TWI749096B - Polyacetal resin composition and manufacturing method thereof - Google Patents

Abstract

The present invention provides a polyacetal resin composition capable of suppressing clogging of the screen of an extruder.

The polyacetal resin composition contains (A) 100 parts by mass of polyacetal resin, (B) 0.01 to 1.0 parts by mass of hindered phenolic antioxidant, and (C) 0.01 to 0.5 parts by mass of fatty acid calcium salt, in which fatty acid The aluminum content of the calcium salt is 50 ppm or less, and the invention can be achieved by the polyacetal resin composition.

Description

Polyacetal resin composition and manufacturing method thereof

The present invention relates to a polyacetal resin combination that utilizes hindered phenolic antioxidants in polyacetal resins and specific fatty acid calcium salts, which can reduce the increase in resin pressure caused by the clogging of the screen of the extruder at the time of heating, kneading and extrusion. It is a polyacetal resin composition with excellent color tone, retention and discoloration, and hot water resistance.

Since polyacetal resin has good mechanical properties, fatigue resistance, abrasion resistance, abrasion resistance, chemical resistance, and moldability, it has been widely used in cars, electric power and electronic equipment, other precision machines, and building piping. In order to improve the heat stability and colorability of polyacetal resins for these purposes, fatty acid calcium salts are often added (Patent Document 1).

On the other hand, calcium carbonate and fatty acids are co-existed, and the Na content and Sr content in the resin composition are adjusted within a predetermined range to improve physical properties such as creep resistance (Patent Document 2).

The fatty acid calcium salt can greatly improve the physical properties and coloring of the polyacetal resin composition. Although it has a small amount of impurity metal, it can provide good physical properties and coloring.

【Prior Technical Literature】

【Patent Literature】

Patent Document 1: Japanese Patent Application Laid-Open No. 2-166149

Patent Document 2: International Publication No. 2005/071011

However, in the process of resin mixing and extrusion, the use of fatty acid calcium salt for repeated production will cause the resin pressure to rise in the upstream part of the perforated plate equipped with the screen. This increase in pressure will increase the temperature of the resin and promote poor quality such as the deterioration of the color of the pellets after extrusion.

In addition, if the pressure rises too much in a short period of time, it will cause problems such as exhaust failure. In order to solve the pressure rise caused by the clogging of the screen, the screen must be replaced frequently, resulting in a decrease in productivity. In addition, in the quality of the product after extrusion, there will be problems of large retention and discoloration and insufficient hot water resistance.

The object of the present invention is to provide a polyacetal resin composition capable of suppressing clogging of the screen and suppressing the increase in the resin pressure of the discharge part of an extruder. In addition, the present invention also provides a polyacetal resin composition with good color tone, retention and discoloration, and hot water resistance.

The inventors found that the purpose of the invention can be achieved by the following methods.

(1) A polyacetal resin composition comprising: (A) 100 parts by mass polyacetal resin; (B) 0.01 to 1.0 parts by mass hindered phenolic antioxidant; and (C) 0.01 to 0.5 parts by mass Fatty acid calcium salt, wherein (C) the aluminum content of the fatty acid calcium salt is 50 ppm or less.

(2) The polyacetal resin composition as described in (1), wherein the sodium content of the fatty acid calcium salt is 100 ppm or less.

(3) The polyacetal resin composition as described in (1) or (2), wherein the (C) fatty acid calcium salt is selected from at least one of calcium 12-hydroxystearate, calcium stearate, and calcium palmitate.

(4) A method of manufacturing a polyacetal resin composition, including adding a raw material composition containing polyacetal resin, hindered phenolic antioxidants and fatty acid calcium salt into an extruder, and the raw material composition in the extruder It is kneaded and extruded to form a polyacetal resin composition, wherein the aluminum content of the fatty acid calcium salt is 50 ppm or less.

Hereinafter, the implementation of the present invention will be described in detail.

<Polyacetal resin composition>

The polyacetal resin composition of the present invention contains (A) 100 parts by mass of polyacetal resin, (B) 0.01 to 1.0 parts by mass of hindered phenolic antioxidant, and (C) 0.01 to 0.5 parts by mass of fatty acid calcium salt, And the aluminum content of the fatty acid calcium salt is 50 ppm or less.

"Polyacetal resin"

The polyacetal resin used in the present invention is not particularly limited as long as it does not interfere with the purpose of the present invention, and can be appropriately selected from polyacetal resins used in various applications.

