JP7061479B2 - Polyacetal copolymer and its polymerization method - Google Patents

Description

The present invention relates to a polyacetal copolymer having high rigidity, excellent creep characteristics and sliding characteristics, and an extremely small amount of formaldehyde generated, and a polymerization method thereof.

Polyacetal resin has excellent mechanical properties, thermal properties, electrical properties, slidability, moldability, etc., and is mainly used as structural materials and mechanical parts for electrical equipment, automobile parts, precision machinery, etc. Widely used for parts, etc. However, with the expansion of fields in which polyacetal resins are used, the required characteristics tend to become more sophisticated, complex, and specialized. As such required characteristics, it is required to further improve the rigidity and suppress the generation of formaldehyde while maintaining the excellent slidability and appearance inherent in the polyacetal resin.

On the other hand, for the purpose of simply improving the rigidity, a method of filling a polyacetal resin with a fibrous filler or the like is generally used, but in this method, the appearance of the molded product is poor due to the filling of the fibrous filler or the like. There are problems such as deterioration of sliding characteristics and toughness.

Further, it is known that the polyacetal copolymer improves the rigidity without substantially impairing the slidability and appearance by reducing the amount of comonomer, but the toughness is lowered in the method of reducing the amount of comonomer. Not only that, but also the thermal stability of the polymer is lowered, which causes problems, and it is not always possible to meet the demand.
Attempts have been made to improve the rigidity by introducing a branched structure, but depending on the type of comonomer, when a cationic polymerization catalyst, especially a protonic acid, is used as the polymerization catalyst, the start of polymerization may be delayed and the polymerization may suddenly occur explosively. There was also a problem in terms of production stability.

For example, with respect to a polyacetal copolymer, a copolymer obtained by copolymerizing a trioxane with a compound having two or more glycidyl ether groups in one molecule has been proposed (Patent Document 1). However, when a compound having a plurality of epoxy groups represented by glycidyl ether groups and ether oxygen as functional groups is used for polymerization, there remains a problem in polymerization stability. In particular, when protonic acid is used as a polymerization catalyst, polymerization does not occur at a low catalytic amount, and if the amount of catalyst is increased, a phenomenon occurs in which a violent polymerization reaction suddenly occurs after an irregular induction period, making polymerization control difficult. ing.

JP 2001-163944

Suppressing the generation of formaldehyde in polyacetal copolymers is an ongoing challenge, but the demands are increasing year by year.

An object of the present invention is to provide a polyacetal copolymer having excellent thermal stability such as production stability and formaldehyde generation while maintaining the levels of rigidity, creep characteristics and sliding characteristics by introducing a branched structure as described above. The purpose is to provide a polymerization method.

Ｐは０～２０の整数を表す。
３． トリオキサン、炭素数２以上のオキシアルキレン基を環内に有する環状アセタール化合物および１分子中にエポキシ基を２個以上有しエポキシ基以外は炭化水素からなるポリエポキシ化合物、とをカチオン重合触媒の存在下、共重合させるポリアセタール共重合体の重合方法。
４． 前記ポリエポキシ化合物が、下記式で表されるポリエポキシ化合物である前記３記載のポリアセタール共重合体の重合方法。

Ｐは０～２０の整数を表す。
５． 前記カチオン重合触媒が、プロトン酸である前記３または４記載のポリアセタール共重合体の重合方法。 The object of the present invention was achieved by the following.
1. 1. A polyacetal obtained by copolymerizing a trioxane, a cyclic acetal compound having an oxyalkylene group having 2 or more carbon atoms in a ring, and a polyepoxide compound having two or more epoxy groups in one molecule and consisting of a hydrocarbon other than the epoxy group. Copolymer.
2. 2. The polyacetal copolymer according to 1 above, wherein the polyepoxy compound is a polyepoxy compound represented by the following formula.

P represents an integer from 0 to 20.
3. 3. Presence of a cationic polymerization catalyst of trioxane, a cyclic acetal compound having an oxyalkylene group having 2 or more carbon atoms in a ring, and a polyepoxide compound having two or more epoxy groups in one molecule and consisting of a hydrocarbon other than the epoxy group. Below, a method for polymerizing a polyacetal copolymer to be copolymerized.
4. The method for polymerizing a polyacetal copolymer according to 3 above, wherein the polyepoxy compound is a polyepoxy compound represented by the following formula.

P represents an integer from 0 to 20.
5. 3. The method for polymerizing a polyacetal copolymer according to 3 or 4, wherein the cationic polymerization catalyst is a protonic acid.

