JP2517647B2 - Polyoxymethylene resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a polyoxymethylene resin composition having excellent heat resistance stability. More specifically, it relates to a polyoxymethylene resin composition which is excellent in melt standing stability at high temperature, melt viscosity stability, and heat aging resistance.

<Prior Art> Polyoxymethylene is known as an engineering plastic having high crystallinity and excellent mechanical properties. However, because of its chemical structure, it is very susceptible to oxidative deterioration, so various heat stabilizers have been blended for practical use.

For example, JP-B-46-35980 discloses a technique for improving heat resistance stability by adding and mixing a phenolic antioxidant, an alkaline earth metal salt and a tertiary aliphatic amine to a polyoxymethylene resin. There is.

Further, Japanese Patent Publication No. 55-18740 discloses a technique of blending a phenoxy resin with polyoxymethylene for the purpose of improving adhesiveness and heat discoloration resistance.

<Problems to be Solved by the Invention> However, in the method disclosed in Japanese Patent Publication No. 46-35980, since an aliphatic amine having a relatively low molecular weight is used, it is volatilized in a molten state. Or, the amine itself was decomposed, and the improvement in heat resistance stability of polyoxymethylene was lower than expected.

Further, as disclosed in JP-B-55-18740, the improvement of heat resistance stability of polyoxymethylene was very low only by blending phenoxy resin with polyoxymethylene.

<Means for Solving the Problems> The present inventors have found the present invention as a result of intensive studies to solve the above problems.

That is, the present invention provides (1) 0.001 to 100 parts by weight of polyoxymethylene, and (a) a hindered phenol having a molecular weight of 300 or more.
5 parts by weight (b) 0.001 to 5 parts by weight of at least one metal hydroxide selected from magnesium hydroxide, calcium hydroxide, strontium hydroxide and barium hydroxide (c) 0.001 to 5 parts by weight of phenoxy resin Is a resin composition.

The hindered phenol used in the present invention is a compound having a phenol structure having an alkyl group having 1 to 5 carbon atoms on both sides of a hydroxyl group and having a molecular weight of 300.
That is all. Specifically, 2,2'-methylene-bis (4-methyl-6-t-butylphenol), triethylene glycol-bis [3- (3-t-butyl-5-
Methyl-4-hydroxyphenyl) propionate],
Pentaerythrityl-tetrakis [3- (3,5-di-t
-Butyl-4-hydroxyphenyl) propionate], 2,2-thio-diethylenebis [3- (3,5-di-t
-Butyl-4-hydroxyphenyl) propionate], N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide), 1,3,5-
Trimethyl-2,4,6-tris (3,5-di-t-butyl-4
-Hydroxybenzyl) benzene, 1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-
Octylthio) -6- (4-hydroxy-3,5-di-t
-Butylanilino) -1,3,5-triazine, octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 2,2-thiobis (4-methyl-)
6-t-butylphenol), 3,5-di-t-butyl-
4-Hydroxybenzylphosphonate-diethyl ester, 1,3,5-tris (4-t-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid, 1,1,3
-Tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,1-bis (2-methyl-4-hydroxy-5-t-butylphenyl) butane, N, N'-
Examples thereof include bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine. Among them, 2,2'-methylene-bis (4-methyl-6-
t-butylphenol), triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] 1,6-hexanediol-bis [3- (3,5-di-t -Butyl-4-hydroxyphenyl) propionate], pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], N, N'-hexamethylenebis (3,5 -Di-t-butyl-4-hydroxy-hydrocinnamamide), 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene preferable.

When the molecular weight is less than 300, the bleeding phenomenon is remarkable, the appearance of the resin composition is impaired, and the heat stability is deteriorated, which is not preferable. The addition amount is 0.001 to 5 parts by weight, preferably 0.1 to 3.0 parts by weight, based on 100 parts by weight of the polyacetal resin. If it is less than 0.001 part by weight, the heat resistance stability of the polyacetal resin is not sufficient, and if it is more than 5 parts by weight, the bleeding phenomenon is observed or mechanical properties are deteriorated, which is not preferable.

The magnesium hydroxide, calcium hydroxide, strontium hydroxide and barium hydroxide used in the present invention may be anhydrous salts or may contain water of crystallization. The addition amount is 0.001 to 5 parts by weight, preferably 0.1 to 3 parts by weight, based on 100 parts by weight of polyoxymethylene. If it is less than 0.001 part by weight, the effect of addition is not obtained, and if it exceeds 5 parts by weight, mechanical properties are deteriorated and the like, which is not preferable.