The polyacetal resin includes a polyacetal homopolymer containing only a methoxy group (-CH ₂ O-) as a constituent unit, and a polyacetal copolymer containing a copolymer other than a methoxy group as a constituent unit. In the copolymer, the copolymer unit contains an oxy C2-6 olefin unit (for example, an oxyethylene group (-CH ₂ CH ₂ O-)), an oxypropylene group, an oxytetramethylene group, and other oxy C2-4 olefin units. The content of the copolymer unit is, for example, selected from the range of 0.01 to 30 mol%, preferably 0.03 to 20 mol%, and more preferably 0.03 to 15 mol% with respect to the entire constituent units of the polyacetal resin.

When the polyacetal resin is a polyacetal copolymer, it is preferably a two-component copolymer, a three-component terpolymer or the like. The polyacetal copolymer is preferably a random copolymer, a block copolymer, a graft copolymer, or the like. In addition, the polyacetal resin may not only have a linear branch structure but also a bridging structure. In addition, the ends of the polyacetal resin can be stabilized by, for example, carboxylic acids such as acetic acid and propionic acid or their anhydrates and their esterification.

The polyacetal resin can be produced, for example, by anionic polymerization of formaldehyde. In addition, trioxane or formaldehyde can also be used as the main monomer, with ethylene oxide, propylene oxide, 1,3-dioxolane, 1,3-dioxane, diethylene glycol formal, 1, Cyclic ethers such as 4-butanediol formal or cyclic methylal are copolymers and are produced by cationic copolymerization.

"Hindered Phenolic Antioxidant"

The hindered phenol antioxidant used in the present invention has no special restrictions on its structure. IRGANOX 1010, same 1035, same 1076, same 1098, same 1135, same 1330, same 1425, same 245, same 259, same 565, same 3114, etc. (the above products are made by BASF Japan) and other commercially available compounds.

The content of the hindered phenol antioxidant in the polyacetal resin composition is 0.01 part by mass or more and 1.0 part by mass or less in 100 parts by mass of the polyacetal resin. More preferably, it is 0.1 parts by mass or more and 0.6 parts by mass or less.

If the blending amount of antioxidant is small, sufficient oxidation resistance cannot be obtained, and the effect is not good. (B) When the blending amount of the antioxidant is too large, the mechanical properties and moldability of the resin composition will deteriorate.

"Fatty Acid Calcium"

The fatty acid formed by the fatty acid calcium salt may be a saturated fatty acid or an unsaturated fatty acid. This fatty acid is a unit or dibasic fatty acid with a carbon number of 10 or more. For example, a unit saturated fatty acid with a carbon number of 10 or more "capric acid, lauric acid, myristic acid, pentadecanoic acid, palmitic acid, stearic acid, arachidic acid, mountain C10-34 saturated fatty acids (preferably C10-30 saturated fatty acids) such as linic acid and montanic acid, etc.", unit unsaturated fatty acids with a carbon number of 10 or more "oleic acid, linoleic acid, linolenic acid, arachidonic acid, mustard C10-34 unsaturated fatty acids such as acids (preferably C10-30 unsaturated fatty acids), etc.", dibasic fatty acids (dibasic fatty acids) with a carbon number of 10 or more, "sebacic acid, dodecanoic acid, tetradecane Dibasic C10-30 saturated fatty acids such as acid and hexadecanedioic acid (preferably dibasic C10-20 saturated fatty acids), dibasic C10-30 unsaturated fatty acids such as sebacic acid and dodecenedioic acid ( Preferably, it is a binary C10-20 unsaturated fatty acid), etc.".

In addition, some of the hydrogen atoms of the above fatty acids can be substituted with substituents such as hydroxyl groups, and fatty acids with one or more hydroxyl groups in the molecule (for example, hydroxyl saturated C10-26 fatty acids such as 12-hydroxystearic acid, etc.), depending on purification The purity can include fatty acids with different carbon numbers.

The fatty acid calcium salt of the present invention is preferably calcium stearate, calcium 12-hydroxystearate, or calcium palmitate.

The fatty acid calcium salt content in the polyacetal resin composition is 0.01 parts by mass or more and 0.5 parts by mass or less in 100 parts by mass of the polyacetal resin. If the content of the fatty acid calcium salt is 0.01 parts by mass or more, the heat resistance of the molded body can be improved, and if it is 0.5 parts by mass or less, the discoloration of the molded body can be reduced. The content of the fatty acid calcium salt is preferably 0.03 parts by mass or more and 0.4 parts by mass or less.

"The aluminum content of fatty acid calcium salt is below 50ppm"

The present invention found that the aluminum (Al) content of the fatty acid calcium salt can be reduced to suppress the low productivity caused by the clogging of the screen. The content of Al can be as small as possible. If it is 50 ppm or less, the time for screen exchange can be greatly delayed, and it is more preferably 20 ppm or less.

