KR20160055988A - Polyoxymethylene resin composition having good thermal-stability - Google Patents

Abstract

The present invention relates to a polyoxymethylene resin composition comprising a polyoxymethylene polymer, a lactone-based antioxidant, multi-branched polyethylene glycol, and an alkaline earth metal phosphate-based compound and, more specifically, to a polyoxymethylene resin composition has excellent thermal stability and can reduce formaldehyde emitted during a producing process by producing the polyoxymethylene polymer using a novel antioxidant and a heat stabilizer.

Description

[0001] The present invention relates to a polyoxymethylene resin composition having good thermal stability,

The present invention relates to a polyoxymethylene resin composition, and more specifically, to a polyoxymethylene resin composition which is excellent in thermal stability and can reduce the amount of formaldehyde released during the manufacturing process.

Generally, polyoxymethylene resins are prepared by bulk polymerization, solution polymerization or suspension of trioxane mono or trioxane with cyclic ethers and / or cyclic acetals to produce oxymethylene homopolymers or copolymers. Such a method is disclosed in various prior art documents including Japanese Patent Application No. 36-14640 and is known in the art.

Since polyoxymethylene single or copolymers have excellent mechanical properties, creep resistance, fatigue resistance and abrasion resistance, they are widely used in various fields such as electric, electronic parts and mechanical mechanisms. However, such a polyoxymethylene resin has a disadvantage that thermal stability is insufficient and decomposition is liable to be caused by thermal, mechanical, or additives during the molding process. Particularly, when an unstable terminal is present in the resin, it causes an increase in odor during molding and poor workability. Examples of such decomposing groups include the case where depolymerization is supplied from the end of the resin through depolarization, the case where the main chain is cleaved by mechanical shear external force during molding, and the residual impurities in the polyoxymethylene resin or the pigment And the decomposition reaction by oxidation is another example.

Various methods have been proposed to improve the thermal stability of the polyoxymethylene resin. Examples of methods for improving the thermal stability include amines, amides, and hydrazines which can react with decomposition gases such as formaldehyde generated by thermal decomposition A method of adding an additive such as water or the like is proposed. For example, Japanese Patent Application Laid-Open No. 10-1592 discloses a method of adding an acrylamide and a boronic acid compound to a polyoxymethylene resin, and JP-A-59-213752 discloses a method of adding an alanine compound to a polyoxymethylene resin Method is described. However, in the case of the above methods, the additive is thermally unstable to induce yellowing, thereby causing a mold deposit due to the bleed-out of the additive, thereby limiting the improvement of thermal stability.

Another method for improving thermal stability is to stabilize unstable polyoxymethylene molecular ends by polymerizing formaldehyde, trioxane, etc. in the case of a polyoxymethylene homopolymer in the presence of an anionic catalyst, A method of capping the unstable terminal is proposed. For example, Japanese Patent Publication No. 33-6099, U.S. Patent No. 2,964,500, and Japanese Patent Publication No. 36-3492 disclose a method in which an isocyanate group is reacted with a terminal hydroxy group to urethanize the terminal. However, in the above methods, the oxymethylene main chain can easily be destroyed by a mechanism such as solvolisys, and a thermally highly unstable resin is obtained due to the presence of the terminal unreacted capping polymer. In order to overcome the disadvantages of such a polyoxymethylene homopolymer, a specific comonomer, that is, a copolymer obtained by copolymerizing a cyclic ether such as ethylene oxide or a cyclic formal such as dioxolane with formaldehyde, trioxane or the like in the presence of a catalyst Are randomly dispersed and introduced into the homopolymer. However, the copolymers produced by this method must be accompanied by a stabilization process because their terminal groups are very unstable.

Numerous studies have suggested a technical solution to the above-mentioned problem. Mostly, the method of forcibly decomposing unstable terminal sites to arrive at the position of the comonomer is characterized in most of the inventions. For example, Japanese Patent Publication No. 60-63216 and Japanese Patent Publication No. 60-69121 disclose a method of decomposing and stabilizing a terminal with an alkaline aqueous solution having a pH of 7 or more under a nonuniform medium after polymerization, and U.S. Patent No. 1,407,145 also discloses a method in which basic alcohol A method of hydrolyzing a terminal in combination with an antacid and an antioxidant under a medium of a flow and a heterogeneous phase has been proposed, but this is also not satisfactory.