According to the present invention, it is possible to provide a polyacetal copolymer and a polymerization method having excellent thermal stability such as production stability and formaldehyde generation while maintaining the levels of rigidity, creep characteristics and sliding characteristics. ..

Hereinafter, specific embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments, and the present invention is carried out with appropriate modifications within the scope of the object of the present invention. can do.

<Polyacetal copolymer>
The polyacetal copolymer of the present invention is a trioxane, a cyclic acetal compound having an oxyalkylene group having 2 or more carbon atoms in a ring, and a polyepoxide having two or more epoxy groups in one molecule and consisting of a hydrocarbon except for the epoxy group. It is characterized by being a polyacetal copolymer obtained by copolymerizing with a compound.

≪Trioxan≫
The trioxane 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 is used by purifying it by a method such as distillation. ..

<< Cyclic acetal compound having an oxyethylene group having 2 or more carbon atoms in the ring (hereinafter, also referred to as component (A)) >>
The cyclic acetal compound having an oxyethylene group having 2 or more carbon atoms in the ring of the present invention is a compound generally used as a comonomer in the production of a polyacetal copolymer, specifically, 1,3-dioxolane. Examples thereof include 1,3,6-trioxocan, 1,4-butanediol formal and the like.

In the present invention, the component (A) is preferably used in the range of 0.01 to 20 parts by mass, more preferably 0.05 to 5 parts by mass with respect to 100 parts by mass of trioxane. ..

<< A polyepoxy compound having two or more epoxy groups in one molecule and consisting of hydrocarbons other than the epoxy group (hereinafter, also referred to as component (B)) >>
The component (B) used in the present invention is characterized by having two or more epoxy groups in one molecule and being a polyepoxy compound composed of a hydrocarbon other than the epoxy group.

Generally, when an epoxy group is introduced into a molecule, it is often introduced in the structure of a glycidyl ether group using epichlorohydrin as a raw material, but the epoxy group of the present invention is characterized by having an epoxy group that is not derived from the glycidyl ether group. do.
The glycidyl ether group of the present invention refers to a group having the following structure. * Represents a binding site with another structure.

It is known as a well-known technique that an epoxy compound having an epoxy group derived only from a diglycidyl ether group is used as a comonomer, but in the present invention, the absence of a glycidyl ether group maintains the strength of the polyacetal copolymer. However, it was found that the amount of formaldehyde generated can be suppressed.

Specifically, 1,3-butadiene die epoxide (B-5 below), 1,4-pentadiene epoxide, 1,5-hexadiene epoxide (B-4 below), 1,6-peptadiene epoxide, 1,7-octadiene epoxide (B-3 below), 1,8-nonadiene epoxide, 1,9-decadiene epoxide (B-2 below), 1,10-undecadiene epoxide, 1, 11-dodecadie epoxide (B-1 below) and the like can be mentioned.

好ましくは、下記一般式１，２で表されるエポキシ化合物である。
式１

式２

Ｐは、０～２０の整数、ｎは，０～１０の整数、ｍは、１～１０の整数を表す。

It is preferably an epoxy compound represented by the following general formulas 1 and 2.
Equation 1

Equation 2

P represents an integer of 0 to 20, n represents an integer of 0 to 10, and m represents an integer of 1 to 10.

In the present invention, the component (B) is preferably used in the range of 0.01 to 5 parts by mass, more preferably 0.03 to 1 part by mass with respect to 100 parts by mass of trioxane. ..

<Polymerization method of polyacetal copolymer>
The method for polymerizing the polyacetal copolymer of the present invention is from trioxane, a cyclic acetal compound having an oxyalkylene group having 2 or more carbon atoms in a ring, and a hydrocarbon having two or more epoxy groups in one molecule, except for the epoxy group. It is characterized in that the polyepoxide compound obtained from the above is copolymerized in the presence of a cationic polymerization catalyst.

<Cationic polymerization catalyst>
As the cationic polymerization catalyst, a polymerization catalyst known in cationic copolymerization using trioxane as a main monomer can be used. Typical examples include Lewis acid and protonic acid. In particular, it is preferably a protonic acid.

