TW201835207A - Polyacetal resin composition and method for producing same - Google Patents

Abstract

The aim of the present invention is to provide a polyacetal resin composition with which the occurrence of clogging in the screen mesh of an extruder can be suppressed. This aim is achieved by a polyacetal resin composition which comprises (A) 100 parts by mass of polyacetal resin, (B) 0.01 to 1.0 parts by mass of a hindered phenolic antioxidant, and (C) 0.01 to 0.5 parts by mass of a fatty acid calcium salt, the amount of Al relative to the (C) fatty acid calcium salt being 50 ppm or less.

Description

 Polyacetal resin composition and method of producing the same  

The invention relates to a polyacetal resin combination which can reduce the resin pressure caused by the clogging of the screen in the discharge part of the extruder when the mixture is heated and kneaded by using the hindered phenolic antioxidant in the polyacetal resin. A polyacetal resin composition which is excellent in color tone, discoloration property, and hot water resistance.

The polyacetal resin has been widely used in automobiles, electric power, electronic equipment, other precision machines, and building materials piping because of its mechanical properties, fatigue resistance, abrasion resistance, abrasion resistance, chemical resistance, and moldability. In order to improve the heat stability and coloring property of the polyacetal resin for the purpose of use, a fatty acid calcium salt is often added (Patent Document 1).

On the other hand, the calcium content and the fatty acid are simultaneously present, and the Na content and the 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 color of the polyacetal resin composition, and although it has a trace amount of an impurity metal, it can provide good physical properties and color.

[Previous Technical Literature]

[Patent Literature]

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

Patent Document 2: International Publication No. 2005/071011

However, in the procedure of resin kneading and extrusion, when the fatty acid calcium salt is repeatedly produced, the resin pressure rises in the upstream portion of the perforated plate in which the screen is placed. When this pressure rises, the temperature of the resin increases, and the quality of the particles after the extrusion is deteriorated is deteriorated.

Further, if the pressure rises too much in a short period of time, problems such as failure of the exhaust gas may occur, and in order to solve the pressure rise caused by the clogging of the screen, the screen mesh must be frequently replaced, resulting in a decrease in productivity. In addition, in the product quality after extrusion, there is a problem that the discoloration property is large and the hot water resistance is insufficient.

An object of the present invention is to provide a polyacetal resin composition which can suppress clogging of a screen and suppress an increase in resin pressure of an extruder discharge portion. Further, the present invention further provides a polyacetal resin composition having good color tone, retention discoloration property, and hot water resistance.

The inventors have found that the object of the present invention can be attained by the following methods.

(1) A polyacetal resin composition comprising: (A) a polyacetal resin of 100 parts by mass; (B) a hindered phenol antioxidant of 0.01 to 1.0 part by mass; and (C) a mass of 0.01 to 0.5 mass% A fatty acid calcium salt in which the (C) fatty acid calcium salt has an aluminum content of 50 ppm or less.

(2) The polyacetal resin composition according to (1), wherein the calcium content of the fatty acid calcium salt is 100 ppm or less.

(3) The polyacetal resin composition according to (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 for producing a polyacetal resin composition comprising introducing a raw material composition containing a polyacetal resin, a hindered phenol antioxidant, and a fatty acid calcium salt into an extruder, and the raw material composition is placed in an extruder The mixture is kneaded and extruded to form a polyacetal resin composition in which the calcium content of the fatty acid calcium salt is 50 ppm or less.

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

<Polyacetal resin composition>

The polyacetal resin composition of the present invention contains (A) a polyacetal resin of 100 parts by mass, (B) a hindered phenol antioxidant of 0.01 to 1.0 mass%, and (C) a fatty acid calcium salt of 0.01 to 0.5 mass%. Further, the calcium 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 impair the object of the present invention, and can be appropriately selected from polyacetal resins used in various applications.

The polyacetal resin includes a polyacetal homopolymer having 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 comprises an oxygen C2-6 olefin unit (for example, an oxyethylene group (-CH ₂ CH ₂ O-), an oxypropylene group, an oxytetramethylene group or the like). The content of the copolymer unit is, for example, from 0.01 to 30 mol%, preferably from 0.03 to 20 mol%, more preferably from 0.03 to 15 mol%, based on the entire constituent unit of the polyacetal resin.

When the polyacetal resin is a polyacetal copolymer, a copolymer composed of two components, a terpolymer composed of three components, and the like are preferable. The polyacetal copolymer is preferably a random copolymer, a block copolymer, a graft copolymer or the like. Further, the polyacetal resin may have not only a linear branch structure but also a bridging structure. Further, the terminal of the polyacetal resin can be stabilized by a carboxylic acid such as acetic acid or propionic acid or an anhydride thereof, and esterification thereof.

The polyacetal resin can be produced, for example, by anionic polymerization of formaldehyde. In addition, trioxane or formaldehyde can be used as the main monomer, and ethylene oxide, propylene oxide, 1,3-dioxolane, 1,3-dioxane, diethylene glycol formal, 1, A cyclic ether such as 4-butanediol formal or a cyclic methylal is used as a copolymer to carry out cationic copolymerization.