Japan Special Section 36-14640 Japanese Patent Laid-open No. 10-1592 Japanese Patent Office No. 59-213752 Japanese Special Operations No. 33-6099 U.S. Patent 2,964,500 Japanese Special Section 36-3492 Japanese Patent Office No. 60-63216 Japanese Patent Office No. 60-69121 U.S. Patent No. 1,407,145

In order to solve the above-mentioned problems, it is an object of the present invention to provide a polyoxymethylene resin composition having excellent thermal stability by removing radicals, acids and residual impurities which cause depolymerization during processing.

In order to accomplish the above object, the present invention relates to a polyoxymethylene resin composition having excellent thermal stability by completely removing radicals, acids and residual impurities which cause depolymerization during processing,

More specifically, as one example, an alkyl-substituted melamine polymerization terminator is added, and a polyoxymethylene polymer having excellent heat stability, which is prepared by adding a lactone-based antioxidant, a multi-component polyethylene glycol and an alkaline earth metal phosphate compound to a reaction- Methylene resin composition.

The present invention relates to a polyoxymethylene resin composition comprising a polyoxymethylene polymer or copolymer, a lactone antioxidant, a multi-component polyethylene glycol, and an alkaline earth metal phosphate compound.

Still another aspect of the present invention relates to a polyoxymethylene resin composition comprising the structured lactone antioxidant of the following formula (2).

(2)

(In the general formula 2 R ₁ and R ₂ is an alkyl group having 1 to 10, Ar is a carbon number of 6 to 30 aromatic or non-aromatic ring compound, wherein the aromatic or non-aromatic ring compound is one or more unsubstituted or -CH ₃ , -C ₂ H ₅ , -C ₃ H ₇ or -C ₄ H _9. )

Still another aspect of the present invention relates to a polyoxymethylene resin composition having a lactone antioxidant in an amount of 0.0005 to 1 part by weight based on 100 parts by weight of the polyoxymethylene polymer.

Another aspect of the present invention relates to a polyoxymethylene resin composition comprising a multi-component polyethylene glycol having a structure represented by the following formula (3) and having from 0.01 to 5 parts by weight based on 100 parts by weight of the polyoxymethylene polymer.

(3)

(Wherein a is an integer of 2 to 200).

Still another aspect of the present invention relates to a polyoxymethylene resin composition having an alkaline earth metal phosphate compound in an amount of 0.001 to 5 parts by weight based on 100 parts by weight of the polyoxymethylene polymer.

Still another aspect of the present invention relates to a polyoxymethylene resin composition wherein the polyoxymethylene resin composition further comprises an antioxidant other than the lactone antioxidant.

Still another aspect of the present invention relates to a polyoxymethylene resin composition characterized by adding a polymerization terminator after the polymer or copolymer has a weight average molecular weight of 10,000 to 400,000 g / mol.

A feature of the present invention is to provide a polyoxymethylene polymer or copolymer which has a low weight loss rate, low amount of molded product formaldehyde generation and a low melt index, a very good thermal stability by using a lactone based antioxidant, a multi-branched polyethylene glycol and an alkaline earth metal phosphate- And the like.

In this case, it is important to use a lactone antioxidant, a multi-component polyethylene glycol, and an alkaline earth metal phosphate compound together as an additive. When only two of them are added except for one of them, the polyoxymethylene resin composition is thermally stable More formaldehyde gas, and more than three times more formaldehyde gas.

Hereinafter, each component according to the present invention will be described.

First, the polyoxymethylene resin composition will be described.

The polyoxymethylene resin to be polymerized by using the BF ₃ coordination compound polymerization catalyst is a homopolymer composed of oxymethylene units represented by the following formula (4), or a unit of the following formula (4) and a unit of the following formula ≪ / RTI >

[Chemical Formula 4]

[Chemical Formula 5]

X ₁ and X ₂ may be the same or different from each other and are each hydrogen or an alkyl group having 1 to 4 carbon atoms, X ₁ and X ₂ are not both hydrogen, and x is 2 to 4, Lt; / RTI >

The polyoxymethylene resin is not particularly limited, but preferably has a weight average molecular weight in the range of 10,000 to 400,000 g / mol.

