JPH01204949A - Stabilized oxymethylene copolymer composition - Google Patents

Abstract

PURPOSE:To improve long-term resistance to hot water and long-term heat aging characteristics and to reduce deposit on a mold during fabrication, by compounding an oxymethylene copolymer with an alkaline earth metal salt of a specified ester. CONSTITUTION:The title compsn. is obtd. by compounding 100pts.wt. oxy methylene copolymer (A) consisting of oxymethylene units of formulae I and II (wherein R<1-2> are each H, an alkyl or an aryl and m is 2-6), 0.01-5pts.wt. alkaline earth metal salts of a polyhydric alcohol ester of a fatty acid and an ester of a tribasic inorg. acid (B) and, if necessary, 0.01-5pts.wt. at least one nitrogen compound selected from among polyamides, triazines and dicyan diamide.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to novel stabilized oxymethylene copolymer compositions. More specifically, the present invention has superior long-term stability, especially long-term hot water resistance and long-term heat aging resistance, compared to conventional oxymethylene copolymer compositions, and has no deposits on the mold during molding. This invention relates to extremely low stabilized oxymethylene copolymer compositions.

BACKGROUND OF THE INVENTION Oxymethylene copolymers are plastics that are widely used in various fields as engineering resins because they have excellent mechanical properties and moldability.

However, this oxymethylene copolymer itself is insufficiently stable, and depolymerization occurs at the terminal end of the polymer.
However, since it has drawbacks such as causing main chain scission in high-temperature atmospheres or hot water, it is usually treated with various terminal treatments and additives such as antioxidants and thermal stabilizers. It is necessary to stabilize it by blending it with

In particular, when the oxymethylene copolymer is used as an engineering resin, it is essential to incorporate a thermal oxidation stabilizer to maintain and improve its quality, and various stabilizers have been proposed so far.

For example, a metal salt of a nitrogen-free organic acid having 2 to 30 carbon atoms and having at least one carboxyl group;
A stabilizer consisting of at least one metal salt of ~30 nitrogen-free alcohols (U.S. Pat. No. 3,4g4,399)
(specification), at least one compound selected from hydroxides, inorganic acid salts, and alkoxides of alkali metals or alkaline earth metals, a nitrogen-containing polymer compound, and a sterically hindered phenol. Agent (Special Publication 56-109
Publication No. 39), etc. have been proposed.

On the other hand, as an antistatic agent for oxymethylene copolymers, borate esters of glycerin heptanofatty acid esters have been proposed (Japanese Patent Publication No. 15616/1983), but these are not necessarily satisfactory as stabilizers.

In addition, as a method of suppressing precipitates on the mold surface during molding, polyamide (U.S. Pat. No. 2.993,0
25 specification, JP-A-50-1454511), nitrogen compounds such as amide compounds or hydrazine compounds (JP-A-57-102943, JP-A-57-1)
Methods have been proposed in which the additives (IN46, JP-A-59-33353, JP-B-Sho 54-0658) are added.

However, when a fatty acid metal salt or aliphatic alcohol metal salt is blended into an oxymethylene copolymer, it is effective in terms of long-term heat aging resistance and long-term hot water resistance, but it has the drawback of significant discoloration. In addition, oxymethylene copolymers containing metal hydroxides, inorganic acid salts, or alkoxides, nitrogen-containing polymer compounds, and sterically hindered phenols have also been shown to have some effect on long-term heat aging properties. If it is kept in hot water for a long period of time, it has the disadvantage of not only causing spots but also decreasing its mechanical strength.

In addition, polyamide, which is effective in preventing precipitation on the mold surface during molding, is effective as a formaldehyde scavenger and suppresses precipitation on the mold surface caused by formaldehyde, but polyamide itself is On the other hand, nitrogen compounds such as amide compounds and hydrazine compounds have less adhesion to molds than polyamides, but they have inferior formaldehyde trapping ability, so they cannot be used with metals. The generation of precipitates on the mold surface cannot be sufficiently suppressed.

Problems to be Solved by the Invention The present invention overcomes the drawbacks of conventional oxymethylene copolymer compositions, has excellent long-term hot water resistance and long-term heat aging resistance, and has excellent resistance to molding during molding. This invention was made for the purpose of providing a stabilized oxymethylene copolymer composition with extremely few precipitates.

