0010]

Embedded image

(Wherein n is an integer of 2 to 4, X is hydrogen or an alkyl group having 4 or less carbon atoms, which may be the same or different, but is preferably hydrogen). Examples thereof include cyclic formal such as 1,3-dioxolane, 1,3-dioxane, 1,4-butanediol formal, and diethylene glycol formal, with 1,3-dioxolane being particularly preferred. The cyclic ether used as the comonomer B includes ethylene oxide, propylene oxide, oxetane, etc. Among them, ethylene oxide is preferable. The amount of the comonomer B used, which is related to the amount of the comonomer A, is 0 to 30 mol%, preferably 0.3 to 15%, and particularly preferably 0.5 to 10% based on trioxane. If the amounts of comonomer A and B are too small, the thermal stability is remarkably inferior, and if it is too large, a high catalyst concentration is required, side reactions frequently occur, and the melting point of the produced polymer is lowered and the mechanical strength is low. Is also not preferable. A particularly preferred total amount of comonomers A and B is 0.3 to 15 mol% based on trioxane.

Further, as the polymerization catalyst in the present invention,
Common cationically active catalysts are used. Such cationically active catalysts include Lewis acids, especially boron, tin,
Halides such as titanium, phosphorus, arsenic and antimony,
For example, boron trifluoride, tin tetrachloride, titanium tetrachloride,
Compounds such as phosphorus pentachloride, phosphorus pentafluoride, arsenic pentafluoride and antimony pentafluoride, and complex compounds or salts thereof, protic acids such as trifluoromethanesulfonic acid, perchloric acid, esters of protic acids, especially perchloric acid. With lower aliphatic alcohols (eg, perchloric acid tertiary butyl ester), anhydrides of protic acids, in particular mixed anhydrides of perchloric acid with lower aliphatic carboxylic acids (eg, acetylparkrate), or isopoly acids, Examples thereof include heteropoly acid (for example, phosphomolybdic acid), triethyloxonium hexafluorophosphate, triphenylmethylhexafluoroarzenate, acetylhexafluoroborate and the like. Among them, boron trifluoride or a coordination compound of boron trifluoride and an organic compound (for example, ethers) is most general and suitable. The amount of the catalyst used in the present invention is 1 × 10 6 with respect to the total amount of the monomers.
^-5 to 1 × 10 ^-2 mol% is preferable.

The weight-average molecular weight of the modified polyoxymethylene copolymer of the present invention is 2000-400000, preferably 3000-30.
It is 0000 and can be adjusted to any value within the above range depending on the amount of the chain transfer agent used during the polymerization. As the chain transfer agent for controlling the molecular weight, for example, a low molecular weight linear acetal such as methylal and other conventionally known chain transfer agents in the (co) polymerization of trioxane can be used. If the molecular weight is too small, physical properties such as mechanical strength are not preferable. However, it is possible to supplement these physical properties by blending with an appropriate amount of unmodified high degree of polymerization polyoxymethylene, and especially when the modified POM copolymer of the present invention is used in a small amount as a compatibilizer, the molecular weight is Is effective even if it is relatively low, and there is no problem. On the other hand, if the molecular weight is too large, the fluidity and molding processability are deteriorated, which is not preferable.

The copolymerization method of the present invention can be carried out by the same equipment and method as the conventionally known copolymerization method of trioxane. That is, both batch type and continuous type are possible,
Although any of solution polymerization and melt bulk polymerization may be used, a continuous bulk polymerization method in which a liquid monomer is used and a solid powder mass polymer is obtained as the polymerization progresses is industrially common and preferable. In this case, an inert liquid medium can coexist as necessary.

As the polymerization apparatus used in the present invention, a cokneader, a twin-screw type continuous extrusion mixer, a twin-screw paddle type continuous mixer, and other trioxane continuous polymerization apparatuses which have been proposed so far can be used. It may be divided into two or more stages. In particular, those having a crushing function such that a solid polymer produced by the polymerization reaction can be obtained in a fine form are preferable.

The crude polymer which has been polymerized and discharged from the polymerization machine must be immediately mixed with and brought into contact with a deactivator to deactivate the polymerization catalyst. Examples of the deactivator for deactivating the polymerization catalyst in the present invention include ammonia, amines such as triethylamine, tributylamine and hindered amine, or alkali metal, alkaline earth metal hydroxides, salts and other known catalyst deactivators. Activators are used. These deactivators are preferably dissolved in water or an organic solvent such as cyclohexane, benzene or toluene in a cooling medium for the reaction product and contacted with the catalyst at the same time as cooling the polymer to be neutralized. It is particularly preferable to add it as an aqueous solution. Further, at this time, it is preferable to pulverize and process as fine powder, if necessary. The copolymer in which the polymerization catalyst has been deactivated in the present invention is further subjected to separation and recovery of unreacted monomer, washing, drying, etc., if necessary, and further, if necessary, through a stabilization step, and various stability. Add additives such as agents and melt-knead to pelletize the product.