Hindered Phenolic Antioxidants

The structure of the hindered phenol antioxidant used in the present invention is not particularly limited, and IRGANOX 1010, the same 1035, the same 1076, the same 1098, the same 1135, the same 1330, the same 1425, the same 245, the same 259, the same 565, the same can be used. A commercially available compound such as 3114 (the above product is manufactured by BASF Japan Co., Ltd.).

The content of the hindered phenol antioxidant in the polyacetal resin composition is 0.01 parts 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 mass part or more and 0.6 mass part or less.

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

Fatty Acid Calcium

The fatty acid formed by the fatty acid calcium salt may be a saturated fatty acid or an unsaturated fatty acid. The fatty acid is a unit having a carbon number of 10 or more or a dibasic fatty acid, for example, a unit saturated fatty acid having 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 acid (preferably C10-30 saturated fatty acid) such as capric acid or montanic acid, and monounsaturated fatty acid having 10 or more carbon atoms, oleic acid, linoleic acid, linolenic acid, arachidonic acid, mustard C10-34 unsaturated fatty acid (preferably C10-30 unsaturated fatty acid) such as acid, and dibasic fatty acid (dibasic fatty acid) having 10 or more carbon atoms "sebacic acid, dodecanoic acid, tetradecane" A C10-30 unsaturated fatty acid such as a C10-30 saturated fatty acid (preferably a binary C10-20 saturated fatty acid), azelaic acid or dodecenedioic acid such as acid or hexadecanedioic acid ( It is preferably a binary C10-20 unsaturated fatty acid).

Further, a part of the fatty acid of the above-mentioned fatty acid may be substituted with a substituent such as a hydroxyl group, and a fatty acid having one or a plurality of hydroxyl groups in the molecule (for example, a hydroxyl-saturated C10-26 fatty acid such as 12-hydroxystearic acid) may be purified. The purity may include fatty acids having different carbon numbers.

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

The content of the fatty acid calcium salt in the polyacetal resin composition is 0.01 part by mass or more and 0.5 part by mass or less in 100 parts by mass of the polyacetal resin. When 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 part 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 part by mass or more and 0.4 part by mass or less.

"Aluminum content of fatty acid calcium salt is 50 ppm or less"

The present inventors have found that by reducing the aluminum (Al) content of the fatty acid calcium salt, the productivity of the screen clogging is suppressed. The Al content may be as small as possible, and if it is 50 ppm or less, the time for exchanging the screen can be greatly delayed, and 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 by recrystallizing and washing the synthesized fatty acid calcium salt with an organic solvent-ion exchange liquid.

At the same time, reducing the sodium (Na) content of other metals can also inhibit the occurrence of screen clogging. A Na content of 100 ppm or less can exert an effect.

<Other ingredients>

The polyacetal resin composition can be blended with various stabilizers or additives known to the extent that the object or effect of the present invention is not impaired. For example, various coloring agents, mold release agents, stabilizers such as melamine, nucleating agents, antistatic agents, other surfactants, heterogeneous polymers, and the like.

<Method for Producing Polyacetal Resin Composition>

The method for producing the polyacetal resin composition is not particularly limited, and a method comprising the above-mentioned blending ratio component can be used. For example, a generally known method which is easy to manufacture can be used as a method of producing the resin composition. Specifically, after mixing the components constituting the composition, the mixture is melt-kneaded by a one-axis or two-axis extruder, and cut, and then a granular composition is produced.

[Examples]

Hereinafter, the invention will be specifically described by way of specific examples, 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 9.0 g/10 min

A continuous two-axis polymerization machine was used as the polymerization reactor. This polymerization machine has a bush for heating or cooling the outside, and has two rotary shafts in the longitudinal direction in which a plurality of blades for stirring and propelling are provided. The heat medium of 80 ° C was passed through the bush of the two-axis polymerization machine, and the two rotary shafts were rotated at a certain speed while one end continuously supplied trioxane containing 650 ppm of methylal as a chain shifting agent, relative to the total polymerization. (trioxane and copolymer), 3.3 mass% of 1,3-dioxane as a copolymer was added, and 20 ppm of boron trifluoride as a starter was continuously added to the mixture to carry out copolymerization.

Thereafter, the crude polyacetal resin copolymer was discharged from the discharge port provided at the other end of the polymerization machine. The discharged reaction product was immediately passed through a crusher, and a starter was deactivated by adding a 0.05% by mass aqueous solution of triethylamine at 60 °C. Next, separation, washing, and drying are carried out to obtain a crude polyacetal resin copolymer.

Next, a 100 mass% crude acetal resin copolymer was added with a 3% by mass of a 5% by mass aqueous solution of triethylamine, and melt-kneaded at 210 ° C with a two-axis extruder to remove unstable portions. Polyacetal resin. Using a melt index measuring apparatus: Melt Indexer L202 type (manufactured by TAKARA THERMISTOR Co., Ltd.), the measurement was carried out under the conditions of a weight of 2.16 kg and a temperature of 190 ° C, and the melt index (MI) was 9.0 g/10 min.