The phenoxy resin used in the present invention is a number average molecular weight of 1,00 obtained from dihydric phenol and epichlorohydrin.
It is a thermoplastic resin of 0 to 100,000 and its structural unit is represented by (B).

However, X ₁ and X ₂ represent a hydrogen atom or a halogen atom, and R represents methylene, ethylene, ethylidene, butylidene, propylidene, isopropylidene, S, SO ₂ , O, Represents a direct bond.

At first glance, it is similar to an epoxy resin, but it is a resin that does not contain an epoxy group at the end and is stable to heat. The addition amount is 0.001 to 5 parts by weight, preferably 0.1 to 3 parts by weight, based on 100 parts by weight of polyoxymethylene. If it is less than 0.001 part by weight, the effect of addition is not obtained, and if it exceeds 5 parts by weight, mechanical properties are deteriorated, which is not preferable.

The polyoxymethylene used in the present invention is an oxymethylene homopolymer and an oxymethylene unit mainly containing oxymethylene units and containing 15 wt% or less of oxyalkylene units having 2 to 8 adjacent carbon atoms in the main chain. Means a methylene copolymer.

The oxymethylene homopolymer is produced, for example, by introducing substantially anhydrous formaldehyde into an organic solvent containing a basic polymerization catalyst such as an organic amine to polymerize it, and then acetylating the terminal with acetic anhydride.

The oxymethylene copolymer is, for example, a substantially anhydrous trioxane and a copolymerization component such as ethylene oxide, 1,3-dioxolane or 1,3-dioxepane dissolved or suspended in an organic solvent such as cyclohexane. Then, a Lewis acid catalyst such as boron trifluoride / diethyl etherate is added and polymerized, and unstable terminals are decomposed and removed.

Alternatively, without using any solvent, trioxane, a copolymerization component and a catalyst are introduced into a self-cleaning stirrer to perform bulk polymerization, and then unstable terminals are decomposed and removed for production.

Particularly preferable is to polymerize formaldehyde and / or trioxane and other cyclic ether in the presence of a Lewis acid catalyst under substantially anhydrous and solvent-free conditions, and then to give a hindered amine compound represented by the general formula (A). It is a polymer obtained by adding and stopping the polymerization reaction.

(In the formula, R ¹ represents a hydrogen atom or a monovalent organic residue having 1 to 30 carbon atoms. R ^{2 to} R ⁵ each represent an alkyl group having 1 to ⁵ carbon atoms, which may be the same or different. May be n
Represents an integer of 1 or more, and R ⁶ represents an n-valent organic residue. ) Specifically, the following compounds are used.

Among these, especially bis (2,2,6,6-tetramethyl-4-piperidinyl) sebacate (G-1), bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate (G -2), 1,2,3,4-butanetetracarboxylic acid tetrakis (2,2,6,6-tetramethyl-4-piperidinyl) ester (T-1), poly {[6- (1,1, 3,3-Tetramethylenebutyl) amino-1,3,5-triazine-2,4
-Diyl] [(2,2,6,6-tetramethyl-4-piperidinyl) imino] hexamethylene [(2,2,6,6-tetramethyl-4-piperidinyl) imino]} (U-1) preferable.

The hindered amine compound may be added as it is, but may be added as a solution of an organic solvent in order to promote contact with the polymerization catalyst. As the organic solvent at that time, aromatic hydrocarbons such as benzene, toluene and xylene, aliphatic hydrocarbons such as n-hexane, n-heptane and cyclohexane, alcohols such as methanol and ethanol, chloroform, 1, Examples thereof include halogenated hydrocarbons such as 2-dichloroethane, ketones such as acetone and methyl ethyl ketone.

It is preferable to add the hindered amine compound so that a hindered amine structure having an equimolar amount or more to the polymerization catalyst used exists. Even if the number of moles of the hindered amine structure is less than the number of moles of the polymerization catalyst used, the catalyst deactivating effect can be seen, but the heat stability of the obtained polymer is slightly lowered, so that the target heat stability cannot be achieved. It is necessary to adjust the addition amount according to the situation.

