JPS5933352A - Polyacetal resin composition having improved thermal stability and freed from problem of mold deposit - Google Patents

Abstract

PURPOSE:To provide the titled compsn. which does not suffer discoloration nor deterioration during molding and is freed from deposition of fine powdered materials on the inner surface of a mold, by incorporating a specified polyalkylsiloxane in a polyacetal resin. CONSTITUTION:A polyalkylsiloxane having at least one functional group of formulas I , II, III, IV and V (wherein R1 is a 1-10C alkylene; R2 is a 1-10C alkyl) such as a compd. of formula VI (wherein X is -NH2, -NHR2, -CN, etc.; R2 is a 1-5C alkyl; l is 5-500) is used as a heat stabilizer. 0.005-5pts.wt. said polyalkylsiloxane is blended with 100pts.wt. polyacetal resin. Pref. 0.01-10pts.wt. polyamide resin is used together.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to novel polyacetal resin compositions with improved thermal stability and mold deposits, and more particularly:
The present invention relates to a resin composition in which a polyacetal resin contains a special polyalkylsiloxane, and a resin composition in which a polyacetal resin contains the above-mentioned polyalkylsiloxane and polyamide resin.

Polyacetal resin is mainly characterized by its toughness, oil resistance, and
It is used in metal replacement fields that require solvent resistance and creep resistance, and is used, for example, as mechanical parts and exterior parts of automobiles, electrical products, and machinery. Therefore, polyacetal resins are required to have extremely high quality.

By the way, polyacetal resin cannot be sufficiently prevented from thermal decomposition (formaldehyde gas generation) simply by stabilizing the ends and blending it with an antioxidant.
Therefore, due to this thermal decomposition, streaks (also called silver streaks, where gas has run) that appear on molded products,
In order to prevent problems with molding stability, dimensional stability, strength, etc., it is necessary to incorporate a heat stabilizer.

Hitherto, polyamide resins, amide compounds, urea derivatives, hydrazine derivatives, sulfur compounds, polysaccharides, etc. have been proposed as heat stabilizers, but polyacetal resin compositions containing these have been proposed in the cylinder of a molding machine. The molded product may turn yellowish brown due to the action of heat or oxygen, or there may be blackish brown marks on the screw, or there may be fine powder on the inside of the mold (=J deposit). It has drawbacks such as lack of luster on the surface.
Improvement was strongly desired.

The inventors of the present invention have conducted intensive research to overcome these drawbacks and provide a polyacetal resin composition with excellent thermal stability. It is believed that a resin composition obtained by adding a predetermined amount of the polyargylsiloxane and polyamide resin to a polyacetal resin achieves the object due to a synergistic effect. Based on this finding, we have completed the present invention.

Zunawaji, the present invention is based on the general formula % formula % (9 per 100 parts by weight of polyacetal resin) (in the formula, R1 is an alkylene group having a straight chain or branched chain having 1 to 1 o carbon atoms, and R2 is an alkylene group having 1 to 1 carbon atoms). Polyalkylsiloxane having at least one functional group represented by 1o linear or branched argyl group 0,00
The present invention provides a polyacetal resin composition with improved thermal stability and mold deposit characterized by containing 5 to 5 parts by weight of polyacetal resin i.
0.0 of the above polyalkylene loxane per part by weight
The present invention provides a polyacetal resin composition with improved thermal stability and mold deposit, characterized in that it contains 0.05 to 5 parts by weight and 0.01 to 10 parts by weight of a polyamide resin.

The polyacecool resin used in the composition of the present invention is
A homopolymer obtained by homopolymerization of formaldehyde or its cyclic oligomers trioxane or tetraoxane, or copolymerization with a comonomer copolymerizable with these, in which the homopolymer is used to prevent depolymerization from the terminal end. The terminus of a copolymer is stabilized by esterification or urethanization, or in the case of a copolymer, by thermally decomposing the unstable terminus.

The polyargylene loxane used in the composition of the present invention has the general formula % (in the formula, R1 is a straight or branched alkylene group having 1 to io carbon atoms, and R2 is an alkylene group having 1 to 10 carbon atoms). At least one functional group represented by a linear or branched alkyl group is preferably 0 on a molar basis with respect to silicon.
．． The polymerization degree is 5 to 100%.
It is desirable that it be within the range of ~500.

This polyalkylsiloxane has the general formula X-R,
-8yo(OR4)3 (R5 and R4 in the formula are monoalkyl groups with 1 to 5 carbon atoms,
or -NH2, -NHR2, -0ONI-T2, -0O
NH-R2 or -ON, R1 and R2 have the same meanings as above) alone or in mixtures with water, or with OH type polydialkylsiloxane at both ends or one end, alone or in mixtures. It is obtained by heating and causing a dealcoholization (R40H) reaction, and its general formula is expressed, for example, as follows.