Means for Solving the Problems The present inventors have improved long-term heat aging resistance and long-term hot water resistance without impairing the desirable physical properties of oxymethylene copolymers, and have also improved the ability to prevent deposits from forming on molds during molding. As a result of intensive research to develop an oxymethylene copolymer composition that effectively suppresses the occurrence of
The inventors have discovered that the above object can be achieved by blending a specific compound as a stabilizer into an oxymethylene copolymer, and based on this knowledge, they have completed the present invention.

That is, the present invention provides (A) an oxymethylene copolymer, (B) an alkaline earth metal salt of an ester of a polyhydric alcohol monofatty acid ester and a tribasic inorganic acid, and optionally further as a component (C). The present invention provides a stabilized oxymethylene copolymer composition containing at least one nitrogen-containing compound selected from polyamides, triazines, and dicyandiamide.

The present invention will be explained in detail below.

In the composition of the present invention, the oxymethylene copolymer used as component (A) is -maximum→CH2-0+
...(1) An oxymethylene unit represented by the following and -max (R1 in the formula
and R2 are (each a hydrogen atom, an alkyl group, or an aryl group, which may be the same or different, and m is an integer of 2 to 6) It is a copolymer having a structure in which units are randomly bonded, and the ratio of oxyalkylene units is not particularly limited, but it is preferably 0.05 to 5 per 100 moles of oxymethylene units.
The amount is preferably 0 mol, more preferably 0-1 to 20 mol. Examples of the oxyalkylene unit include oxyethylene units, oxypropylene units, oxytetramethylene units, and oxyphenylethylene units. Among these oxyalkylene units, oxyethylene unit +(CH2)20+ and oxytetramethylene unit +(CHz)-0+ are particularly preferred from the viewpoint of improving the physical properties of the oxymethylene polymer.

This oxymethylene copolymer is obtained by copolymerizing or reacting formaldehyde, trioxane, or oxymethylene homopolymer with a cyclic ether or cyclic formal. The oxymethylene copolymer obtained here is desirably subjected to stabilization treatment at the molecular ends.

This stabilization treatment method usually involves -OH at the polymer end.
by esterifying or adding relatively stable carbon to each end.
A method such as hydrolysis is used until carbon bonds are present.

In the composition of the present invention, component (B), that is, an alkaline earth metal salt of an ester of a polyhydric alcohol monofatty acid ester and a tribasic inorganic acid (hereinafter abbreviated as stabilizer) is used as a stabilizer.

The polyhydric alcohols constituting this stabilizer include ethylene glycol, propylene glycol, l, 3-
Propanediol, l,2-butanediol, 1.3-
Dihydric alcohols such as 1,4-butanediol, 1,6-hexanediol, 1,5-bentanediol, trihydric alcohols such as glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, sorbitan, sorbitol, Examples include polyhydric alcohols such as sucrose, styrene glycol, phenyl group-substituted products such as phenylglycerin ether, bisphenols such as bisphenol A, but among these, glycerin, trimethylolethane, and Trihydric or higher polyhydric alcohols such as methylolpropane, pentaerythritol, sorbitan, sorbitol, and mannitol sugar are preferred, and glycerin and sorbitan are particularly preferred.

In addition, examples of fatty acids constituting these polyhydric alcohols and monofatty acid esters include acetic acid, propionic acid,
butyric acid, valeric acid, casillonic acid, capric acid, lauric acid,
Examples include myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, and behenic acid, among which capric acid, lauric acid, myristic acid, balmitic acid, stearic acid, oleic acid, linoleic acid, and behenic acid. Fatty acids having 8 to 22 carbon atoms are preferred, with lauric acid and stearic acid being particularly preferred. Also,
The tribasic inorganic acid constituting the stabilizer is preferably, for example, phosphoric acid or boric acid, and the alkaline earth metal to form a salt includes, for example, alkaline earth metal, calcium, barium, strontium, etc.
Among these, magnesium, calcium and barium are particularly preferred.

