JPS62280253A - Acetal resin composition - Google Patents

Abstract

PURPOSE:To provide the title compsn. having excellent mechanical properties and thermal stability as well as good mold release characteristic and giving molded products having excellent appearances, etc., by adding a low-molecular hydrocarbon and a higher fatty acid amide to an acetal resin. CONSTITUTION:100pts.wt. acetal resin (A) is mixed with 0.02-1.00pt.wt. low- molecular hydrocarbon (B) having an MW of 200-1,800 (e.g., petroleum paraffin) and 0.02-1.00pt.wt. 7-24C higher fatty acid amide (C) such as ethylenebisstearamide, stearamide, behenamide, oleamide, etc., in such a proportion as to give 0.04-1.02pts.wt. in total of the components B and C. The mixture is melt-kneaded at 175-230 deg.C.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention provides an acetal resin that does not substantially impair its inherent mechanical properties, thermal stability, or appearance of molded products. The present invention relates to an acetal resin composition that has extremely improved mold release properties during injection molding.

[Conventional technology]

Acetal resin has properties such as well-balanced mechanical properties, excellent friction and wear resistance, and excellent heat resistance, as well as excellent fluidity, so it can be used to create complex structures by injection molding. Often used in mechanical parts and precision mechanical parts, such complex groove structures are used, for example, in thick and thin parts,
Furthermore, it has a shape in which the ultra-thin parts are intertwined with each other, and it is also equipped with hollow cylindrical protrusions, etc., and it weighs several grams.
In many cases, these are small parts with a weight of several logs at most.

For molded products with such complex shapes, the ejection and release of the molded product must be as smooth as possible. If the product is ejected and released with excessive force, the product may be damaged or molded distortion may occur. This has the extremely undesirable effect of being stored inside the product and having an adverse effect that is exposed during long-term use.Therefore, improvement in mold releasability is strongly desired.

[Conventional technology]

Several proposals have been made to improve mold releasability,
For example, Japanese Patent Publication No. 7544/1986 describes the addition of low molecular weight hydrocarbons to acetal resin;
No. 31020 each proposes adding a higher fatty acid amide to an acetal resin.

[Problem that the invention seeks to solve]

However, the mold release effect in these known techniques is
This does not necessarily fully meet market demands, and further improvement in mold release properties has been desired.

Means for Solving Problem C] In view of these drawbacks of the conventional techniques, the present inventors have conducted extensive research and found that when low molecular weight hydrocarbons and higher fatty acid amides, which are ineffective when used alone, are used in combination, significant It was discovered that a synergistic effect is exhibited, and the present invention was achieved.

That is, in the present invention, the acetal resin contains molecules of 9200 to 180.
This is an acetal resin composition formed by adding 0 low molecular weight hydrocarbon and a higher fatty acid amide having 7 to 24 carbon atoms.

The low molecular weight hydrocarbons with a molecular weight of 200 to 1,800 used in the composition of the present invention are usually called petroleum-based paraffins, and the higher fatty acid amides with an industrial accident prime number of 7 to 24 are hydrocarbons with a carbon number of 7 to 24. Among the compounds of higher fatty acids and aliphatic amines, ethylene bisstearamide, stearamide, behenamide and oleic acid amide are particularly preferred.

The amount of the low molecular weight hydrocarbon and higher fatty acid amide added to the acetal resin is 0.02 to 1.00 parts by weight, and the total amount is 0.04 to 1.02 parts by weight per 100 parts by weight of the acetal resin. A range that is appropriate is appropriate. If the amount is less than these lower limits, the effect will be insufficient in practical terms, while if the amount exceeds the upper limit, the inherent properties of the acetal resin, particularly the thermal stability and molded appearance (color tone), will deteriorate.

The acetal resin used in the composition of the present invention is produced from a cyclic oligomer such as formaldehyde monomer or its trimer (trioxane) or tetramer (tetraoxane) and is made essentially of oxymethylene units. oxymethylene homopolymer, and carbon produced from the above raw materials and a cyclic ether such as ethylene oxide, propylene oxide, epichlorohydrin, 1,3-dioxolane, 1,3-dioxolane, glycol formal, diglycol formal, etc. number 2~8
oxymethylene copolymers containing from 0.1 to 20% by weight of oxyalkylene units.

The composition of the present invention may further contain heat stabilizers, antioxidants, ultraviolet absorbers, pigments, fillers, glass fibers, carbon fibers, and other known additives.

Various methods can be used to produce the acetal resin composition of the present invention, but it is essential to melt and knead each component.

As equipment used for melt-kneading, general kneading machines such as various extruders, kneaders, Banbury mixers, and mixing rolls are used. The mixture obtained by tri-blending with a gentle mixing device or a high-speed fluid mixing device such as a Henschel mixer, or by stirring and mixing in the state of a solution, emulsion, suspension, etc., and then drying it is transferred to the above-mentioned kneading machine. A method of adding a low molecular weight hydrocarbon and a higher fatty acid amide to an acetal resin composition in a homogeneous molten state using the above-mentioned kneading machine, A method of adding a low molecular weight hydrocarbon and a higher fatty acid amide to an acetal resin composition in a pellet state, There is a method of directly feeding a triblended mixture to a molding machine.

The melt-kneading temperature is appropriately selected depending on various conditions such as the type of acetal resin used, the function of the mixing and kneading equipment, and the purpose, but it is within the temperature range of above the melting point of the acetal resin and below the decomposition temperature and below the decomposition temperature of various additives. - 175-230'C is suitable for ships.