The oxymethylene homopolymer may be prepared by polymerizing formaldehyde or a cyclic oligomer thereof, that is, trioxane. The oxymethylene copolymer to which the unit of the formula (4) and the unit of the formula (5) are bonded may be a formaldehyde or a Can be obtained by randomly copolymerizing a cyclic oligomer with a cyclic ether represented by the following formula (6) or a cyclic formal represented by the following formula (7).

[Chemical Formula 6]

(7)

X ₃ , X ₄ , X _5, and X ₆ may be the same or different from each other and are each hydrogen or an alkyl group having 1 to 4 carbon atoms, and may be bonded to the same carbon atom or different carbon atoms And n and m are integers of 2 to 6, respectively.

Of the comonomers used in the random copolymerization, examples of the cyclic ether include ethylene oxide, propylene oxide, butylene oxide, and phenylene oxide. Examples of the cyclic formaldehyde include 1,3-dioxolane, diethylene glycol formal, 1,3 -Propanediol formal, 1,4-butanediol formal, 1,3-dioxepanformal, 1,3,6-trioxocane and the like. Preferably, one or more monomers selected from monomers such as ethylene oxide, 1,3-dioxolane and 1,4-butanediol formal can be used. These monomers can be used in combination with trioxane or formaldehyde And the random copolymerization is carried out using Lewis acid as a catalyst to obtain an oxymethylene copolymer. The copolymer thus obtained has a melting point of 150 ° C or more and has two or more bonding carbon atoms in the main chain.

In the above oxymethylene copolymer, the ratio of the oxymethylene linkage structure to the oxymethylene repeat unit is in the range of 0.05 to 50 mole times, preferably 0.1 to 20 mole times.

Examples of the polymerization catalyst used in the polymerization reaction of the polyoxymethylene resin include BF ₃ OH ₂ , BF ₃ O (CH ₂ CH ₃ ) ₂ , BF ₃ O (CH ₂ CH ₂ CH ₂ CH ₃ ) ₂ , BF ₃ CH ₃ CO ₂ H, BF ₃ PF ₅ HF, and BF ₃ -10-hydroxyacetophenol, and preferably BF ₃ O (CH ₂ CH ₃ ) ₂ and BF ₃ O (CH ₂ CH ₂ CH ₂ CH ₃ ) ₂ is preferably used. The amount of the polymerization catalyst to be added is not particularly limited, but is preferably in the range of 2 × 10 ^-6 to 2 × 10 ^-2 mol per mol of trioxane.

The polymerization can be carried out in the form of bulk polymerization, suspension polymerization or solution polymerization, and the temperature during the polymerization reaction is not limited, but can be carried out, for example, in the range of 0 to 100 占 폚, preferably 20 to 80 占 폚 have.

In the polymerization of polyoxymethylene, an alkyl-substituted phenol or an ether may be used as a chain transferring agent, and alkyl ethers such as dimethoxymethane are particularly preferably used.

Next, the lactone-based antioxidant will be described.

The lactone-based antioxidant used in the present invention is a compound added to improve the thermal oxidation stability of the resin composition according to the present invention, and is a compound having a structure represented by the following formula (2).

(2)

Wherein [Formula 2] R ₁ and R ₂ is an alkyl group having 1 to 10, Ar is an aromatic or non-aromatic cyclic compound having 6 to 30 carbon atoms, said aromatic or non-aromatic ring compound is unsubstituted or substituted by one or more -CH ₃ , -C ₂ H ₅ , -C ₃ H ₇ or -C ₄ H ₉ .

The amount of the lactone antioxidant to be added is 0.0005 to 1 part by weight, preferably 0.001 to 0.5 part by weight based on 100 parts by weight of the polyoxymethylene polymer. In this range, the thermal stability is excellent and no discoloration occurs.

Next, the multi-component polyethylene glycol will be described.