The Al content in the fatty acid calcium salt can be reduced by reducing the contact with excess metal in the synthesis reaction system, or the synthetic fatty acid calcium salt is recrystallized and washed with an organic solvent-ion exchange liquid.

At the same time, reducing the content of other metal sodium (Na) can also prevent the occurrence of clogging of the screen. The Na content is effective if it is below 100 ppm.

<Other ingredients>

The polyacetal resin composition can be compounded with various known stabilizers or additives within a range that does not affect the purpose or effects of the present invention. For example, various coloring agents, mold release agents, stabilizers such as melamine, nucleating agents, antistatic agents, other surfactants, heterogeneous polymers, etc.

<Production method of polyacetal resin composition>

The production method of the polyacetal resin composition is not particularly limited, and a method containing components in the above-mentioned mixing ratio can be used. For example, a generally known method that can be easily manufactured can be used as a method of manufacturing the resin composition. Specifically, after mixing each component constituting the composition, it is melt-kneaded and extruded with a uniaxial or biaxial extruder, and after cutting, a granular composition is produced.

[Examples]

Hereinafter, the examples are described in detail, and the present invention is specifically described, but it is not limited to the following examples.

<Manufacture of test body>

[(A) Preparation of polyacetal resin]

Polyacetal resin with Al melt index (MI) of 9.0g/10 minutes

A continuous biaxial polymerizer was used as the polymerization reaction device. This polymerizer has a heating or cooling medium bushing on the outside, and two rotating shafts for stirring and propelling a plurality of paddles are installed in the longitudinal direction. The heat medium of 80℃ is passed through the bushing of the two-axis polymerization machine. While the two rotating shafts rotate at a certain speed, one end of the two rotating shafts continuously supplies trioxane containing 650ppm methylal as a chain transfer agent, relative to the total polymerization Compound (trioxane and copolymer), add 3.3% by mass as a copolymer of 1,3-dioxopentane, and continuously add 20 ppm of boron trifluoride as an initiator to this mixed solution for copolymerization.

After that, the crude polyacetal resin copolymer was discharged from a discharge port provided at the other end of the polymerizer. The discharged reaction product immediately passed through the crusher, and an aqueous solution of triethylamine containing 0.05% by mass at 60°C was added to deactivate the initiator. Then, separation, washing, and drying are performed to obtain a crude polyacetal resin copolymer.

Next, for 100 parts by mass of the crude polyacetal resin copolymer, 3% by mass of a 5% by mass triethylamine aqueous solution was added, and the two-axis extruder was used for melt-kneading at 210°C to remove unstable parts. Polyacetal resin. A melt index measuring device: Melt Indexer L202 type (manufactured by TAKARA THERMISTOR) was used for measurement under conditions of a load of 2.16 kg and a temperature of 190°C, and the melt index (MI) was 9.0 g/10 minutes.

[(B) Hindered Phenolic Antioxidant]

Pentaerythritol tetra[3-(3,5-di-t-butyl-4-hydroxy)propionic acid] (trade name: IRGANOX 1010, manufactured by BASF Japan).

[(C) Fatty Acid Calcium Salt]

C-1: Calcium 12-hydroxystearate with 5ppm Al and 40ppm Na

C-2: Calcium 12-hydroxystearate with 1000ppm of Al and 350ppm of Na (no Al and Na reduction treatment)

C-3: Calcium palmitate with 5ppm Al and 20ppm Na

C-4: Calcium palmitate with 900ppm of Al and 400ppm of Na (no Al and Na reduction treatment)

C-5: Calcium stearate with 5ppm Al and 10ppm Na

C-6: Calcium stearate with Al content of 950ppm and Na content of 300ppm (no Al and Na reduction treatment)

C-7: Calcium 12-hydroxystearate with 100ppm Al and 50ppm Na

C-8: Calcium 12-hydroxystearate with 45ppm Al and 20ppm Na

For the Al and Na content of calcium 12-hydroxystearate, calcium palmitate, and calcium stearate, the dry ashing solution can be analyzed by inductively coupled plasma mass spectrometer (ICP-AES, CIROSCCD-120 manufactured by SPECTRO) to Quantify.

Dry ashing: A 0.1g sample is obtained from a platinum crucible, carbonized in an electronic furnace, and then ashed in an electronic furnace (600℃×1 hour). Dissolve the ashed sample in 5 mL of 3.5% hydrochloric acid aqueous solution for recovery, and dilute to 25 mL with ultrapure water.

