JPH0681800B2 - Manufacturing method of polyacetal with excellent impact resistance - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a polyacetal having excellent impact resistance.

More specifically, the present invention provides excellent impact resistance by homopolymerizing formaldehyde or trioxane or copolymerizing formaldehyde or trioxane in the presence of a multiphase interpolymer having an epoxy group in the outermost phase. The present invention relates to a method for producing polyacetal.

(Prior Art) Since polyacetal has excellent mechanical properties, fatigue properties, and friction and wear properties, the demand for engineering plastics tends to increase more and more in recent years.

However, polyacetal has a drawback that it has a low impact resistance, for example, a low notched Izod value, and is easily broken in the presence of residual stress and small scratches during molding.

JP-A-59-136343 discloses that polyoxymethylene has a 2
It is disclosed that a composition obtained by adding an acrylic multiphase interpolymer having a layered structure and a particle size of 10 to 100 μm has excellent impact resistance. However, the composition obtained by the method of the present publication has a drawback that impact resistance in a certain direction is significantly reduced depending on processing conditions. In addition, the range of improvement in impact resistance is not great.

Specifically, during processing such as injection molding, extrusion molding, blow molding, etc., processing conditions such that the dispersed multiphase interpolymers are oriented, for example, the molten resin in the injection molded product mold. In the weld portion formed by joining, the impact resistance of the molded product in a certain direction is significantly reduced, that is, the weld strength is reduced. These phenomena show that the multi-phase interpolymer dispersed in polyoxymethylene does not show a uniform dispersion state at all locations of the molded product, and that dispersion or non-uniformity in the molded product such as aggregation or orientation occurs. It occurs because it occurs.

Therefore, it is not possible to obtain a composition having excellent impact resistance by the method of this publication.

Further, in JP-A-62-36451, a composition is obtained by adding an acrylic multiphase interpolymer having a particle size of 10 to 100 μm and having a two-phase structure and a thermoplastic polyurethane to polyoxymethylene. It discloses that the impact resistance of the article is improved. However, even in this invention, a composition having excellent impact resistance cannot be obtained.

On the other hand, Japanese Patent Publication No. 57-10128 discloses that an oxymethylene copolymer and an organic polymer having active hydrogen such as polyurethane are bound by a polyfunctional coupling agent in the presence of formaldehyde, It is disclosed to improve impact performance. The method of the present disclosure is a method of utilizing the reactivity between the active hydrogen at the polymer terminal and the coupling agent, but the active hydrogen at the polymer terminal is extremely small, and the reaction with the coupling agent is extremely difficult. is there. As a result, this method often yields only a mixture of an oxymethylene copolymer and an organic polymer having active hydrogen such as polyurethane.

(Problems to be Solved by the Invention) An object of the present invention is to overcome the problems in the prior art as described above, while maintaining the excellent properties of polyacetal,
It is to provide a method for producing a polyacetal having excellent impact resistance.

(Means for Solving the Problem) As a result of intensive investigations by the present inventors, the polyacetal obtained by the present invention has extremely high impact resistance without impairing the inherent properties of the polyacetal. I found out that

That is, the present invention is that formaldehyde or trioxane is used alone in the presence of a multiphase interpolymer having a multiphase structure of two or more phases composed of repeating soft phases and hard phases and having an epoxy group in the outermost phase thereof. The present invention relates to a method for producing a polyacetal excellent in impact resistance by polymerizing or copolymerizing formaldehyde or trioxane with a cyclic ether or cyclic formal.

The multi-phase interpolymer that can be used in the present invention is a multi-phase interpolymer having a multi-phase structure of two or more phases composed of repeating soft phase and hard phase, and having an epoxy group in the outermost phase thereof.

For example, a multi-phase interpolymer having a two-phase structure, a first phase having an elastomer phase that is a soft phase, a second phase having a hard phase, and an outermost hard phase having an epoxy group is used. It can be used in the invention.

The glass transition temperature (hereinafter abbreviated as Tg) of the polymer constituting the soft phase is preferably less than 25 ° C, more preferably less than 0 ° C. The Tg of the polymer constituting the hard phase is preferably 25 ° C or higher, more preferably 50 ° C or higher.

The soft phase and the hard phase of the multiphase interpolymer are composed of a homopolymer composed of the following monomers or a copolymer composed of two or more kinds of monomers.

