JPS6054346B2 - Polyacetal resin composition with improved mold deposit and thermal stability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel polyacetal resin composition with improved mold deposit and thermal stability, and more particularly:
A resin composition containing melem in polyacetal resin,
The present invention also relates to a resin composition in which a polyacetal resin contains the melem and a polyamide resin.

Polyacetal resin is mainly used in metal replacement fields where toughness, oil resistance, solvent resistance, creep resistance, etc. There is.

Therefore, polyacetal resins are required to have extremely strict quality. By the way, polyacetal resin cannot be sufficiently prevented from decomposition (formaldehyde gas generation) by simply stabilizing the terminal ends and adding an antioxidant, and therefore In order to prevent silver streaks (also called silver streaks, traces of gas running) that appear on molded products, as well as problems with molding stability, dimensional stability, and strength, it is necessary to incorporate heat stability into the product. .

Hitherto, polyamide resins, amide compounds, urea derivatives, hydrazine derivatives, sulfur compounds, polysaccharides, etc. have been proposed as heat-stable materials. Disadvantages such as discoloration to yellowish brown due to the action of oxygen, blackish brown scorching on the screw, or fine particles adhering to the inside of the mold (mold deposit) resulting in loss of gloss on the surface of the molded product. , and its improvement has been strongly desired.

The present inventors have conducted extensive research to overcome these drawbacks and provide a polyacetal resin composition with excellent thermal stability. As a result, a resin composition containing a predetermined amount of melem in a polyacetal resin has been developed. being able to achieve that purpose;
It was discovered that a resin composition containing a predetermined amount of the above-mentioned melem and polyamide resin in a polyacetal resin can achieve the object due to a synergistic effect, and based on this knowledge, the present invention was completed. Ivy.

That is, the present invention provides a mold deposit characterized by containing 0,001 to 2 parts by weight of melem represented by the formula per 100 parts by weight of the polyacetal resin, and a polyacetal resin composition with improved thermal stability. Furthermore, per 100 parts by weight of polyacetal resin,
A mold deposit and a polyacetal resin composition with improved thermal stability, characterized by containing 0,001 to 2 parts by weight of melem represented by the above formula (1) and 0.01 to 1 part by weight of a polyamide resin. It provides:

The polyacetal resin used in the composition of the present invention is a polymer obtained by homopolymerization of formaldehyde or its cyclic oligomers such as trioxane or tetraoxane, or by copolymerization with a comonomer copolymerizable with these. In order to prevent depolymerization from the ends, the ends are stabilized by esterification or urethanization in the case of homopolymers, and by thermal decomposition of unstable ends in the case of copolymers. It is something.

On the other hand, melem used as a thermal stabilizer in the composition of the present invention is a weakly basic compound having the structure of formula (1) obtained by calcination of urea, and has no melting point and is difficult to thermally decompose. (Loss loss: 1.8% when heated at 300°C for 100 hours), and is almost insoluble in water and organic solvents.

The content of melem in the composition of the present invention ranges from 0,001 to 2 parts by weight, preferably from 0.01 to 0.5 parts by weight, per 10 parts by weight of polyacetal resin. If the content is less than 0.001 parts by weight, the effect as a heat stabilizer will not be achieved, and if it exceeds 2 parts by weight, the action of the base may become strong and promote thermal decomposition, which is not preferable. In the composition of the present invention, other heat stabilizers, such as polyamide resins, amide compounds, urea derivatives, polysaccharides, cellulose, etc., or antioxidants, light stabilizers, and lubricants that have a low decomposition effect on polyacetal resins may be used. etc. can also be added.

In particular, when the above-mentioned melem and polyamide resin are used in combination, their synergistic effect provides excellent effects in preventing thermal decomposition, preventing screw scorching, and improving mold deposits. In this case, the contents of melem and polyamide resin are each 0.0 parts per 10 parts of polyacetal resin.
It is necessary that the amount is in the range of 0.01 to 2 parts by weight, and 0.01 to 10 parts by weight.

In addition, in the composition of the present invention, other additives commonly used in polyacetal resins, such as glass fibers, inorganic fillers, carbon fibers, pigments, polymers,
Lubricating oil and the like may also be added.

In the composition of the present invention, the polyacetal resin and the heat stabilizer can be mixed by a commonly used melt-mixing method, and when used in combination with other compounding agents, they may be melt-mixed at the same time. You can.