[Production of polyacetal resin composition]

The production of the polyacetal resin composition can be easily produced using a generally known method. The above (A) polyacetal resin, (B) hindered phenolic antioxidant, and (C) fatty acid calcium salt were added and mixed in the proportions shown in Table 1, and then melted and kneaded by a two-axis extruder to produce examples and comparative examples The granular resin composition.

The two-axis extruder has a 30mm particle port and a discharge section equipped with a 100-mesh screen. Extrusion is performed under the conditions of L/D=35, extrusion temperature of 200°C, cylinder revolutions of 120rpm, exhaust vacuum degree of 700mmHg, and discharge volume of 15kg/hour.

The polyacetal resin composition manufactured by the above-mentioned method was evaluated as follows. If there is no special description in the following evaluation, it is measured under the conditions of 23°C and 50%RH.

<Discoloration degree of melt retention (residence discoloration)>

The polyacetal resin compositions prepared in the Examples and Comparative Examples were formed into various 70mm×50mm×3mm flat plates under the following two molding conditions, and the color tone (L, a, b) of each molded product was SE-2000 colorimeter (manufactured by Nippon Denshoku Industries Co., Ltd.) was used for the measurement. After that, the degree of discoloration (ΔE) after melt retention was calculated.

(Common molding conditions)

Injection molding machine: manufactured by Sumitomo Heavy Industries Co., Ltd. [SE100DU]

Cylinder temperature: 210°C (from feeding part to nozzle)

Mold temperature: 80℃

Injection speed: 1.5m/min

(Variable molding conditions)

Molding condition 1: The molten resin in the cylinder is not retained, and molding is performed in a molding cycle of 40 seconds.

Molding condition 2: After the molten resin in the cylinder stays for 30 minutes, molding is performed.

(Calculation of the degree of discoloration (△E) after melt retention and discoloration)

The degree of discoloration (△E) after melt retention discoloration is calculated by the following equation.

△E={(L ₁ -L ₀ ) ² +(a ₁ -a ₀ ) ² +(b ₁ -b ₀ ) ² } ^1/2

In the present invention, L ₁ , a ₁ , and b ₁ are the color of the molded product under molding condition 2 (after 30 minutes of residence), and L ₀ , a ₀ , and b ₀ are the color of the molded product under molding condition 1.

<Evaluation of hot water resistance>

The tensile test piece was used in accordance with ISO20753 (Type 1A) standards, placed in an autoclave containing hot water at 120°C for 10 days, and then taken out. The tensile test was performed in accordance with ISO527-1,2 standards. The retention of tensile strength was measured in accordance with the above-mentioned reference, and the tensile strength before immersion was set to 100%.

<Evaluation of Grain Tone>

Using a colorimeter SE-2000 (manufactured by Nippon Denshoku Kogyo Co., Ltd.), add a certain amount of particles to a particle measuring tube (particle tube), place it on the detection table, close the lid, and read the b value.

<Rise in resin pressure>

4 hours after the start of extrusion, compared with the initial pressure, a pressure rise of less than 5% is marked as ◎, a pressure increase of 5% or more and less than 10% is marked as ○, and 10% or more is marked as ×.

The results of each formulation are shown in Tables 1 and 2.

From Tables 1 and 2, it can be confirmed that reducing the amount of Al can suppress resin pressure and improve productivity. At the same time, it can also improve the color tone, retention and discoloration and hot water resistance of the particles.

Claims (4)

A polyacetal resin composition comprising: (A)-100 parts by mass of polyacetal resin; (B)-0.01 to 1.0 parts by mass of hindered phenolic antioxidant; and (C)-0.01 to 0.5 parts by mass Fatty acid calcium salt, wherein the aluminum content of the (C) fatty acid calcium salt is greater than 0 ppm and less than 50 ppm. The polyacetal resin composition described in item 1 of the scope of patent application, wherein the sodium content of the fatty acid calcium salt is 100 ppm or less. The polyacetal resin composition described in item 1 or 2 of the scope of patent application, wherein the (C) fatty acid calcium salt is selected from the group consisting of calcium 12-hydroxystearate, calcium stearate, and calcium palmitate At least one in the group. A method for manufacturing a polyacetal resin composition includes feeding a raw material composition containing polyacetal resin, hindered phenolic antioxidants, and fatty acid calcium salt into an extruder, and mixing the raw material composition in the extruder Refining and extruding to form the polyacetal resin composition, wherein the aluminum content of the fatty acid calcium salt is greater than 0 ppm and less than 50 ppm.