X X X
I I1 Y-8-R-X qnon [Z in the formula (hydroxyl group, alkyl group having 1 to 10 carbon atoms, or -NH2, -NHR, -aoNH2, -0ONT(
J-ON-containing alkyl group having 1 to 10 carbon atoms (where R is an alkyl group having 1 to 5 carbon atoms), Y is a hydroxyl group or an alkyl group, or both, A, m, n and p are amino satisfies the conditions that the sum of one or more of groups, amide groups, and cyanogen groups is 0.5 to 100 on a molar basis with respect to silicon, and the overall degree of polymerization is 5 to 500. (Arbitrary integers, R1, R3 and It is desirable that the ratio is between 5 and 100%, and the ratio is preferably between 2 and 100%. Preferably, the degree of polymerization is preferably in the range of 5 to 500, particularly preferably in the range of 10 to 200. If the degree of polymerization is too low, the anti-thermal decomposition properties tend to decrease, and if the degree of polymerization is too large, problems such as poor compounding operability will occur.

The content of polyalkylsiloxane in the composition of the present invention is 0.00 parts by weight per 100 parts by weight of polyacetal resin.
For 5 to 5 layers, the amount is 1 part, preferably 0.02 to 2 parts by weight. In particular, in the case of amine group-containing polyalkylsiloxane, if the content is too large, it may have a negative effect on the thermal decomposition prevention property, so the content should be 0.02 to 0.
．． Particularly suitable is the range of 5-layered parts.

In the composition of the present invention, other heat stabilizers, such as polyamide resins, amide compounds, urea derivatives, polysaccharides, cellulose, etc., or antioxidant 1]-agents and light stabilizers that have a low decomposition effect on polyacetal resins are used. , a lubricant, etc. may also be added.

In particular, when the above-mentioned polyalkylsiloxane and polyamide resin are used in combination, their synergistic effect provides excellent effects in preventing thermal decomposition, preventing scorching of the screw, and improving mold deposits.

In this case, the contents of polyalkylsiloxane and polyamide resin need to be in the range of 0.005 to 5 parts by weight and 0.01 to 10 parts by weight, respectively, per 100 parts by weight of polyacetal resin.

Indeed, 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 polyacecool 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. good. The heat stabilizer is more effective when microdispersed, so it can be used after being pulverized to the microscopic level, or it can be blended with 10 to 100 times the amount of polyacecool resin and extruded into pellets.
Thereafter, the masterbatch may be prepared by freezing and pulverizing, and this may be blended with a terminal-stabilized polyacetal resin, extruded, and pelletized. In this case, the extrusion temperature is preferably in the range of i,so to 200°C.

The polyalkylsiloxane used in the present invention is a new heat stabilizer, and the polyacetal resin composition of the present invention containing it is a polyacetal resin composition containing a conventional heat stabilizer, such as a polyamide resin. Compared to resin compositions, the thermal decomposition prevention effect is slightly stronger, but there are no practical problems, especially discoloration due to retention in the cylinder (browning), scorching on the screw (causing black spots on molded products), mold It exhibits excellent effects in terms of deposits (adhesion of foreign matter to the inner surface of the mold), etc.

In addition, the polyacetal resin composition of the present invention containing polyalkylsiloxane and polyamide resin exhibits excellent effects in terms of discoloration due to retention in the cylinder, scorching on the screw, mold deposit, etc. due to their synergistic effect. In addition, it also exhibits excellent effects in preventing thermal 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, discoloration due to retention, occurrence of scorching, and occurrence of mold deposit (hereinafter abbreviated as "wedding") according to the following method.

Sample pellet 1 in a cocked syringe with a gas generation volume of 20 ml
．． Insert the aluminum boat carrying Of, insert the cylinder moistened with heat-resistant silicone oil, replace the internal air with nitrogen 15 times, then immerse it in a silicone oil bath at 230℃, and after 20 minutes, change the actual volume. The amount of gas generated S (d/f) is the increase amount (measured volume value - blank test volume value)
shall be.

Pellets 500"W were placed in a test tube with a retention discoloration diameter of 8 m, and
After heating in a silicone oil bath at 0°C for 60 minutes, it was rapidly cooled and expressed by the color rank at that time.

Color rank ◎ White ○ Mu Pale yellowish brown △ × ×× Brown burnt occurrence and MD occurrence Using a 1-ounce injection molding machine, the cylinder temperature was 200°C
In continuous injection molding at a mold temperature of 80° C., it is expressed as 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 starts to lose its luster due to MD occurrence.

Examples 1 to 13, Comparative Examples 1 to 7 n-aminopropyltriethoxysilane (Al, n-aminopropylmethyljethoxysilane (Bl, n-aminopropyldimethylethoxysilane (C1 alone or as a mixture, and OH at both ends) type polydimethylsiloxane (D),
One-end OH type polydimethylsiloxane (Kl alone or as a mixture) was reacted with the temperature raised from 100°C to 200°C over 45 minutes, and the alcohol was completely removed to obtain the polyalkylsiloxane of the present invention.