Examples of usable monomers include styrene and p-
Aromatic vinyl monomers such as methylstyrene and α-methylstyrene; vinyl halide monomers such as vinyl chloride and vinylidene chloride; nitrile monomers such as acrylonitrile and methacrylonitrile; methyl methacrylate, butyl methacrylate, hydroxyethyl methacrylate, etc. Methacrylic acid ester of methyl acrylate, ethyl acrylate, n-butyl acrylate, acrylic acid 2
-Acrylic esters such as ethylhexyl and hydroxyethyl acrylate; vinyl esters such as vinyl acetate and vinyl propionate; unsaturated amides such as acrylamide and methacrylamide; vinyl alkyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether, etc. Can be mentioned.

Further, a conjugated diene such as butadiene or isoprene may be added to these vinyl-polymerizable monomers for copolymerization, or a homopolymer of these conjugated dienes may be used.

The soft phase of the multi-phase interpolymer is preferably a polymer composed of an acrylic ester or a conjugated diene, and more preferably a polymer composed of n-butyl acrylate, 2-ethylhexyl acrylate, or styrene-butadiene. preferable.

The hard phase of the multi-phase interpolymer is preferably a polymer composed of methacrylic acid ester, aromatic vinyl, or vinyl halide, and further, methyl methacrylate,
Alternatively, a polymer composed of styrene or vinyl chloride is more preferable.

As a preferable combination of polymers constituting the hard phase and the soft phase in the multiphase interpolymer, for example, the hard phase is a polymer containing methyl methacrylate as a main component, and the soft phase is mainly n-butyl acrylate. Polymer as a component; a polymer having a hard phase as a main component of methyl methacrylate,
And a soft phase is a polymer whose main component is 2-ethylhexyl acrylate; a hard phase is a polymer whose main component is methyl methacrylate,
And a soft phase is a copolymer whose main component is styrene-butadiene; A hard phase is a polymer whose main component is styrene, and a soft phase is a copolymer whose main component is styrene-butadiene; A hard phase is vinyl chloride A copolymer containing styrene-butadiene as a main component and a soft phase containing styrene-butadiene as a main component; a hard phase containing acrylonitrile as a main component and a soft phase containing styrene-butadiene as a main component There are polymers, etc.

The most preferred combination of multiphase interpolymers is
The hard phase of the multi-phase interpolymer is composed of a homopolymer of methyl methacrylate or a copolymer composed of 80% by weight or more of methyl methacrylate and 20% by weight or less of another copolymerizable monomer, and is soft. Phase is n-butyl acrylate homopolymer, or n-butyl acrylate 80% by weight
In addition to the above, there is a multiphase interpolymer composed of a copolymer containing 20% by weight or less of another copolymerizable monomer.

Further, the outermost phase of these multiphase interpolymers needs to have an epoxy group. When a multiphase interpolymer composed of a soft phase and a hard phase and having no epoxy group in the outermost phase is used, a significant improvement in impact resistance cannot be achieved. On the other hand, when a multiphase interpolymer comprising a soft phase and a hard phase is repeated and the outermost phase has an epoxy group, impact resistance is dramatically improved.

The multiphase interpolymer in the present invention can be produced using the polymerization technique shown below. As a specific example, a method for producing a multiphase interpolymer having a two-layer structure, having a soft phase in the first phase, a hard phase in the second phase, and an epoxy group in the outermost phase will be shown.

Into water containing additives necessary for emulsion polymerization, such as an emulsifier,
Polymerization is carried out while adding a monomer and a polymerization initiator necessary for forming a soft phase while stirring.

As the emulsifier, an alkyl sulfosuccinate such as sodium dioctyl sulfosuccinate and an alkyl aromatic sulfonate such as sodium dodecylbenzene sulfonate can be used.

As the polymerization initiator, peroxides such as diisopropylbenzene hydroperoxide and benzoyl peroxide; azo compounds such as azobisisobutyronitrile and the like can be used.

In order to impart appropriate elasticity to the soft phase, it is preferable to copolymerize the monomer constituting the soft phase and the polyfunctional crosslinking agent.

As the polyfunctional crosslinking agent, commonly used crosslinking agents such as divinyl compounds, diallyl compounds, diacrylic compounds, diethylene glycol diacrylate, and dimethacrylic compounds can be used, and ethyl diacrylate and n-butyl diacrylate are preferable. The amount of the polyfunctional crosslinking agent added is preferably 0.1 to 5.0% by weight, and more preferably 0.1 to 2.5% by weight, based on the total weight of the polymer constituting the elastomer phase.

