JPS59213752A - Polyacetal composition - Google Patents

Abstract

PURPOSE:The titled composition having improved heat stability during molding and processing, suppressing formation of deposit materials in a mold and die, and causing low coloring in molded or processed article, obtained by blending polyacetal with finely divided powder of poly-beta-alanine. CONSTITUTION:100wt% polyacetal is blended with 0.01-0.5wt finely divided powder (<= about 5 micron particle diameter) of poly-beta-alanine. Polyoxymethylene diacetate is used as the polyacetal. Preferably 0.01-5wt% antioxidant of bisphenol is further used together.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polyacetal composition to which poly-β-alanine fine powder is added as a heat stabilizer.

Polyacetal resins are obtained by polymerizing formaldehyde or its cyclic oligomers, trioxane or tetraoxane, or by copolymerizing them in the presence of copolymerizable monomers and then decomposing them from the terminal groups of one polymer. In order to prevent polymerization, end group treatment is performed by various methods such as etherification and esterification, and then an antioxidant, a light stabilizer, a lubricant, etc. are added to the molding composition, which is known as a molding composition.

In the production of polyacetal resin, the addition of a heat stabilizer together with the terminal group treatment reaction is a necessary and important factor for maintaining and improving its quality, and various ideas and proposals have been made in the past.

For example, it is described that urea or its derivatives, hydrazine or its derivatives, amides, polyamides, sulfur compounds, and a wide variety of other substances should be used alone or in combination with antioxidants, ultraviolet absorbers, and the like. Although these numerous proposals certainly have some stabilizing effect,
For example, during the molding process of polyacetal, some low molecular weight stabilizers cause evaporation and bleeding after molding, resulting in a significant decrease in the stabilizing effect, and the stabilizing effect is not sustainable. However, there were very few proposals that could be put into practical use.

Of these, 35 units of hexamethylene aziboamide, 27 units of hexamethylene cepacoamide, and 38 units of caprolactam.
A terpolymer consisting of 1 is a type of stabilizer that can be put to practical use because it exhibits a good thermal stabilizing effect among polyamides and is durable (Japanese Patent Publication No. 34-5440).

However, even the copolyamides exhibiting the excellent performance described above still have major deficiencies. One of them is coloring when subjected to the joint action of heat, light or oxygen, which is compounded into polyacetal and during the molding process of the compound.
Or it may cause discoloration over time, significantly reducing the quality of the product. That is, when processing synthetic resins, it is common to carry out remolding in order to increase molding efficiency.

Re-molding parts such as runners in injection molding, failed molding products, and damaged products. At this time, it is desirable that the quality of the product remains unchanged, but polyacetal containing copolyamide has a significant degree of coloring.

Not only discoloration during such a molding process but also discoloration of the molded product over time is observed.

Therefore, even though copolyamide-based heat stabilizers have a satisfactory thermal stabilizing effect, they still have serious defects, and compared to polyacetal compositions in which copolyamide does not coexist, The disadvantages in terms of discoloration are difficult to overcome. Furthermore, during molding or extrusion using a polyacetal composition containing a copolymerized polyamide as a heat stabilizer, buildup occurs in the mold and die in a relatively short period of time, making it difficult to clean the mold and die. known to be necessary. Furthermore, JP-A-53-78255 discloses that polyhexamethylene adipamide is dispersed in ethylene/methyl acrylate resin to prepare a polyamide/carrier resin mixture and used as a heat stabilizer for polyacecool. There is. However, when the above-mentioned heat stabilizer is used, the performance of preventing discoloration during molding and suppressing the formation of deposits on a mold or die is still insufficient.

The present inventors have conducted intensive research to overcome the above-mentioned drawbacks and to obtain a polyacetal composition having an even better stabilizing effect.As a result, a polyacetal composition containing polyβ-aniline has been developed. discovered that it is possible to obtain a composition that overcomes the above-mentioned problems, and completed the present invention.

That is, one aspect of the present invention is a polyacetal composition "t'il" which is prepared by mixing fine powder of poly-β-aniline.

The polyacetal composition of the present invention has high thermal stability during molding, has the ability to suppress the formation of mold or die deposits, and has the following effects of less coloring of molded products. The present invention will be explained.

Polyβ-alanino used in the present invention is obtained by hydrogen transfer polymerization of acrylamide. As the catalyst, an alkali metal alcoholade or an alkaline earth metal alcoholade is used.

Examples of the solvent used in the reaction include 0-dichlorobenzene, xylene, and nitrobenzene.

The reaction temperature is usually 60'C or higher. If it is below 60°C, the polymerization rate will be slow, which is preferable.

The amount of catalyst used in the reaction is 0.02 mol or more per 1 mol of acrylamide. If the amount is less than 0.02 mol, the reaction rate decreases, the single polymerization yield becomes low, and vinyl polymer (polyacrylamide) is less likely to be produced, which is not preferable.

The amount of solvent used is such that the acrylamide concentration in the charged reaction solution is 5.
A range of ˜20 inches is preferred. If the acrylamide concentration is less than 5% or more than 20%, the polymer yield will decrease, which is not preferable.