≪Protonic acid≫
Examples of the protonic acid include perfluoroalkanesulfonic acid, heteropolyacid, isopolyacid and the like.
Specific examples of perfluoroalkane sulfonic acid include trifluoromethanesulfonic acid, pentafluoroethanesulfonic acid, heptafluoropropanesulfonic acid, nonafluorobutanesulfonic acid, undecafluoropentanesulfonic acid, tridecafluorohexanesulfonic acid, and pentadecafluoro. Examples thereof include heptane sulfonic acid and heptadecafluorooctane sulfonic acid.

Heteropolyacids are polyacids produced by dehydration condensation of different types of oxygen acids, and are mononuclear or polynuclear formed by the presence of a specific different element in the center and the condensation of condensed acid groups sharing oxygen atoms. Has complex ions. The isopolyacid is also referred to as an isopolyxic acid, a homonuclear condensed acid, or an allogeneic multiplex acid, and refers to a high molecular weight inorganic oxygen acid composed of a condensate of an inorganic oxygen acid having a single kind of metal having a V valence or a VI valence. ..

Specific examples of heteropolyacids include phosphomolybdic acid, phosphotungstic acid, phosphotungstic acid, phosphoribdovanadic acid, phosphoribdotangustovanadic acid, lintangustvanadic acid, keitungstic acid, silicate molybdenate, and keimolibd. Examples thereof include tungstic acid, tungstic acid and tungstic acid. In particular, from the viewpoint of polymerization activity, the heteropolyacid is preferably selected from silicomolybdic acid, silicotungstic acid, phosphomolybdic acid, and phosphotungstic acid.

Specific examples of isopolyacids include isopolytungstic acid exemplified by paratungstic acid, metatungstic acid, paramolybdic acid, isopolymolybdic acid exemplified by metamolybdic acid, metapolyvanadium acid, and isopolyvanadium acid. And so on. Above all, isopolytungstic acid is preferable from the viewpoint of polymerization activity.

≪Lewis acid≫
Examples of Lewis acid include halides of boron, tin, titanium, phosphorus, arsenic and antimony, and specific examples thereof include boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentafluoride and phosphorus pentafluoride. , Antimony pentafluoride and its complex compounds or salts.

The amount of the polymerization catalyst is not particularly limited, but is preferably 0.1 ppm or more and 50 ppm or less, and more preferably 0.1 ppm or more and 30 ppm or less with respect to the total of all the monomers. Particularly preferably, it is 0.1 ppm or more and 10 ppm or less.

In the production of the polyacetal copolymer of the present invention, the amount of terminal groups can be adjusted by using a component for adjusting the molecular weight in combination with the above-mentioned components. Examples of the component for adjusting the molecular weight include a chain transfer agent that does not form an unstable terminal, that is, a compound having an alkoxy group such as methylal, monomethoxymethylal, and dimethoxymethylal.

The method for polymerizing the polyacetal copolymer of the present invention is not particularly limited. The polymerization apparatus is not particularly limited in the production, and a known apparatus is used, and any method such as a batch type or a continuous type is possible. Further, it is preferable to keep the polymerization temperature at 65 ° C. or higher and 135 ° C. or lower.

The cationic polymerization catalyst is preferably diluted with an inert solvent that does not adversely affect the polymerization.

The deactivation of the polymerization catalyst after the polymerization can be carried out by a conventionally known method. For example, after the polymerization reaction, a basic compound or an aqueous solution thereof may be added to the product reaction product discharged from the polymerization machine or the reaction product in the polymerization machine.

The basic compound for neutralizing and inactivating the polymerization catalyst is not particularly limited. After polymerization and deactivation, if necessary, further washing, separation and recovery of unreacted monomers, drying and the like are carried out by conventionally known methods.

The polyacetal copolymer obtained as described above preferably has a weight average molecular weight of 10,000 to 500,000, and particularly preferably 20,000 to 150,000. Regarding the terminal group, the amount of hemiformal detected by ¹ H-NMR is preferably 0 to 4 mol / kg, and particularly preferably 0 to 2 mmol / kg.

In order to control the amount of hemiformal terminal groups within the above range, the amount of impurities, particularly water content, in the total amount of monomers and comonomer to be polymerized is preferably 20 ppm or less, and particularly preferably 10 ppm or less.