Next, powdered terminal acetylated polyacetal homopolymer (Ho) or trioxane and ethylene oxide (2
To 100 parts by weight of copolymer (Co) with mol%), various polyalkylsiloxanes obtained above and antioxidant 2 were added.
, 0.25 parts by weight of 2'-methylenebis(4-methyl-6-tert-butylphenol) and heated at 190°C.
It was extruded and pelletized.

After drying this at 80° C. for 14 hours, a thermal stability test was conducted. The results are shown in Table 1.

As is clear from Table 1, the composition containing the polyalkylsiloxane of the present invention has a slightly stronger anti-thermal decomposition property than the composition containing a polyamide resin, but within a range that does not cause any practical problems. It is far superior in terms of reeds, discoloration, scorching on screws, and mold deposits, and can be said to be a well-balanced composition.

Examples 14 to 23 Cyanopropylmethyljethoxysilane (Fl and both terminal OH type polydimethylsiloxane were heated at 60°C in a nitrogen stream.
The reaction was carried out by raising the temperature from 100° C. to 200° C. over a period of minutes, and the alcohol was completely removed to obtain cyanopropyl polydimethylsiloxane. This was blended into a polyacetal resin in the same manner as in the above example, pelletized, and evaluated for thermal stability.

Further, cyanopropylpolydimethylsiloxane synthesized by the above method was mixed with a 30% aqueous solution of caustic soda and 9%
After stirring and reacting at 0°C for 3 hours, neutralization with hydrochloric acid, extraction with ether, washing with water, distillation, and drying were performed to obtain amidopropylpolydimethylsiloxane. This was blended into a polyacetal resin in the same manner as in the above example, pelletized, and evaluated for thermal stability.

These results are shown in Table 2.

＼ As is clear from Table 2, boridimethylchloroxane containing a cyano group and an amide group is also excellent in thermal decomposition prevention properties, retention discoloration, scorching, and mold deposits.

Examples 24 to 27 After reacting n-aminopropyltriethoquinonerane (Al, n-aminobrobylmethyldiethoquinonerane (Bl) alone or as a mixture with water in dioxane at 80°C for 3 hours, the product was produced. The product was precipitated by adding ethyl acetate, filtered, washed and dried to obtain the polyalkylsiloxane of the present invention.

Next, polyacecool homopolymer (Ho)lo.

The polyalkyl/loxane obtained above and the antioxidant 2,2'-methylenebis(4-methyl-6-ter
t-butylphenol) by blending 0.25 parts by weight to 1
It was extruded and pelletized at 90°C. This is 80℃, 14
After drying for an hour, a thermal stability test was conducted.

The results are shown in Table 3.

As is clear from Table 3, the siloxane polymer with an amino group/riion molar ratio of -1A also exhibits thermal decomposition, retention discoloration,
It is found that it improves scorching and mold deposits.

Example 28.29 Polyamide copolymer heat stabilizer (Ny6/Ny66/
Ny610 = 50/30/20) and n-aminopropyltriethoxine run obtained by the method of Examples 1 to 13 (a polyacetal resin composition containing a reaction polymer of Al and one-terminal OH type polydimethylsiloxane). The thermal stability of the product was evaluated.

The results are shown in Table 4.

As is clear from Table 4, the system in which a polyamide thermal stabilizer and the polyargyrunlogisan of the present invention are combined has higher thermal decomposition, retention discoloration, scorching, and mold deformation than the system using only polyamide. It can be seen that the knot is superior in all respects.

Patent applicant Asahi Kasei Shigyo Co., Ltd. Agent Akira Agata q ;q

Claims (1)

[Scope of Claims] 1 100 parts by weight of polyacetal resin, general formula % formula % (in the formula, R1 is a linear or branched alkylene group having 1 to 1 carbon atoms, and R2 is an alkylene group having 1 to 1 carbon atoms) 0.00 Polyalkylsiloxane having at least one functional group represented by
A polyacetal resin composition with improved thermal stability and mold deposit, characterized by containing 5 to 5 parts by weight. 2 Polyacetal resin Zoo weight part, general formula % formula % (In the formula, R1 is a straight chain or branched alkylene group having 1 to 10 carbon atoms, R2 is a straight chain or branched chain having 1 to 10 carbon atoms) polyalkylsiloxane having at least one kind of functional group represented by (alkyl group having a chain) 0.00
A polyacetal resin composition with improved thermal stability and mold deposit, characterized in that it contains 5 to 5 parts by weight of a polyamide resin and 0.01 to 10 parts by weight of a polyamide resin.