Furthermore, it is preferred to use multifunctional grafting agents to effect the chemical bonding between the hard and soft phases. Examples of the polyfunctional grafting agent include polyfunctional monomers having different functionalities, for example, allyl esters of acrylic acid, methacrylic acid, maleic acid, fumaric acid and the like, and allyl acrylate and allyl methacrylate are preferable. The amount of the polyfunctional grafting agent added is 0.1 to, based on the total weight of the polymer constituting the soft phase, that is, the phase serving as the graft base.
5.0 wt% is preferable, and 0.1 to 2.5 wt% is more preferable.

At the time when the polymerization reaction forming the soft phase is completed, next, the monomer forming the hard phase and the vinyl monomer having an epoxy group are added. At this time, if necessary, a polymerization initiator can be added additionally.

Emulsion polymerization is usually performed at a temperature of 50 to 90 ° C.

The multiphase polymer obtained by the emulsion polymerization can be separated from water while maintaining the particle form by using a conventional means such as salting out, freeze-thawing, or spray drying. For salting out, an electrolyte solution such as aluminum chloride or sodium chloride is used, and the precipitate is filtered off. Further, the multiphase polymer referred to in the present invention can be obtained through washing and drying steps.

In addition, a novel intermediate phase having a different monomer composition may be introduced between each phase constituting the multiphase polymer, that is, between the hard phase and the soft phase.

For example, a hard phase containing styrene as a main component can be introduced as a novel intermediate phase between a soft phase containing n-butyl acrylate as a main component and a hard phase containing methyl methacrylate as a main component.

The outermost phase of the multiphase interpolymer that can be used in the present invention must have an epoxy group. The introduction of the epoxy group into the outermost phase is usually carried out by copolymerizing a monomer constituting the outermost phase and a vinyl monomer having an epoxy group. Examples of the vinyl monomer having an epoxy group include compounds such as p-glycidyl α-methylstyrene, glycidyl methacrylate, glycidyl ethyl acrylate, glycidyl ethyl methyl methacrylate, glycidyl vinyl ether, glycidyl acrylate, and P-glycidyl styrene. Further, the introduction of the epoxy group into the outermost phase is also carried out by reacting the functional group contained in the outermost phase with the functional group of the compound having both the epoxy group and the functional group.

Formaldehyde or trioxane is used in the homopolymerization of the present invention. In the copolymerization,
Formaldehyde or trioxane and cyclic ethers or formal are used.

Cyclic ethers used for copolymerization include ethylene oxide, propylene oxide, butylene oxide, epichlorohydrin, styrene oxide, oxetane, 3,3-bis (chloromethyl) oxetane, tetrahydrofuran,
There are oxepane etc. Among these cyclic ethers, ethylene oxide is particularly preferable.

The cyclic formal includes ethylene glycol formal, propylene glycol formal, diethylene glycol formal, triethylene glycol formal, 1,4-butanediol formal, 1,5-pentanediol formal, and 1,6-hexanediol formal. Among these cyclic formals, ethylene glycol formal, diethylene glycol formal and 1,4-butanediol formal are particularly preferable.

Cyclic ether, cyclic formal, formaldehyde,
0.03 to 100 parts by weight, more preferably 0.1 to 50 parts by weight is used with respect to 100 parts by weight of trioxane.

A cationic polymerization catalyst is used in the homopolymerization and copolymerization of the present invention.

Cationic polymerization catalysts include tin tetrachloride, tin tetrabromide, titanium tetrachloride, aluminum trichloride, zinc chloride, vanadium trichloride, antimony pentafluoride, boron trifluoride, boron trifluoride diethyl etherate, trifluoride. So-called Friedel compounds such as boron trifluoride coordination compounds such as boron fluoride acetic unhydrate and boron trifluoride triethylamine complex compounds
Kraft-type compounds, perchloric acid, acetyl perchlorate, inorganic acids and organic acids such as hydroxyacetic acid, trichloroacetic acid, p-toluenesulfonic acid, triethyloxonium tetrafluoroborate, triphenylmethylhexafluoroantimonate, allyldiazonium hexafluoro Examples thereof include complex salt compounds such as phosphate and allyldiazonium tetrafluoroborate, and alkyl metals such as diethylzinc, triethylaluminum and diethylaluminum chloride.

These cationic polymerization catalysts are used in the range of 0.0005 to 5 parts by weight with respect to 100 parts by weight of formaldehyde or trioxane. Homopolymerization or copolymerization is carried out without solvent or in an organic medium.