Specific examples of the stabilizer include monoborate magnesium salt of ethylene glycol monolaurate, 1, 6
- Monoborate ester calcium salt of hexaneshiol monostearate, monoborate ester luciram salt of glycerin monozropionate, monoborate ester calcium salt of glycerin monostearate, monoborate ester magnesium salt of glycerin monostearate, glycerin monostearate Monoborate ester barium salt of stearate, glycerin, monoborate ester calcium salt of monolaurate, monoborate ester magnesium salt of glycerin monolaurate, monophosphate ester calcium salt of glycerin monostearate, monophosphoric acid of glycerin monostearate Ester magnesium salt, monophosphate ester calcium salt of glycerin monolaurate, monophosphate ester magnesium salt of glycerin monolaurate, monoborate ester calcium salt of glycerin monobehenate, monoborate ester calcium salt of sorbitan monostearate, sorbitan mono Magnesium monoborate ester of stearate,
Sorbitan monostearate monoborate barium salt, sorbitan monolaurate monoborate calcium salt, sorbitan monolaurate monoborate magnesium salt, sorbitan monolaurate monoborate barium salt, sorbitan monolaurate monoline acid ester calcium salt, monophosphate ester magnesium salt of sorbitan monolaurate,
Examples include monophosphate barium salt of sorbitan monolaurate. These stabilizers may be used alone or in combination of two or more.

There are no particular restrictions on the method for producing the stabilizer, but for example, a tribasic inorganic acid is added to a polyhydric alcohol monofatty acid ester, heated to remove condensation water, and then the resulting compound is dissolved in an appropriate solvent. After dissolving, the desired product can be obtained by neutralizing it with an alkaline earth metal hydroxide, or by mixing an alkaline earth metal salt of a tribasic inorganic acid with a polyhydric alcohol monofatty acid ester and heating it. Examples include methods of condensation (Japanese Patent Publication No. 14322-1983, Japanese Patent Publication No. 14322-1989,
43371).

The amount of the stabilizer in the composition of the present invention is usually 0.01 to 5 parts by weight, preferably 0.03 to 1 part by weight, and more preferably 0.05 to 1 part by weight, based on 100 parts by weight of the oxymethylene copolymer. It is selected within a range of 0.5 parts by weight. If this amount is less than 0.01 part by weight, the effect of improving long-term heat aging resistance and long-term hot water resistance and the effect of suppressing the generation of precipitates in the mold during molding will not be sufficiently exhibited.
If it exceeds 1 part by weight, silver streaks or residual coloration tend to occur during injection molding, which is not preferable.

In the composition of the present invention, in order to further enhance the effect of suppressing the generation of precipitates in the mold during molding, as desired, component (C) may be selected from polyamides, triazines, and dicyandiamide. At least one nitrogen-containing compound can be blended.

The polyamides are high molecular weight compounds having a bond represented by -max (in the formula, R is a hydrogen atom or an alkyl group) in the molecular chain, and as such,
For example, polymers from lactams such as caprolactam and laurolactam, dicarboxylic acids such as dimers of adipic acid, sebacic acid, dodecanoic acid, and linoleic acid, and ethylenediamine, tetramethylenediamine, hexamethylenediamine, metaxylylenediamine, etc. Polymers obtained by reaction with diamines, poly-β-alanine (JP-A-59-2N722, JP-A-59-2N752), copolymers of these polymers, and the like are used. Specifically, nylon 6.12.46.66.610, l11
2, poly(xylylene adipamide), etc.

Further, as the triazines, for example, melamine, acetoguanamine, acryloguanamine, etc. are used.

One type of these nitrogen-containing compounds may be used, or two or more types may be used in combination. Furthermore, among the nitrogen-containing compounds, polyamides are preferred.

In the composition of the present invention, the amount of the nitrogen-containing compound as component (C) is usually 0.01 to 5 parts by weight, preferably 0.01 parts by weight, based on 100 parts by weight of the oxymethylene copolymer.
-1 part by weight, more preferably from 0.05 to 0.5 part by weight.

The composition of the present invention may further contain an antioxidant commonly used in oxymethylene copolymer compositions. As this antioxidant, sterically hindered phenols and sterically hindered amines are used, 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-(-hydroxyphenyl)propionate], 1,6-hexanethiolubis[3-(3,S-di-t-butyl-4-hydroxyphenyl)propionate ], phenols such as distearyl-3,5-di-butyl-4-hydroxybenzylphosphonate, and 3,5-di-t-butyl-4-hydroxyphenyl-3,5-distearyl-thiotriazylamine. , N-phenyl-N'-inpropyl-p-7
22-diamine, N,N'-diphenyl-p-phenylenediamine, 4,4'-bis(4-α,α-dimethylbenzyl)diphenylamine, N,N'-di-β-naphthyl-p-phenylenediamine Amines such as can be used. Among these antioxidants, especially 2.2
'-methylene-bis(4-methyl-6-t-7' tylphenol), triethylene glycol-bis[3-(3
-t-butyl-5-methyl-4-hydroxyphenyl)
propionate], pentaerythrityl-tetrakis [
3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] is effective.