The multi-branched polyethylene glycol used in the present invention has a structure represented by the following formula (3) and increases the thermal stability of the polyoxymethylene resin composition.

(3)

In Formula 3, a is an integer of 2 to 200.

The amount of the multi-component polyethylene glycol to be added is 0.01 to 5 parts by weight, preferably 0.05 to 1 part by weight, based on 100 parts by weight of the polyoxymethylene polymer. Within this range, the thermal stability is excellent and there is no yellowing.

Next, the alkaline earth metal phosphate compound will be described.

In addition, a metal such as an alkaline earth metal phosphate-based hwahapmulreul added, the alkaline earth metal is Be, Mg, Ca, Sr, and Ba in order to further improve the thermal stability of the resin composition according to the invention, but are not particularly limited and Ca ₃ (PO ₄ ) ₂ or the like is preferably added.

The amount of the alkaline earth metal phoshate compound added is 0.001 to 5 parts by weight, preferably 0.01 to 1 part by weight, based on 100 parts by weight of the polyoxymethylene polymer. In this range, the thermal stability is excellent and no discoloration occurs.

Next, the polymerization terminator will be described.

When the weight average molecular weight of the polyoxymethylene is 10,000 to 400,000 g / mol by the above polymerization reaction, a polymerization terminator is added to terminate the polymerization reaction. The polymerization terminator is not particularly limited as long as it can effectively stop the polymerization reaction. For example, an alkylated melamine having the following formula (1) can be used.

[Chemical Formula 1]

In the formula 1, R ₁ to R ₆ may be the same or different from each other and each represents -H, -CH ₂ OR ₇ , -CH ₂ OH, -CH ₃ , -C ₂ H ₅ or -C ₄ H ₉ Which one is chosen. Wherein R ₇ is -CH ₃ , -C ₂ H ₅ , -C ₄ H ₉ or -R ₈ CO ₂ R ₉ and R ₈ is -CH ₂ -, - (CH ₂ ) ₂ - or - (CH ₂ ) ₄ -, and R ₉ is -CH ₃ , -C ₂ H ₅ or -C ₄ H ₉ . Provided that R ₁ to R ₆ are not all hydrogen.

The addition amount of the polymerization terminator is preferably 0.01 to 50 moles of the BF ₃ coordination compound polymerization catalyst.

The polymerization terminator may be added in the form as it is or dissolved in an organic solvent. Examples of the organic solvent include aromatic hydrocarbons such as benzene, toluene and xylene, aliphatic hydrocarbons such as n-hexane, n-heptane and cyclohexane, alcohols such as methanol and the like, chloroform, dichloromethane, Halogenated hydrocarbons such as dichloroethane and the like, and ketones such as acetone, methyl ethyl ketone and the like.

Furthermore, it is preferable to add a sterically hindered phenol in order to further improve the oxidation stability of the resin composition according to the present invention. Examples of sterically hindered phenols include 2,2'-methylene-bis (4-methyl-6-t-butylphenol), 4,4'- methylene- bis (2,6- 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, 2,5-di- Di-t-butyl-4-hydroxybenzylphosphonate, diethyl-3,5-di-t-butyl-4-hydroxybenzylphosphonate, 2,6- Methyl-3,5-di-t-butyl-4-hydroxyhydrocinnamate, 3,5-di-t-butoxycarbonyl [2,2,2] Di-t-butyl-4-hydroxyphenyl-3,5-distearyl-thiotriazolylamine, 2 (2'-hydroxy-3 ', 5'- Di-t-butyl-4-hydroxymethylphenol, 2,4-bis- (n-octylthio) -6- (4-hydroxy- (3,5-di-t-butyl-4-hydroxy-hydrosine amide), octadecyl-3- (3 , 5-di-butyl-4-deoxyphenyl) propionate, 1,6- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], pentaerythritol-tetrakis [3- (3,5- (3-t-butylphenyl) propionate], triethylene glycol-bis [3- (3,5- Butyl-4-hydroxyphenyl) propionate, triethylene glycol-bis [3- (3,5-di- Thiodiethyl-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate].

Among these, triethylene glycol-bis-3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionate and the like are preferably added though not limited thereto.