The modified polyoxymethylene copolymer of the present invention is not only useful by itself, but also improved in sliding property even when used in combination with other generally known unmodified POM polymer or copolymer. It is also suitable as a composition which is effective and melt-kneaded with a general thermoplastic resin other than POM. Further, the modified POM copolymer of the present invention is also effective as a compatibilizing agent for a general unmodified POM polymer or copolymer with other thermoplastic resins and other additives. Here, as the other thermoplastic resin, for example, a polyolefin resin, a polyester resin, a polyamide resin, a polystyrene resin, a polyacrylic resin, a polyurethane resin, a fluororesin, etc. may be mentioned, and they are selectively used depending on the purpose. can do. A polyolefin resin is particularly preferable.
When the modified polyoxymethylene copolymer of the present invention is used in combination with a general unmodified POM (co) polymer and / or another thermoplastic resin, at least 2% by weight or more of the resin component must be present. It is preferably 5% by weight or more, more preferably 10% by weight or more. If it is too small, the effects of slidability, compatibility, etc., which are the objects of the present invention, cannot be obtained, which is not preferable. The blending amount of the thermoplastic resin other than the polyoxymethylene resin is 50% by weight or less, particularly preferably 30% by weight or less. If this is too large, the original properties of the polyoxymethylene resin are lost, and the compatibility is impaired, which is not preferable.

Further, in order to impart desired properties to the modified polyoxymethylene resin of the present invention or its composition,
Conventionally known additives, for example, various stabilizers such as antioxidants, heat stabilizers, weathering (light) stabilizers, hydrolysis stabilizers, lubricants, lubricants, nucleating agents, coloring agents such as dyes and pigments, mold release Additives such as agents, antistatic agents, plasticizers, flame retardants and the like may be added. Also,
Glass fibers, carbon fibers, other inorganic or organic fibrous reinforcing materials, glass beads, powder particles such as glass flakes,
A plate-shaped filler can also be appropriately mixed.

The polyoxymethylene resin composition can be prepared by various known methods. The necessary components are mixed, heated and melted, and kneaded. Specifically, a method in which necessary components are uniformly mixed with a tumbler or a mixer such as a Henschel mixer, and then the mixture is supplied to a uniaxial or biaxial extruder and melt-kneaded is generally used. You may use a roll, a Banbury mixer, a kneader, etc. It is preferable to dry each component in advance before kneading. The modified polyoxymethylene copolymer resin composition prepared by these methods may be once pelletized and then subjected to molding, or may be directly molded.

[0020]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited to these examples. In addition, the measuring method of the characteristic value
The evaluation method is as follows. [Weight average molecular weight] It was determined by gel permeation chromatography (LALLS) method. [Introduced Amount of Formula (1) Unit] It was determined by ¹ H-NMR from the integrated value of the peak based on the unit of Formula (1). [Friction coefficient] Mold a ring-shaped molded product with an injection molding machine,
The thrust type friction and wear test (Suzuki type) was performed under the following conditions. Counterpart material: Metal (S55C) Surface pressure: 7 kgf / cm Velocity: 30 cm / sec Examples 1 to 9 and Comparative Example 1 A jacket having a cross section in which two circles partially overlap and a heat (cold) medium is passed to the outside. Using a continuous mixing reactor equipped with a barrel with a barrel and two rotating shafts with a number of paddles for stirring and propelling in the longitudinal direction, hot water at 70 ° C is passed through the jacket and two rotations are performed. The shaft was rotated at a constant speed, and trioxane containing a comonomer shown in Table 1 and optionally methylal (a molecular weight modifier) was continuously supplied to one end of the shaft, and at the same time, boron trifluoride butyl etherate was added to the same position. Was dissolved in cyclohexane at a concentration of 1% to continuously add BF ₃ of 40 ppm to all the monomers to carry out copolymerization. Next, an aqueous solution containing triethylamine (room temperature, 0.1 wt% concentration) was added to the reaction product discharged from the discharge port of the polymerization machine, and at the same time, finely pulverized through a pulverizer and stirred at 60 ° C. for 30 minutes.
Then, the liquid is separated, washed and dried, and then tetrakis- [methylene-3- (3,5-di-t-butyl-4) is used as a stabilizer.
-Hydroxyphenyl) propionate] methane 0.5%
And melamine 0.2% were added, and the mixture was stirred and mixed in a Henschel mixer for 5 minutes, then melt-kneaded at a temperature of 210 ° C. using a vented twin-screw extruder and extruded to form pellets. The molecular weight of the produced copolymer and the content of the copolymer component of the formula (1) were measured, and the friction coefficient of the molded article obtained by injection molding the pellet was also measured. The properties and friction coefficient of the produced polymer are shown in Table 1. Also, for comparison, the same operation was performed when the comonomer A was not used. The results are shown in Table 1.