In the composition of the present invention, there is no particular restriction on the order in which the above-mentioned components are added to the oxymethylene copolymer of component (A). Moreover, there is no particular restriction on the shape of each of the above-mentioned components to be blended, and they may be in the form of powder, liquid, or solution.

The composition of the present invention may contain other additives that are usually added to oxymethylene copolymer compositions, such as antistatic agents, lubricants, inorganic fillers such as glass fibers and glass pieces, and reinforcing materials such as carbon fibers. , pigments, etc. can be blended as desired.

Effects of the Invention By adding a stabilizer to the oxymethylene copolymer, the oxymethylene copolymer composition of the present invention has better long-term heat aging resistance at +40°C than conventional oxymethylene copolymer compositions. In the 120°C long-term hot water resistance test, the tensile strength, elongation, and weight retention were significantly improved, and there was very little change in the appearance of the test molded product. moreover,
When continuous molding is carried out, compared to conventional oxymethylene copolymer compositions, the occurrence of precipitates in the mold is extremely small, and the appearance of the molded product is also good.

Although it is not necessarily clear that this improvement in property retention in long-term properties is due to the fact that the alkaline earth metal salt contained in the stabilizer acts effectively as a receptor for the formic acid generated by the thermal decomposition of the oxymethylene copolymer. This is thought to be due to the fact that Furthermore, hydroxides and oxides of alkali metals and alkaline earth metals act as catalysts for formose production, whereas stabilizers are less likely to act as catalysts for formose production.
This is thought to have an effect on the improvement in physical property retention. Furthermore, the reason why there is little occurrence of precipitates on the mold during continuous molding is thought to be that the stabilizer suppresses the adhesion of formaldehyde gas to the mold surface. Furthermore, the addition of the nitrogen-containing compound synergistically suppresses the generation of the precipitate.

Due to these factors, the oxymethylene copolymer composition of the present invention can withstand harsh environments such as high temperatures and hot water for a long period of time, and can also withstand long-term continuous molding. The generation of precipitates is small and can greatly contribute to improving productivity.

EXAMPLES Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way.

In addition, each characteristic of the composition in an Example and a comparative example was calculated|required as follows.

(1) Long-term hot water environment test A hot water resistance test was conducted at 120°C using an autoclave equipped with a pressure regulating valve. However, the test water used was ion-exchanged water, and the temperature adjustment device and flow meter were set at 120°C.
It was done using the running water method.

Regarding the evaluation, for the initial molded product and the molded product after retention,
Tensile strength (according to ASTtll D-6311), tensile elongation (according to ASTM D-638), weight (10+g
The retention rate (measured in units) and the degree of change in the appearance of the molded product were determined.

(2) Change in external appearance of molded products The changes in appearance of the initial molded products and the molded products after residence were visually observed and evaluated according to the following criteria.

Judgment criteria ○: A slight change in color tone is observed with the naked eye.

Δ: Yellowing is clearly observed with the naked eye.

Alternatively, pockmark patterns are observed here and there on the surface of the molded product.

×: Brown discoloration is observed. Or, a pock pattern is observed all over the surface of the molded product.

(3) Long-term hot air environmental test gear oven [manufactured by Tabai Seisakusho Co., Ltd., GPS-22]
A long-term hot air environment test at 140'C was conducted using Type 2, exhaust duct opened at 20 degrees. The evaluation items and methods are the same as the long-term hydrothermal environmental test.

(4) Evaluation by continuous molding test Injection molding machine Nikko N? OA (manufactured by Nippon Steel Corporation)
Cylinder temperature 200℃ Injection pressure 40kg/cmG injection
Time: 5 sec Cooling: 5 sec Mold Temperature: 90'O and 30°C J under the above molding conditions
After continuous molding of the IS-3 tensile test piece for 5,000 shots, the condition of the gold precipitate was observed with the naked eye and evaluated according to the following criteria.

Judgment criteria 0: Mold deposit is not recognized at all.

1: Almost no mold deposit is observed.

2: The mold deposit is found to be dull.

3: Mold deposit is clearly recognized.

4: Mold deposit is thickly attached to the entire surface of the mold.

(5) Change in appearance of molded product after retention in molding After retaining the material in an injection molding machine (H1-55-2S [l, manufactured by Arburg) at a temperature of 230°C for 1 hour, a test piece with a shape of approximately 3 x 12 x 120 mm was observed. Short flakes were molded, and the extent of silver streaks in the molded product was observed and evaluated according to the following criteria.