The polymer obtained by the above method is separated from the solvent in a furnace and purified into a fine powder. For example, after dissolving in water, it can be purified and pulverized by reprecipitation in methanol, acetone, etc. The poly-β-alanine fine powder thus obtained has a particle size of about 5 microns or less and can be used as a heat stabilizer for polyacetal resin.

In the present invention, it is possible to use an antioxidant together with the above-mentioned poly-β-alanine, and it provides favorable results. As antioxidants, aromatic amines, phenols,
In particular, the effects of phenols, especially bisphenols, are remarkable. Examples include alkyl-substituted phenols, cresols, alkyl-substituted hydroquinones, alkylidene bis-alkyl-substituted phenols, and the like.

The amount of poly-β-722 used in the present invention is in the range of 0.01 to 0.5% by weight based on 200% by weight of polyacetal. Further, the antioxidant is used in an amount of 0.01 to 5% by weight based on 100% by weight of the polyacetal.

As mentioned above, the boria tar to which the present invention is applied is a polyacetal or copolymer prepared by terminal-stabilizing polyoxymethylene synthesized from formaldehyde or its cyclic oligomer, or a copolymer with a comonomer that can be copolymerized with the same. It is emphasized that it is useful for polyacetals, especially polyoxymethylene diacetate.

The method for producing the polyacetal composition of the present invention is as follows.

In order to disperse the heat stabilizer as uniformly as possible, a powdered polyacetal resin is used to mix poly-β-alanine powder and, if necessary, antioxidant powder. As the mixing device, an electric mixer such as a Henschel mixer can be used. Next, use an extruder to 180℃~200℃
The above mixed powder can be extruded into pellets at a temperature of .

This will be explained below by giving examples.

Example-1 200 m of 0-dichlorobenzene was placed in a 300 tnt flask equipped with a stirrer, 1.4 Sl of calcium propylade was added as a catalyst, and 20.0 ml of acrylamide was well dispersed in the solvent. Of was added thereto, and the mixture was reacted at 120° C. for 4 hours while stirring in a nitrogen stream. After the reaction was completed, the solvent O-dichlorobenzene was removed, and 200% of water was added to the polymer, followed by heating under reflux for 2 hours to obtain a homogeneous transparent solution. This polymer solution was dropped into methanol, and the precipitated polymer was separated in a furnace, washed with methanol, and then dried at 60°C. The yield was 14.4 f. The infrared absorption spectrum confirmed that the product was poly-β-alanine. 1 t of formic acid solution at 35℃
The reduced viscosity of the product was 3.7. The particle size of the product was about 5 microns or less as observed by optical microscopy.

Next, 100 parts of a powdered terminal acetylated polyoxymethylene resin and an antioxidant (2,2'-methylenebis(4-methyl-6-t-butylphenol)) were added.
0.25 parts and poly β-alanine o synthesized above
, i part were mixed and extruded at 190° C. using an extruder and pelletized. This was dried with hot air at 80° C. for 14 hours, and a thermal stability test was conducted using the evaluation method shown below. The results are shown in Table-1.

Weight loss rate after 30 minutes [H] Thermal analyzer [Daini Seikodai, SSc-560GI (TG
A sample of 5019 (3 pellets) was placed in a container (3 pellets) and heated at 230° C. in a nitrogen stream, and the weight loss rate was measured after 30 minutes.

Retention discoloration The color of the test piece is expressed by two inks when it is heated to 230°C in a cylinder and retained for 20 minutes in a 1 oz injection molding machine.

Rank AB CDE White, light tan, with brown burnt,
As well as mold deposit (MD) generation using a 1 oz injection molding machine, the cylinder temperature is 200
In continuous injection molding at a metal temperature of 80°C, the number of days until minute burns occur, mold deposits (MD), and the number of moldings until the surface of the molded product loses its luster due to the occurrence of mold deposits (MD).

For comparison, hexamethylene adipamide 1. Ternary copolymer polyamide of hexamethylene sepacoamide and caprolactam (Comparative Example 1)
) and hexamethylene aziboamide dispersed in ethylene and methyl acrylate copolymer (Comparative Example 2). This was subjected to the same thermal stability test as above. Table the results.
Shown in 1.

Table 1 - (Note 1) Addition amount 0.1 part (Note 2) Addition amount As posiamide 0.11 Patent applicant Asahi Kasei Kogyo Co., Ltd.: Procedural amendment (voluntary) ■ June 2, 1982, l! Mr. Kazuo Wakasugi, Commissioner of the Japanese Patent Office±1. Display of the case Showa S8 patent application No. 8662
9 No. 2 Name of the invention Polyacetal composition a Relationship to the case of the person making the amendment Patent applicant 1-2-6 Dojimahama, Kita-ku, Osaka-shi, Osaka Prefecture Subject of amendment & Contents of amendment (1) Application specification No. 4 "Poly-noaniline" in lines 14-15 and 19 of the page is corrected to "poly-β-alanine".

that's all

Claims (1)

[Claims] Polyacetal composition made by mixing fine powder of poly-β-alanine