The polyoxymethylene resin composition of the present invention includes known colorants (pigments, dyes), conductive agents such as carbon black, flame retardants, reinforcing agents such as glass fibers, carbon fibers, aramid fibers, ceramic fibers, silica and clay. , Fillers such as glass powder, lubricants, nucleating agents, release agents, plasticizers, adhesives, adhesives,
Although an antistatic agent or the like can be optionally contained, in particular, when a nitrogen compound capable of reacting with formaldehyde and chemically trapping formaldehyde is added,
Further, the heat resistance is improved, which is preferable. Examples of such a nitrogen compound include an amide compound, a urethane compound, a pyridine derivative, a pyrrolidone derivative, a urea derivative, a triazine derivative, a hydrazine derivative and an amidine compound, and specifically, N, N-dimethylformamide, N, N. -Dimethylacetamide, N, N-diphenylformamide,
N, N-diphenylacetamide, N, N-diphenylbenzamide, N, N, N ′, N′-tetramethyladipamide, oxalic acid dianilide, adipic acid dianilide, N-phenylacetanilide, nylon 6, nylon 11, nylon, nylon 12
Homopolymers or copolymers of lactams such as adipic acid, sebacic acid, decanedicarboxylic acid, dicarboxylic acids such as dimer acid and ethylenediamine, tetramethylenediamine, hexamethylenediamine, diamines such as metaxylylenediamine Derived polyamide homopolymers or copolymers, polyamide copolymers derived from lactams and dicarboxylic acids and diamines,
Polyacrylamide, polymethacrylamide, N, N-bis (hydroxymethyl) sveramide, poly (γ-methylglutamate), poly (γ-ethylglutamate),
Amide compounds such as poly (N-vinyllactam) and poly (N-vinylpyrrolidone), diisocyanates such as toluene diisocyanate and diphenylmethane diisocyanate, and glycols such as 1,4-butanediol and poly (tetramethylene oxide) glycols, poly,
Polyurethane derived from polymer glycols such as butylene adipate and polycaprolactone, melamine, benzoguanamine, acetoguanamine, N-butylmelamine, N-phenylmelamine, N, N'-diphenylmelamine, N, N ', N "-tri Phenylmelamine, N-methylolmelamine, N, N'-dimethylolmelamine, N, N ', N "
-Trimethylol melamine, 2,4-diamino-6-benzyloxytriazine, 2,4-diamino-6-butoxytriazine, 2,4-diamine-6-cyclohexyltriazine, melem, triazine derivatives such as melam, N-
Phenylurea N, N'-diphenylurea, thiourea, N-
Urea derivatives such as phenylthiourea, N, N'-diphenylthiourea, ethyleneurea, nonamethylene polyurea, phenylhydrazine, diphenylhydrazine, benzaldehyde hydrazone, benzaldehyde semicarbazone, benzaldehyde 1-methyl-1-phenylhydrazone, benzaldehyde Thiosemicarbazone, 4-
Upon induction of hydrazine such as hydrazone of (dialkylamino) benzaldehyde, dicyandiamide, guanzine, guanidine, aminoguanidine, guanine, guanacrine, guanoclor, guanoxane, guanosine,
Amidine, amidine compounds such as N-amidino-3-amino-6-chloropyrazinecarboxamide, poly (2-vinylpyridine), poly (2-methyl-5-vinylpyridine), poly (2-ethyl-5-vinyl) Pyridine), 2-vinylpyridine / 2-methyl-5-vinylpyridine copolymer, 2-vinylpyridine / styrene copolymer, and other pyridine derivatives.

The amount of the above nitrogen compound added is 10% by weight of polyoxymethylene.
0.001-5 parts by weight, preferably 0.1-3, relative to 0 parts by weight
Parts by weight.

If it is less than 0.001 part by weight, the effect of addition is not seen, and if it is more than 5 parts by weight, a bleeding phenomenon or the like appears, which is not preferable.

<Examples> Hereinafter, the present invention will be described with reference to Examples.

The mechanical properties, MI value, melt standing stability, melt torque stability, polymer melting point, and crystallization temperature of the molded products shown in Examples and Comparative Examples were measured as follows.

Mechanical Properties of Molded Products Using an injection molding machine with an injection capacity of 5 ounces, a tensile test of 1/8 inch thickness x 1/2 inch width with a cylinder temperature of 200 ° C, a mold temperature of 80 ° C and a molding cycle of 60 seconds. Piece and 1 / 2i
An Izod impact test piece with nch thickness and 1/2 inch width was injection molded. These test pieces were used to measure tensile properties according to ASTM D-638 and notched Izod impact values according to ASTM D-256.

Using pellets dried in a hot air circulation oven with MI value of 80 ° C for 3 hours, according to ASTM D-1238, temperature 190 ° C, load 2,160
Measured in g.