Judgment criteria O: No silver streaks or yellowing are observed on the surface of the molded product.

Δ: Silver streaks are partially observed on the surface of the molded product.

Alternatively, yellowing of the molded product is observed.

×: Silver stripes are observed on the entire surface of the molded product.

Or yellowing of the molded product is clearly and strongly observed.

In addition, the symbols in the table indicate the following.

Stabilizer G-1: Monoborate ester calcium salt of glycerin monostearate G-2: Monoborate ester magnesium salt of glycerin monostearate G-3 = Monoborate ester calcium salt of glycerin monolaurate G-4: Glycerin monostearate Monophosphate ester calcium salt of stearate G-5: Monophosphate ester magnesium salt of glycerin monolaurate G-6: Monoborate ester barium salt of glycerin monostearate G-7: Monoborate ester calcium salt of sorbitan monostearate G-8: Monophosphate ester calcium salt of sorbitan monostearate G-9: Monoborate ester barium salt of sorbicun monolaurate G-10: Monoborate ester calcium salt of glycerin monopropionate G-11: Ethylene glycol Magnesium monoborate ester of monolaurate G-12: 1,6-hexanesiol Monoborate calcium salt of monostearate G-13 + monoborate calcium salt of glycerin monobehenate Antioxidant A-1: h-lyethylene Glycolubis[3-(3-tert-butyl-5-methyltohydroxyphenyl)propionate] (trade name Coil Ganox 245 (manufactured by Ciba Geigy)) A-2: Pentaerythrityl-tetrakis[3-(3°) 5-C-tert-butyl-4-hydroxyphenyl)propionate] (trade name: Nylganox 1)
010 (manufactured by Ciba Geigy)) A-3: 2.2'-methylene-bis(4-methyl-6-tert-butylphenol) (trade name: Yoshinox 2246 (manufactured by Yoshitomi Pharmaceutical)
) Nitrogen-containing compound C-1: Nylon 66 C-2: Nylon 6/66/61G (40%/30%/
30%) C-3 = Poly-β-alanine C-4 = Melamine C-5 Nidicyandiamide Other stabilizers D-1 = Monoborate ester of glycerin monostearate D-2 = Calcium stearate D-3: Calcium ricinoleate D-4: Calcium hydroxide D-5 = Monoborate sodium salt of glycerin monostearate Production example Production of oxymethylene copolymer 98% by weight of trioxane and 2% by weight of ethylene oxide were combined into a boron-butyl ether complex containing 98% by weight of trioxane and 2% by weight of ethylene oxide. was used as a catalyst to obtain a crude oxymethylene copolymer, triethylamine was added to this to stop the reaction, and the polymer was separated. A triethylamine-water mixture was then added to the polymer and the terminal instability was removed in a vented 651 extruder. Ml of the polymer after terminal stabilization is 9.5
(g/10 minutes). This polymer is designated as B-1.

Also, 97% by weight of trioxane and 3% by weight of 1.3-
An oxymethylene copolymer [Ml9.0 (9/
10 minutes)] was obtained. This polymer is designated as B-2.

Examples 1 to 36, Comparative Example 1-11 The compositions shown in Tables 1 to 4 were mixed homogeneously using a Henschel mixer, the mixture was passed through a 50I extruder, melted and stabilized, and the resin was stranded from the die head. Obtained. The strands were immediately made into pellets, and after drying, each evaluation was performed. The results are shown in Tables 1 to 4.

Claims (1)

[Scope of Claims] 1. A stabilized oxymethylene copolymer obtained by blending (A) an oxymethylene copolymer with (B) an alkaline earth metal salt of an ester of a polyhydric alcohol monofatty acid ester and a tribasic inorganic acid. Methylene copolymer composition. 2 0.0 parts by weight of component (B) per 100 parts by weight of component (A)
The composition according to claim 1, comprising 1 to 5 parts by weight. 3 (A) oxymethylene copolymer, (B) alkaline earth metal salt of ester of polyhydric alcohol monofatty acid ester and tribasic inorganic acid, and (C) among polyamides, triazines, and dicyandiamide. A stabilized oxymethylene copolymer composition comprising at least one nitrogen-containing compound selected from the following. 4 0.0 parts of component (B) per 100 parts by weight of component (A)
The composition according to claim 3, comprising 1 to 5 parts by weight of component (C) and 0.01 to 5 parts by weight of component (C).