[(B) Hindered Phenolic Antioxidants]

Pentaerythritol tetrakis[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 an Al content of 5 ppm and a Na content of 40 ppm

C-2: 12-hydroxystearic acid calcium with an Al content of 1000 ppm and a Na content of 350 ppm (no Al, Na reduction treatment)

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

C-4: calcium palmitate with an Al content of 900 ppm and a Na content of 400 ppm (no Al, Na reduction treatment)

C-5: calcium stearate having an Al content of 5 ppm and an Na content of 10 ppm

C-6: calcium stearate with an amount of Al of 950 ppm and an amount of Na of 300 ppm (no Al, Na reduction treatment)

C-7: 12-hydroxystearic acid calcium having an Al content of 100 ppm and an Na content of 50 ppm

C-8: calcium 12-hydroxystearate with an Al content of 45 ppm and a Na content of 20 ppm

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

Dry ashing: 0.1 g of sample was obtained from platinum ruthenium, carbonized by an electric furnace, and ashed in an electric furnace (600 ° C × 1 hour). The ashed sample was dissolved in 5 mL of a 3.5% aqueous hydrochloric acid solution, and made up to 25 mL in ultrapure water.

[Manufacture of Polyacetal Resin Composition]

The production of the polyacetal resin composition can be easily carried out by a generally known method. The (A) polyacetal resin, (B) hindered phenol antioxidant, and (C) fatty acid calcium salt are added and mixed in the ratio shown in Table 1, and melt-kneaded by a biaxial extruder to produce the examples and comparative examples. Granular resin composition.

The two-axis extruder has a 30 mm particle opening and a discharge portion of a 100 mesh screen. With L/D=35, the extrusion temperature was 200 ° C, the number of cylinder revolutions was 120 rpm, the exhaust vacuum was 700 mmHg, and the discharge amount was 15 kg/hour.

The polyacetal resin composition produced by the above method was subjected to the following evaluation. The measurement was carried out under the conditions of 23 ° C and 50% RH unless otherwise specified.

<Discoloration degree of melt retention (residual discoloration)>

In the polyacetal resin compositions prepared in the examples and the comparative examples, various 70 mm × 50 mm × 3 mm flat plates were formed under the two molding conditions shown next, and the color tone (L, a, b) of each molded article was The SE-2000 colorimeter (manufactured by Nippon Denshoku Industries Co., Ltd.) was measured. Thereafter, the degree of discoloration (ΔE) after the melt retention was calculated.

(co-forming conditions)

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

Cylinder temperature: 210 ° C (from feed to nozzle)

Mold temperature: 80 ° C

Injection speed: 1.5m/min

(variable molding conditions)

Molding Condition 1: The molten resin in the cylinder was not retained, and molding was carried out in a molding cycle of 40 seconds.

Molding Condition 2: The molten resin in the cylinder was retained for 30 minutes, and then molded.

(Calculation of discoloration (ΔE) after discoloration and discoloration)

The degree of discoloration (ΔE) after discoloration of the melt retention 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 tone of the molded article of the molding condition 2 (after staying for 30 minutes), and L ₀ , a ₀ , and b ₀ are the color tone of the molded article of the molding condition 1.

<The evaluation of hot water resistance>

A tensile test piece was used according to ISO 20753 (Type 1A), and it was immersed in an autoclave containing hot water of 120 ° C for 10 days, and then taken out, and subjected to a tensile test in accordance with ISO 527-1, 2. The tensile strength retention ratio was measured in accordance with the above criteria, and the tensile strength before immersion was set to 100%.

<Evaluation of particle tone>

Using a colorimeter SE-2000 (manufactured by Nippon Denshoku Industries Co., Ltd.), a certain amount of particles was added to a measuring tube (particle tube) for granules, placed on a detection table, and a lid was placed to read the b value.

<rise of resin pressure>

After starting the extrusion for 4 hours, compared with the initial pressure, the pressure rise is less than 5% and is indicated as ◎, 5% or more and less than 10% is indicated as ○, and 10% or more is indicated as ×.

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

It can be confirmed from Tables 1 and 2 that the resin pressure can be suppressed and the productivity can be improved by reducing the amount of Al. At the same time, the color tone, retention discoloration and hot water resistance of the particles can also be improved.

Claims (4)

 A polyacetal resin composition comprising: (A) a 100-mass polyacetal resin; (B) a 0.01 to 1.0 mass portion of a hindered phenol antioxidant; and (C) a 0.01 to 0.5 mass portion A fatty acid calcium salt in which the (C) fatty acid calcium salt has an aluminum content of 50 ppm or less.    The polyacetal resin composition according to claim 1, wherein the fatty acid calcium salt has a sodium content of 100 ppm or less.    The polyacetal resin composition according to claim 1 or 2, 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 of the groups.    A method for producing a polyacetal resin composition comprising: feeding a raw material composition containing a polyacetal resin, a hindered phenol antioxidant, and a fatty acid calcium salt to an extruder, and mixing the raw material composition in the extruder The polyacetal resin composition is formed by extrusion and extrusion, wherein the calcium salt of the fatty acid has an aluminum content of 50 ppm or less.