Note that the heat stabilizer is more effective when dispersed in fine powder, so it is best to use it by pulverizing it to the microscopic level, or
It may be blended with 0 to 100 times the amount of polyacetal resin, extruded, pelletized, freeze-pulverized to prepare a masterbatch, blended again with terminal-stabilized polyacetal resin, extruded, and pelletized.
In this case, the extrusion temperature is preferably in the range of 180 to 20 (temperatures). Although the thermal decomposition prevention effect is slightly inferior to polyacetal resin compositions containing polyacetal resin, there are no problems in practical use. Melem's heat resistance, discoloration resistance, formaldehyde absorption, and mold releasability exhibit excellent effects in terms of mold deposits (adhesion of foreign matter to the inner surface of the mold), etc. Due to their synergistic action, the polyacetal resin composition of the present invention containing melem and polyamide resin not only exhibits excellent effects in terms of retention discoloration in cylinders, scorching on screws, and mold deposits, but also in heat resistance. It also exhibits excellent effects in preventing decomposition.

Next, the present invention will be explained in more detail with reference to Examples.

The thermal stability of the resin composition was evaluated by examining the amount of gas generated, retention discoloration, occurrence of scorching, and occurrence of mold deposit (hereinafter abbreviated as MD) according to the following method.

Sample pellet 1 in a cocked syringe with a gas generation volume of 20 ml
．． After inserting an aluminum boat loaded with 0g and inserting a cylinder moistened with heat-resistant silicone oil, the air inside was replaced with nitrogen 15 times, and then immersed in a silicone oil bath at 230°C, and the actual volume was heated for 2 minutes. Gas generation amount S (ml/g
).

Retention discoloration* Put 500 m9 of pellets into a test tube with a diameter of 8 mm,
After heating the powder in a silicone oil bath at 230°C, it was rapidly cooled and the color rank at that time is also expressed.

Color rank ◎ White A Pale yellowish brown Δ × ×× Brown burnt occurrence and immediate occurrence Using a 1 oz injection molding machine, cylinder temperature 200°C
In continuous injection molding at a mold temperature of 80° C., represents the number of days until minute burns occur on the surface of the molding machine screw, and the number of moldings until the surface of the molded product begins to lose its luster due to MD occurrence.

Examples 1 to 7, Comparative Examples 1 to 7 Powdered terminal acetylated polyacetal homopolymer (HO) or copolymer of trioxane and ethylene oxide (weight ratio 100:2) whose unstable terminals were decomposed by heat treatment (CO) 100 parts by weight, melem finely ground in a ball mill and antioxidant 2,
0.25 parts by weight of 2″-methylenebis(4-methyl-6-Tert-butyruphenol) was blended and heated to 190′C.
It was extruded and pelletized.

After drying this at 80°C for H hours, a thermal stability test was conducted. The results are shown in Table 1. As is clear from Table 1, the resin composition containing melem is slightly inferior in anti-decomposition property compared to the resin composition containing polyamide resin, but it is within a range that does not cause any practical problems, and the retention It can be seen that it is far superior in terms of discoloration, scorching, and mold deposits.

Examples 8 and 9 Polyamide heat stabilizer (Ny6/Ny66/Ny6lO
The thermal stability of the polyacetal resin composition containing melem (=60/20/20) was evaluated.

The results are shown in Table 2. As is clear from Table 2,
It can be seen that the system in which a polyamide heat stabilizer and melem are combined is superior to the system using only polyamide in all aspects of thermal decomposition, retention discoloration, scorching, and mold deposit.

Claims (1)

[Claims] 1. Per 100 parts by weight of polyacetal resin, formula ▲ mathematical formula,
There are chemical formulas, tables, etc. Melem represented by ▼ 0,00
A polyacetal resin composition having improved mold deposit and thermal stability, characterized in that it contains 1 to 2 parts by weight. 2 Per 100 parts by weight of polyacetal resin, formula ▲ formula,
There are chemical formulas, tables, etc. Melem represented by ▼ 0,00
A polyacetal resin composition having improved mold deposit and thermal stability, characterized in that it contains 1 to 2 parts by weight of a polyamide resin and 0.01 to 10 parts by weight of a polyamide resin.