The addition amount of the hindered phenol is 0.0001 to 5 parts by weight, preferably 0.01 to 1 part by weight based on 100 parts by weight of the polyoxymethylene polymer. Within the above range, the thermal stability is excellent, and the physical properties of the obtained molded article are not deteriorated.

The polyoxymethylene resin composition according to the present invention can reduce formaldehyde released during the manufacturing process by effectively removing radicals generated during processing and acid remaining in the polymer by using a stabilizing additive, and thus, has excellent thermal stability.

Hereinafter, the polyoxymethylene resin composition according to the present invention will be described in more detail, but the technical aspects of the present invention are not limited thereto.

The physical properties of the polyoxymethylene resin composition prepared through Examples and Comparative Examples were measured as follows.

(1) Weight reduction rate of the resin composition (thermal stability)

After the resin composition was treated at a vacuum pressure of 10 mmHg and a temperature of 222 占 폚 for 30 minutes, the thermal stability was evaluated by measuring the weight loss rate. The smaller the weight loss rate value, the better the thermal stability.

(2) Formaldehyde generation amount

The obtained polyoxymethylene resin composition was molded into a size of 100 mm x 40 mm x 2 mm, and then sealed in a 1 L capacity bottle containing 50 ml of water so as not to touch the water. The bottle thus prepared was allowed to stand at 60 DEG C for 3 hours, and the amount of formaldehyde collected in the water was measured by UV spectrophotometer to determine the amount of formaldehyde generated in the molded article. The smaller the value, the better the thermal stability.

(3) Melt index

The weight of the resin sample extruded at a temperature of 190 ° C. and a load of 2.16 kg for 10 minutes was measured in an orifice having a constant inner diameter. This value was a measure for evaluating the depolymerization rate of the resin. The larger the melt index value, Is high.

Hereinafter, the polyoxymethylene resin composition according to the present invention will be described in more detail with reference to Examples and Comparative Examples.

[Example 1]

After maintaining a 1 L capacity of the polymerization reactor at 50 ° C, 500 g of trioxane and 20 g of 1,3-dioxolane were injected into the reactor using a metering device. Then, BF ₃ O (CH ₂ CH ₃ ) ₂ 0.035 g (70 ppm) was added. Ten minutes after the addition of the polymerization catalyst, hexakis (methoxymethyl) melamine was added as a polymerization terminator in an amount of 2 moles (200 ppm, diluted with benzene) of the polymerization catalyst, and 10 minutes later, A polymer was obtained. Thereafter, the mixture was maintained at 230 DEG C using a Kneader (Labo Plastomill, manufactured by TOYOSEIKI) having two pairs of Σ-type blades, and then 100 parts by weight of triethylene glycol-bis-3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate, 0.01 part by weight of the lactone-based antioxidant shown in the following Table 1, polyoxyethylene pentaerythritol ether And 0.05 parts by weight of Ca ₃ (PO ₄ ) _{2 were} added, and the mixture was allowed to stand for 40 minutes under a nitrogen atmosphere to obtain a secondary polymer having a weight-average molecular weight of 200,000 g / mol. The properties of the resultant polyoxymethylene resin composition were evaluated by the above-mentioned measuring method, and the results are shown in Table 2 below.

[Examples 2 to 3]

A polyoxymethylene secondary polymer was obtained in the same manner as in [Example 1] except that the content of the polymerization composition and the content of the stabilizer composition were changed as shown in Table 1 below. The properties of the resultant polyoxymethylene resin composition were evaluated by the above-mentioned measuring method, and the results are shown in Table 2 below.