Melting and Stability Stability About 5 g of pellets were precisely weighed in an aluminum cup, and allowed to stand in a hot air circulation oven at 240 ° C. for 2 hours, and then evaluated by weight retention (%).

Melt torque stability Using a 100 cc mixer of Labo Plastomill manufactured by Toyo Seiki Co., Ltd., 90 g of pellets were melt-kneaded at 50 rpm and evaluated by the torque reduction rate (kg · cm / min).

Polymer melting point, crystallization temperature Use a differential scanning calorimeter to raise the temperature at a rate of 10 ° C / min in a nitrogen atmosphere, measure the polymer melting point (Tm), then
The temperature was lowered in minutes and the crystallization temperature (Tc) was measured.

Reference Example 1 Production of Polyoxymethylene Production of Polyoxymethylene POM-1 A polymerization reaction tank having a diameter of 30 cm and a depth of 3 m and a stirring blade and a formaldehyde gas supply nozzle at the bottom was filled with n-hexane. Di-n-butyltin dimaleate was added to this.
0.5 wt% was dissolved, and formaldehyde gas was introduced from a supply nozzle. As the formaldehyde gas, paraformaldehyde was thermally decomposed at 140 to 180 ° C. and then purified, which was introduced at a rate of 2 kg / h. The inside of the polymerization tank was adjusted to 60 ° C. by flowing cold water or warm water through the jacket. Although fine polymer particles are gradually generated in the polymerization tank, the polymer slurry is extracted and the catalyst solution (n-hexane) is supplied so that the polymer solid content is maintained at about 50% by weight.
Separate the polymer that was taken out, wash it thoroughly with water, and then
It was put into 10 times the volume of acetic anhydride. Further, 0.1% by weight of acetic anhydride was added to sodium acetate, and the mixture was heated with stirring at 139 ° C for 5 hours. After the reaction mixture was cooled to room temperature, the polymer was separated, thoroughly washed with acetone and water, and then dried.

This polymer has a melting point of 179 ° C, crystallization temperature of 150 ° C, MI = 8.
Was eight.

Manufacture of polyoxymethylene POM-2 2 with 26 convex lens type paddles per axis 2
The following raw materials were supplied to an axial kneader (25 mmφ, L / D = 10.2) to carry out polymerization.

Polymerization temperature is by passing warm water through the outer jacket,
The temperature was controlled to about 90 ° C and the rotation speed was set to 100 rpm.
Ethylal as a molecular weight modifier was dissolved in trioxane, and boron trifluoride / diethyl etherate as a polymerization catalyst was dissolved in benzene and supplied to the kneader.
Further, a premixing zone was provided so that the 1,3-dioxolane and the catalyst solution were premixed immediately before being supplied to the kneader.

 The polymer was obtained as a white fine powder at 445 g / h.

The polymer thus obtained was put into a 3% aqueous ammonia solution and stirred. The polymer was separated, washed with water and then with acetone, then put into a 10% aqueous ammonia solution, and heated and stirred in an autoclave at 150 ° C. for 3 hours. After cooling to room temperature, the polymer was separated, washed with water, then acetone, and dried. The melting point of this polymer was 167 ° C., the crystallization temperature was 147 ° C., and MI = 9.0.

Production of polyoxymethylene POM-3 2.7g of bis (1,2,2,6,6-pentamethyl-4-piperidinyl) was polymerized in the same manner as POM-2 and 1kg of white fine powder discharged from the kneader was discharged. ) Add a solution of sebacate in 20 ml of benzene and mix in a Henschel mixer.
The catalyst was deactivated by stirring for 1 minute to obtain POM-3. The melting point of this polymer was 167 ° C., the crystallization temperature was 147 ° C., and MI = 6.4.

Examples 1 to 23 To the polyoxymethylene POM-1 to 3 produced in Reference Example, the additives were added at the compounding ratio shown in Table 1, and 45 mmφ,
It was melt-kneaded by a twin-screw extruder with a vent of L / D = 31.5.
The kneading temperature was set to 220 ° C to 240 ° C. Table 3 shows the results of measuring the physical properties of the obtained composition.

Comparative Examples 1 to 18 The additives were added to the polyoxymethylene POM-1 to 3 produced in Reference Example at the compounding ratio shown in Table 2, and 45 mmφ, L /
Melt kneading was performed by a twin-screw extruder with a vent having D = 31.5. The kneading temperature was set to 220 to 240 ° C. Table 4 shows the results of measuring the physical properties of the obtained composition.