[0021]

[Table 1]

Examples 10-11, Comparative Example 2 As shown in Table 2, the modified POM obtained in Example 1 or 7 above.
The copolymer pellets and the unmodified POM copolymer pellet obtained in Comparative Example 1 were mixed and melt-extruded to prepare a mixture pellet, and a test piece was prepared by injection molding to measure the friction coefficient. Table 2 shows the results.

[0023]

[Table 2]

Examples 12-14, Comparative Example 3 As shown in Table 3, the modified POMs obtained in Examples 1 or 7 above.
To the copolymer pellets, the unmodified POM copolymer pellets obtained in Comparative Example 1, or a mixture of these pellets, low density polyethylene (PE) is further added and melt-kneaded and extruded under a certain condition to prepare a composition pellet. The cross section of the injection-molded molded product was observed with an electron microscope to examine the dispersed state of PE (the state of the interface, the size of dispersed particles, etc.). Further, an adhesive tape was attached to the surface of the molded product, and the peeling condition was observed due to poor dispersion when peeled off under certain conditions. The relative results are shown in Table 3.

[0025]

[Table 3]

[0026]

As is clear from the above description and examples, the modified POM copolymer of the present invention has excellent frictional properties by itself, and is a general unmodified POM polymer or copolymer. It has the effect of improving its frictional properties by being blended with, and also has a high affinity with other thermoplastic resins and additive substances, and has a better dispersibility than conventional unmodified POM polymers. It is also effective as a compatibilizer for improving the compatibility and dispersibility of ordinary unmodified POM with other thermoplastic resins.

Claims (6)

[Claims] 1. An oxyalkylene group containing an oxymethylene group (—CH ₂ —O—) as a main repeating unit and containing a copolymerized unit represented by the following general formula (1) in an amount of 0.01 to 10 mol% based on the oxymethylene unit. unit _{(- (CH 2) n -O} -) ( the number of carbon atoms n of the alkylene 2-4) comprises 0 to 10 mol% with respect to the oxymethylene units as copolymerized units, the weight average molecular weight of from 2,000 to 400,000 Is a modified polyoxymethylene copolymer. Embedded image (However, -R represents an aliphatic hydrocarbon having 5 or more carbon atoms) 2. Trioxane as a main monomer, vinyl ether (comonomer A) represented by the following general formula (2) with respect to trioxane in an amount of 0.03 to 30 mol%, and cyclic ether or cyclic formal (comonomer B) into trioxane. On the other hand, a method for producing a modified polyoxymethylene copolymer, characterized by using 0 to 30 mol% and copolymerizing in the presence of a cationic active catalyst. CH ₂ = CH-OR (2) (However, -R represents an aliphatic hydrocarbon having 5 or more carbon atoms.) 3. The cyclic ether or cyclic formal (comonomer B) is ethylene oxide, propylene oxide, oxetane, 1,3-dioxolane, 1,3-dioxane, 1,4-butanediol formal, diethylene glycol formal, 1,3. The method for producing a modified polyoxymethylene copolymer according to claim 2, which is one or more of 6,6-trioxocane. 4. An unmodified polyoxymethylene (co) polymer containing the modified polyoxymethylene copolymer according to claim 1 in an amount of 2% by weight or more based on all resin components and the balance not containing a copolymerized unit of the formula (1). A modified polyoxymethylene copolymer composition which is a coalescence and / or less than 50% by weight of another thermoplastic resin. 5. The modified polyoxymethylene copolymer composition according to claim 4, which contains at least 5% by weight of the modified polyoxymethylene copolymer according to claim 1. 6. The modified polyoxymethylene copolymer composition according to claim 4, wherein the other thermoplastic resin is a polyolefin resin.