[Comparative Examples 1 to 8]

A polyoxymethylene secondary polymer was obtained in the same manner as in [Example 1] except that the content of the polymerization composition and the content of the stabilizer composition were changed as shown in Table 1 below. The properties of the resultant polyoxymethylene resin composition were evaluated by the above-mentioned measuring method, and the results are shown in Table 2 below.

division Polymerization composition Stabilizer composition (phr) catalyst
(ppm) Comonomer
(phr) Polymerization terminator
(ppm) end I All la Example 1 70 4 200 0.01 0.3 0.05 0.3 Example 2 70 4 200 0.01 0.3 0.05 - Comparative Example 1 70 4 200 - - - 0.3 Comparative Example 2 70 4 200 - 0.3 0.05 0.3 Comparative Example 3 70 4 200 0.01 - 0.05 0.3 Comparative Example 4 70 4 200 0.01 0.3 - 0.3 Example 3 70 0 200 0.01 0.3 0.05 0.3 Comparative Example 5 70 0 200 - - - 0.3 Comparative Example 6 70 0 200 - 0.3 0.05 0.3 Comparative Example 7 70 0 200 0.01 - 0.05 0.3 Comparative Example 8 70 0 200 0.01 0.3 - 0.3

1. Catalyst: BF ₃ O (CH ₂ CH ₃ ) ₂

2. Comonomer: 1,3-dioxolane

3. Polymerization stopper: hexakis (methoxymethyl) melamine (CYMEL303 made by CYTEC)

4. Stabilizer composition

  (A) Lactone based antioxidant (Eutec chemical AO-136)

  (B) Polyoxyethylene pentaerythritol ether (KPX Green chemical CAS number 30599-15-6)

  (C) Alkali earth metal phosphate compound (Budenheim C13-09)

(D) Triethylene glycol-bis-3- (3- tert -butyl-4-hydroxy-5-methylphenyl) propionate (SONGNOX 2450,

division Weight reduction rate
(%) Formaldehyde Emission Rate
(ppm) Melt Index
(g / 10 min) Example 1 15 35 9.0 Example 2 20 55 9.0 Comparative Example 1 40 130 9.9 Comparative Example 2 35 100 9.5 Comparative Example 3 29 88 9.5 Comparative Example 4 31 97 9.5 Example 3 21 110 1.5 Comparative Example 5 decomposition Comparative Example 6 45 155 1.9 Comparative Example 7 35 150 1.6 Comparative Example 8 42 152 1.7

As shown in Table 2,

[Example 1] to [Example 2] were found to have a very low thermal stability compared with [Comparative Examples 1] to [Comparative Example 4] because the weight reduction rate, the amount of molded product aldehyde generated and the melt index were small. It is also understood that [Example 3] also has excellent thermal stability because the weight reduction rate and the amount of formaldehyde generated are smaller than those of [Comparative Examples 5] to [Comparative Example 8].

Accordingly, the present invention provides a polyoxymethylene resin composition which is thermally stable with a novel antioxidant and a heat stabilizer, and is less likely to generate formaldehyde gas during molding and molding.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention. Therefore, the above description does not limit the scope of the present invention defined by the limitations of the following claims.

Claims (7)

A polyoxymethylene resin composition comprising a polyoxymethylene polymer or copolymer, a lactone antioxidant, a multi-component polyethylene glycol, and an alkaline earth metal phosphate compound. The method according to claim 1,
Wherein the lactone-based antioxidant has a structure represented by the following formula (2).
(2)

(In the general formula 2 R ₁ and R ₂ is an alkyl group having 1 to 10, Ar is a carbon number of 6 to 30 aromatic or non-aromatic ring compound, wherein the aromatic or non-aromatic ring compound is one or more unsubstituted or -CH ₃ , -C ₂ H ₅ , -C ₃ H ₇ or -C ₄ H _9. ) 3. The method of claim 2,
Wherein the lactone-based antioxidant is 0.0005 to 1 part by weight based on 100 parts by weight of the polyoxymethylene polymer. The method according to claim 1,
Wherein the polyelectrolyte-based polyethylene glycol has a structure represented by the following formula (3): 0.01 to 5 parts by weight based on 100 parts by weight of the polyoxymethylene polymer.
(3)

(Wherein a is an integer of 2 to 200). The method according to claim 1,
Wherein the alkaline earth metal phosphate compound is 0.001 to 5 parts by weight based on 100 parts by weight of the polyoxymethylene polymer. The method according to claim 1,
Wherein the polyoxymethylene resin composition further comprises an antioxidant other than the lactone antioxidant. 6. The method according to any one of claims 1 to 6,
Wherein the polymerization initiator is added after the polymer or copolymer has a weight average molecular weight of 10,000 to 400,000 g / mol.