From Examples 1 to 4, 7 to 12 and 15 to 20, resin compositions containing hindered phenol, alkaline earth metal hydroxide and phenoxy resin are mechanical properties, melt stability and melt torque. It can be seen that the stability is excellent. Further, it can be seen that various physical properties are excellent regardless of the kind of hindered phenol, the kind of alkaline earth metal hydroxide, and the kind of phenoxy resin.

Further, from Examples 5 to 6, 13 to 14 and 21 to 23, it is understood that the addition and kneading of the formaldehyde scavenger further improves the stability in melting and standing and the stability in melting torque.

Comparing Examples 7 to 14 and 15 to 23, it can be seen that even in the same copolymer, the catalyst deactivated by adding the hindered amine compound is more excellent in melt standing stability and melt torque stability.

From Comparative Examples 1, 7, and 13, it can be seen that the melt standing stability and the melt torque stability decrease unless the phenoxy resin is added. From Comparative Examples 2, 8 and 14, it can be seen that the melting standing stability and the melting torque stability are lowered even when the alkaline earth metal oxide is not added.

From Comparative Examples 3, 9 and 15, it can be seen that when hindered phenol is not added, the degree of polymerization is remarkably lowered, and the mechanical properties, the stability in melting and standing, and the stability of melting torque are remarkably lowered, and it cannot be used as a product.

From Comparative Examples 4, 10, and 16, it can be seen that the mechanical properties are deteriorated when a large amount of hindered phenol is added.

From Comparative Examples 5, 11, and 17, it is understood that when a large amount of alkaline earth metal hydroxide is added, mechanical properties, stability in melting and standing, and stability in melting torque are deteriorated.

From Comparative Examples 6, 12, and 18, it is understood that mechanical properties are deteriorated when a large amount of phenoxy resin is added.

<Effects of the Invention> The resin composition of the present invention is excellent in heat resistance stability and mechanical properties, and thus can be used in a wide variety of applications such as machine mechanism parts and electric / electronic parts.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C08L 71:00) C08L 71:00) (56) References JP-A-49-88936 (JP, A) ) JP 62-70447 (JP, A) JP 61-69859 (JP, A) JP 60-90250 (JP, A) JP 60-11550 (JP, A) JP 51- 41750 (JP, A)

Claims (5)

(57) [Claims] (1) 0.001 to (1) a hindered phenol having a molecular weight of 300 or more per 100 parts by weight of polyoxymethylene.
5 parts by weight (b) 0.001 to 5 parts by weight of at least one metal hydroxide selected from magnesium hydroxide, calcium hydroxide, strontium hydroxide and barium hydroxide (c) 0.001 to 5 parts by weight of phenoxy resin A resin composition comprising: 2. The hindered phenol is 2,2'-methylene-bis (4-methyl-6-t-butylphenol),
Triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5-di-
t-butyl-4-hydroxyphenyl) propionate], pentaerythrityl-tetrakis [3- (3,5-
Di-t-butyl-4-hydroxyphenyl) propionate], N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) and 1,
1,5 selected from 3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene
The composition of claim 1 which is one or more compounds. 3. The composition according to claim 1, wherein the polyoxymethylene is a polymer obtained by copolymerizing formaldehyde and / or trioxane with another cyclic ether in the presence of a polymerization catalyst. 4. Polyoxymethylene copolymerizes formaldehyde and / or trioxane with another cyclic ether in the presence of a polymerization catalyst, and then adds a hindered amine compound represented by the general formula (A) to terminate the polymerization reaction. The composition according to claim 1, which is a polymer obtained by the method. (In the formula, R ¹ represents a hydrogen atom or a monovalent organic residue having 1 to 30 carbon atoms. R ^{2 to} R ⁵ each represent an alkyl group having 1 to ⁵ carbon atoms, which may be the same or different. It may be attached.
n represents an integer of 1 or more, and R ⁶ represents an n-valent organic residue. ) 5. The hindered amine compound is bis (2,2,6,6).
-Tetramethyl-4-piperidinyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, 1,2,3,4-butanetetracarboxylic acid tetrakis (2,2,6, 6-tetramethyl-4-piperidinyl) ester and poly {[6- (1,1,3,3-tetramethylenebutyl) amino-1,3,5-triazine-2,4-diyl] [(2,
2. One or more compounds selected from 2,6,6-tetramethyl-4-piperidinyl) imino] hexamethylene [(2,2,6,6-tetramethyl-4-piperidinyl) imino]}. 4. The composition according to 4.