The organic medium that can be used in the present invention includes n
-Aliphatic hydrocarbons such as pentane, n-hexane, n-heptane, n-octane, cyclohexane and cyclopentane; aromatic hydrocarbons such as benzene, toluene and xylene; methylene chloride, chloroform, carbon tetrachloride, ethylene chloride, There are halogenated aliphatic hydrocarbons such as trichloroethylene; halogenated aromatic hydrocarbons such as chlorobenzene and o-dichlorobenzene. These organic media may be used alone or in combination of two or more.

The multiphase interpolymer is usually used by being dispersed in the reaction system. The multiphase interpolymer is usually used in the range of 0.5 to 150 parts with respect to 100 parts by weight of formaldehyde or lyoxa.

The polymerization temperature is usually set between −20 and 230 ° C., but it is more preferably between 20 and 210 ° C. in the case of using no solvent, and more preferably between −10 and 120 ° C. when using an organic medium. preferable.

The polymerization time is not particularly limited, but is set between 5 seconds and 300 minutes.

After a lapse of a predetermined time, a terminating agent is added to the reaction system to complete the polymerization. The obtained polymer is stabilized by removing the unstable end by hydrolysis or blocking the unstable end by a method such as esterification. The stabilized polyacetal is added with a stabilizer or the like for practical use.

Hereinafter, the present invention will be specifically described with reference to examples and comparative examples, but the present invention is not limited to these examples.

The measurement items in the examples are as follows.

Izod impact value (notched): Measured according to ASTM D-256.

MI: ASTM D-1238 ・ 57T E Condition: 190 ℃, 2.16kg
Measured by load.

Example 1 (1) A method for producing a multiphase interpolymer having an epoxy group in the outermost phase.

In a 10 beaker equipped with a stirrer and a condenser, 5.7 distilled water, 20 g of sodium dioctylsulfosuccinate as an emulsifier, and 1.2 g of Rongalit as a reducing agent are added and uniformly dissolved.

As the first soft phase, -n-butyl acrylate (hereinafter
BA, abbreviated) 1,270 g, styrene (hereinafter abbreviated as St) 320 g, diethylene glycol diacrylate (hereinafter abbreviated as DEGA) 20
g, allyl methacrylate (ALMA) 13 g, diisopropylbenzene hydroperoxide (hereinafter abbreviated as PBP)
1.6 g of homogeneous solution was added, and the mixture was polymerized at 80 ° C. The reaction was completed in about 40 minutes. The polymer obtained by polymerizing this product alone had a Tg of -38 ° C.

Next, MMA 680g, B as the second hard phase (outermost phase)
A4.0g, glycidyl methacrylate 12g, PBP0.6g, n
-Octyl mercaptan (hereinafter abbreviated as OM) 0.2 g homogeneous solution was added.

The molecular weight of the polymer obtained by polymerizing this product alone is 1,
220,000, Tg was 109 ℃. The reaction at this stage was completed in about 15 minutes.

The temperature was then raised to 95 ° C and held for 1 hour. The obtained polymer was put into a 0.5% aqueous solution of aluminum chloride to coagulate the polymer, washed with warm water 5 times, and dried to obtain a white floc-like multiphase interpolymer.

(2) A method for producing polyacetal.

After suspending 1060 gr of the multiphase interpolymer obtained in (1) in cyclohexane 10, anhydrous formaldehyde was added.
The polymerization catalyst, boron trifluoride dibutyl etherate, was introduced into cyclohexane continuously at 2000 gr / hr for 2 hours at 0.12 gr / hr. During this period, the polymerization temperature was maintained at 0 ° C. Then tributylamine 10gr in cyclohexane
Was added to stop the polymerization. After separating the polymer from cyclohexane, in a 30 mmφ single screw extruder,
Stabilized by adding 40% acetic anhydride. After adding a stabilizer to this polymer, it was kneaded and melted using a 30 mmφ twin-screw extruder to obtain pelletized polyacetal.

The MI of this polyacetal was 2.5 gr / 10 minutes, and the Izod impact value was 65 kg.cm/cm, and a polyacetal excellent in impact resistance was obtained.

Example 2 (3) A method for producing a multiphase interpolymer having an epoxy group in the outermost phase.

Instead of the glycidyl methacrylate used to form the hard phase in Example 1, glycidyl ethyl methacrylate: A multiphase interpolymer was obtained in the same manner as in Example 1 except that 13.5 gr was used and the reagents used in Example 1 were used.

(4) A method for producing polyacetal.

In the cyclohexane which is the inner liquid of the polymerization reactor (3)
The polyphase interpolymer obtained in Step 3 was 350 gr / hr, anhydrous formaldehyde was 2500 gr / hr, ethylene glycol formal was 120 gr / hr, titanium tetrachloride was 0.15 gr / hr, methylal was 13 gr / hr, and cyclohexane was 10 kg / hr. It was continuously supplied for an hour. The polymerization temperature was maintained at 15 ° C during this period.