Further, the polyacetal copolymer of the present invention may contain, if necessary, general additives for thermoplastic resins such as dyes, colorants such as pigments, lubricants, nucleating agents, mold release agents, antistatic agents, and surfactants. One or two or more kinds of activators, organic polymer materials, inorganic or organic fibrous, powdery, plate-like fillers and the like can be added.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.
<Polymerization reaction>
Put 300 g of trioxane in a closed autoclave having a jacket through which a heat medium can pass and a stirring blade, and further add 1,3-dioxolane (DO) as the component (A) and the compounds shown in Table 1 as the component (B). , Each was added in proportions of parts by mass shown in Table 1. After stirring these contents and keeping the internal temperature at about 80 ° C by passing hot water at 80 ° C through the jacket, the catalytic solution (heteropoly acid is a solution of methyl formate, trifluoromethanesulfonic acid, boron trifluorodibutyletherate is cyclohexane). The solution) was added so as to have the catalyst concentration (to all monomers) shown in Table 1, and the polymerization was started.

After 5 minutes, 300 g of water containing 0.1% triethylamine was added to this autoclave to stop the reaction, the contents were taken out, pulverized to 200 mesh or less, washed with acetone and dried, and then the polyacetal copolymer yield (to all the added monomers). The ratio (%) of the obtained copolymer was calculated. The results are shown in Table 1.

For comparison, a polyacetal copolymer using the following diglycidyl compound (having two glycidyl ether groups) in place of the component (B) of the present invention was polymerized to obtain a comparative polyacetal copolymer.

To 100 parts by mass of the polyacetal copolymer obtained by the above method, 0.3 parts by mass of pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] was added as a stabilizer. , And 0.15 parts by mass of melamine were melt-kneaded at 210 ° C. in a small twin-screw extruder to obtain a pellet-shaped polyacetal resin composition.
The following evaluation was performed using this pellet.

<Thermal stability>
[Amount of formaldehyde generated from the melt]
After accurately weighing 5 g of pellets and holding in a metal container at 200 ° C. for 5 minutes, the atmosphere in the container is absorbed into distilled water. The amount of formaldehyde in this aqueous solution is referred to as JIS K0102, 29. The amount of formaldehyde gas (ppm) generated from the pellets was calculated by quantifying according to (formaldehyde section). The results are shown in Table 1.

In Examples 1 to 8, it was clarified that the polyacetal copolymer was obtained in a high yield with a low catalyst amount, and the polyacetal copolymer having a small amount of formaldehyde and excellent thermal stability was obtained. In Comparative Examples 1, 3 and 5, no polymerization reaction was observed at a low catalytic amount.
In Comparative Examples 2 and 4, although the polymerization reaction occurred under the condition of a high catalytic amount, it became an extremely violent explosive reaction immediately after the cloudiness, and difficulty in controlling the reaction was observed.

The yield of the obtained polyacetal copolymer was lower than that of the examples, and the amount of formaldehyde generated was also high. In Comparative Example 6, the yield was slightly lower and the amount of formaldehyde generated was higher than that in Example 8.

As is clear from the results in Table 1, according to the present invention, it is possible to provide a polyacetal copolymer and a polymerization method having excellent thermal stability such as production stability and the amount of formaldehyde generated.

Claims (5)

For 100 parts by mass of trioxane, 0.01 to 20 parts by mass of a cyclic acetal compound having an oxyalkylene group having 2 or more carbon atoms in the ring, and hydrocarbons other than the epoxy group having two or more epoxy groups in one molecule. A polyacetal copolymer obtained by copolymerizing 0.05 to 5 parts by mass of a polyepoxide compound composed of the above.
A polyacetal copolymer in which the cyclic acetal compound is selected from 1,3-dioxolane, 1,3,6-trioxocan and 1,4-butanediol formal . The polyacetal copolymer according to claim 1, wherein the polyepoxy compound is a polyepoxy compound represented by the following formula.

P represents an integer from 0 to 20. 0.01 to 20 parts by mass of a cyclic acetal compound having an oxyalkylene group having 2 or more carbon atoms in the ring with respect to 100 parts by mass of trioxane, and hydrocarbons other than the epoxy group having two or more epoxy groups in one molecule. A method for polymerizing a polyacetal copolymer in which 0.05 to 5 parts by mass of a polyepoxide compound composed of the above is copolymerized in the presence of a cationic polymerization catalyst.
A method for polymerizing a polyacetal copolymer, wherein the cyclic acetal compound is selected from 1,3-dioxolane, 1,3,6-trioxocan and 1,4-butanediol formal . The method for polymerizing a polyacetal copolymer according to claim 3, wherein the polyepoxy compound is a polyepoxy compound represented by the following formula.

P represents an integer from 0 to 20. The method for polymerizing a polyacetal copolymer according to claim 3 or 4, wherein the cationic polymerization catalyst is a protonic acid.