[Action and effect of invention]

In the composition of the present invention, it is not clear why low molecular weight hydrocarbons and higher fatty acid amides, which show only a weak effect when used alone, have an excellent effect, but compared to the case where each is added alone, they are more effective against acetal resin. It is speculated that this is because the compatibility becomes more appropriate, resulting in the formation of a type of layer that can be easily released from the mold at the interface between the mold cavity surface and the resin.

〔Example〕

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

In the following description, the intrinsic viscosity [η] indicates the value measured at 60°C in p-chlorophenol to which 2% by weight of α-pinene has been added, and the amount added (Cphr) is the value measured at 60°C in p-chlorophenol to which 2% by weight of α-pinene has been added. Parts by weight are shown.

In addition, each test in Table 2 was conducted in the following manner.

Shape of molded product: Height: 27 mm, outer diameter: 341 mm, thickness: 21 mm. Cylindrical shape with a bottom. Release force is sensed by a sensor connected to a protruding pin located at the center of the cylindrical bottom. Sensor for measuring mold release force: @ Techno Plus Molding conditions: Injection molding machine; Toshiba 1s-90B injection pressure; 800k
g/cm" Mold temperature: 60°C Ratio: Ratio of mold release force to the mold release force of Example 1 Color difference meter: Hunter color difference meter (@Suga Test Instruments) Molded product before adding mold release agent Color tone - Ll % al, b1 Color tone of molded product after addition of mold release agent - Ll % 31% b1 calculation formula: % formula % Color difference meter: Hunter color difference meter (@Suga Test Instruments) Injection molding machine: 5J manufactured by Taki Seisakusho -35A retention conditions: material temperature; 23
5°C Residence time; Color tone of molded product before residence for 60 minutes = L1, a□, b3 Color tone of molded product after residence = L 4, a a, b 4 Calculation formula: % formula % Test: 222" C2 in air Thermal decomposition rate W Hisaku team!
(e) Leather test piece molding conditions: Molding machine; SJ-5A manufactured by Taki Seisakusho Material temperature: 200°C Injection pressure: 500 kg/cm2 Mold temperature: 80°C Examples 1 to 9 and Comparative Examples 1 to 2 [ η)-1,4 dl/g, an acetal resin which is an oxymethylene copolymer containing 2.5% by weight of copolymerized units derived from ethylene oxide, 0.2 phr of melamine as thermal oxidative stabilizer, sterically hindered Phenol (Irganonx 1010 manufactured by Ciba Geigy) 0.
An acetal resin composition containing 4 phr of magnesium hydroxide and 0°1 ρhr of magnesium hydroxide, and the types and amounts of low molecular weight hydrocarbons and higher fatty acid amides listed in Table 1 was prepared by adding L/
It was manufactured using a vented twin-screw extruder with D=30 and diameter of 50 mm.

Regarding the obtained samples, the mold release force, molded product appearance (color tone),
Thermal stability and tensile impact strength were measured and the results are shown in Table 2 as Examples 1 to 9.

For comparison, examples and results in which either the low molecular weight hydrocarbon or the higher fatty acid amide was not added are shown in Tables 1 and 2 as Comparative Examples 1 and 2.

Example 10 [η]=1.4d! /g of oxymethylene copolymer containing 2.5% by weight of copolymerized units derived from ethylene oxide, and 0.2% of melamine as a thermal oxidative stabilizer.
Phr, a stabilized acetal resin composition in the form of pellets containing 0.4 phr of sterically hindered phenol (Irganox 1010 manufactured by Ciba Geigy) and 0.1 phr of magnesium hydroxide was prepared using the types listed in Table 1. and amount of low molecular weight hydrocarbon and higher fatty acid amide in a Henschel mixer (Mitsui Miike ■!!) and mixed at high speed, then melt-kneaded using a vented triple screw extruder with L/D = 30 and diameter of 5 Qmm. An acetal resin composition was obtained.

The obtained sample was subjected to the same test as in Example 1, and the results are shown in Table 2 as Example 10.

Example 11 and Comparative Examples 3 to 4 Acetal resin has [η) = 1.44i/g, 1
．． 3.5 copolymerized units derived from 3-dioxepane
Example 11 was carried out in the same manner as in Example 1, except that the oxymethylene copolymer contained % by weight.
It is shown in Table 2 as follows.

For comparison, examples and results in which either the low molecular weight hydrocarbon or the higher fatty acid amide was not added are shown in Tables 1 and 2 as Comparative Examples 3 and 4.

Example 12 and Comparative Examples 5 to 6 Same as Example 1 except that the acetal resin is an oxymethylene homopolymer whose terminal hydroxyl group is acetylated with [η)-1.3 dl/g acetic anhydride. The results are shown in Table 2 as Example 12.

For comparison, examples and results in which either the low molecular weight hydrocarbon or the higher fatty acid amide was not added are shown in Tables 1 and 2 as Comparative Examples 5 and 6.

Claims (2)

[Claims] (1) An acetal resin composition obtained by adding a low molecular weight hydrocarbon having a molecular weight of 200 to 1800 and a higher fatty acid amide having 7 to 24 carbon atoms to an acetal resin. (2) The individual amounts of low molecular weight hydrocarbons and higher fatty acid amides added to 100 parts by weight of acetal resin are all 0.
．． 02 to 1.00 parts by weight, and the total amount added is 0.0
4 to 1.02 parts by weight of the acetal resin composition according to claim (1).