The internal liquid containing the polymer was withdrawn from the polymerization reactor so that the liquid surface was kept constant, transferred to a container containing tributylamine, and the polymerization was stopped. The polymer was separated from cyclohexane and stabilized by the addition of 3% triethylamine in a 50 mmφ single screw extruder. After adding a stabilizer to this polymer, it was pelletized using a 45 mmφ twin-screw extruder.

The MI of this polyacetal was 9.0 gr / 10 minutes, the Izod impact value was 55 kg.cm/cm, and polyacetal excellent in impact resistance was obtained.

Example 3 (5) A method for producing a multiphase interpolymer having an epoxy group in the outermost phase.

In place of the styrene used for forming the soft phase in Example 1, α-
The same procedure as in Example 1 was repeated except that 350 gr of methyl styrene and 15 gr of glycidyl acrylate were used instead of glycidyl methacrylate used to form the hard phase. An interpolymer was obtained.

(6) A method for producing polyacetal.

To the kneader having two Σ blades, 2500g of the multiphase interpolymer obtained in (5), 15kg of trioxane, 750gr of ethylene oxide, 0.50gr of boron trifluoride and 50gr of methylal were added, and the mixture was polymerized at 80 ° C for 45 minutes. Next, 1200 gr of triethylamine and 5 kg of water were added to this kneader, and the polymer was stabilized by stirring at 150 ° C. for 30 minutes. A stabilizer was added to this polymer and pelletized with a 30 mmφ single screw extruder.

The MI of this polyacetal was 27.5 gr / 10 minutes, and the Izod impact value was 52 kg · cm / cm, indicating excellent impact resistance.

Examples 5 to 12 (7) A method for producing a multiphase interpolymer having an epoxy group in the outermost phase.

A soft phase and a hard phase having an epoxy group were formed from the vinyl polymerizable monomers shown in Table 1, respectively.

(8) A method for producing polyacetal.

Instead of the multiphase interpolymer used in Example 4,
Other than using the multiphase interpolymer obtained in (7),
All the reagents used in Example 4 were used and operated in the same manner as in Example 4 to synthesize polyacetal.

The MI and Izod impact value of this polyacetal are also shown in Table 1. In all of the examples, polyacetal having excellent impact resistance was obtained.

Comparative Example 1 The procedure of Example 1 was repeated except that the use of the glycidyl methacrylate used for forming the hard phase (outermost phase) in Example 1 was stopped, and the procedure of Example 1 was repeated. Got united.

The MI of this polymer is 2.4 gr / 10 minutes, and the Izod impact value is 18 kg.
・ It was cm / cm. If a multiphase interpolymer having no epoxy group in the outermost phase is used, a polyacetal excellent in impact resistance cannot be obtained.

Comparative Example 2 A polymer was obtained in the same manner as in Example 2, except that the use of glycidyl ethyl methacrylate used in forming the hard phase in Example 2 was stopped and the reagents used in Example 2 were used. .

The MI of this polymer is 9.1 gr / 10 minutes, and the Izod impact value is 16 kg.
・ It was cm / cm. The impact resistance of the polymer of this comparative example is inferior to that of Example 2.

Comparative Example 3 A polymer was obtained in the same manner as in Example 3, except that the use of glycidyl acrylate used in Example 3 was stopped and the reagents used in Example 3 were used.

The MI of this polymer is 27.0 gr / 10 minutes, and the Izod impact value is 14k.
It was g · cm / cm, and the Izod impact value was inferior to that of Example 3.

(Effect of the invention) In the present invention, since the multi-phase interpolymer that constitutes the outermost phase contains an epoxy group, the obtained polyacetal does not impair the properties of the polyacetal itself, and has extremely high impact resistance. Will have.

Claims (2)

[Claims] 1. Formaldehyde or trioxane is homopolymerized in the presence of a multiphase interpolymer having a multiphase structure of two or more phases composed of a repeating soft phase and a hard phase, and having an epoxy group in the outermost phase thereof. A method for producing a polyacetal having excellent impact resistance, which is characterized in that 2. Formaldehyde or trioxane and a cyclic ether in the presence of a multiphase interpolymer having a multiphase structure of two or more phases composed of a repeating soft phase and a hard phase and having an epoxy group in the outermost phase thereof. Alternatively, a method for producing a polyacetal having excellent impact resistance, which comprises copolymerizing with a cyclic formal.