JP5632809B2 - Polyacetal resin composition and molded article obtained using the same - Google Patents

Description

  The present invention relates to a polyacetal resin composition and a molded article obtained using the same.

  The engineering plastics polyacetal resin has excellent mechanical properties, sliding properties, friction / abrasion properties, heat resistance, molding processability, and the like, and is often used as a basic component for automobiles, OA equipment and the like. On the other hand, thermoplastic polyurethane has good compatibility with the polyacetal resin, and can impart impact resistance to the polyacetal resin. For this reason, compositions containing a polyacetal resin and a thermoplastic polyurethane are often used.

  As such a composition, what is disclosed by the following patent document 1 is known. In the following Patent Document 1, 40 to 99 parts by weight of a polyoxymethylene resin and 1 to 60 parts by weight of a thermoplastic polyurethane resin with respect to 100 parts by weight of a polyoxymethylene resin and a thermoplastic polyurethane resin, and a polyoxymethylene resin and a thermoplastic resin are disclosed. Containing 0.01 to 5 parts by weight of a maleic anhydride-containing compound with respect to 100 parts by weight of the polyurethane resin, containing 0.05 to 1% by weight of active isocyanate in the thermoplastic polyurethane resin, A composition having a moisture content of 1000 ppm or less is disclosed.

Japanese Patent No. 4183622

  However, the composition described in Patent Document 1 has room for improvement in terms of suppression of the amount of formaldehyde generated and sufficient impact resistance.

  An object of this invention is to provide the polyacetal resin composition which has the outstanding impact resistance, and can fully suppress generation | occurrence | production of formaldehyde, and a molded article obtained using the same.

  As a result of intensive studies to solve the above problems, the present inventors have found that it is effective for improving the impact resistance to make the melt viscosity of the thermoplastic polyurethane a predetermined value or more. As a result of further earnest studies, the present inventors have found that the above-described problems can be solved by the following invention.

  That is, the present invention blends 1 to 120 parts by mass of a thermoplastic polyurethane (B) and 0.01 to 5 parts by mass of a formaldehyde scavenger (C) having formaldehyde-reactive nitrogen with respect to 100 parts by mass of the polyacetal resin (A). And the thermoplastic polyurethane contains a residual isocyanate amount of 0.10% by mass or less, has a moisture content of 3000 ppm by mass or less, and exhibits a melt viscosity of 200,000 poise or more at 180 ° C. It is.

  According to this polyacetal resin composition, it has excellent impact resistance and can sufficiently suppress generation of formaldehyde.

  Here, the present inventors presume the reason why the impact resistance can be improved and the generation of formaldehyde can be sufficiently suppressed by setting the melt viscosity of the thermoplastic polyurethane within the above range.

  That is, when the melt viscosity is less than 200,000 poise, the impact resistance of the polyacetal resin composition becomes insufficient, and it becomes difficult to obtain a polyacetal resin composition excellent in impact resistance, which is an object of the present invention. Further, in order to obtain impact resistance using a thermoplastic polyurethane having insufficient melt viscosity, an excessive amount of thermoplastic polyurethane is required. However, this impairs the inherent rigidity of polyacetal, and at the same time, another object of the present invention. It will inhibit the formaldehyde generation suppression effect.

  Moreover, this invention is a molded article formed by shape | molding the polyacetal resin composition mentioned above.

  ADVANTAGE OF THE INVENTION According to this invention, it has the outstanding impact resistance and the polyacetal resin composition which can fully suppress generation | occurrence | production of formaldehyde, and a molded article obtained by using the same are provided.

  Hereinafter, the present invention will be described in detail.

  In the present invention, 100 parts by mass of the polyacetal resin (A) is blended with 1 to 120 parts by mass of a thermoplastic polyurethane (B) and 0.01 to 5 parts by mass of a formaldehyde scavenger (C) having formaldehyde-reactive nitrogen. The thermoplastic polyurethane is a polyacetal resin composition containing a residual isocyanate amount of 0.10% by mass or less, having a moisture content of 3000 ppm by mass or less, and having a melt viscosity of 200,000 poise or more at 180 ° C. .

(A) Polyacetal resin A polyacetal resin has a divalent oxymethylene group as a structural unit. The polyacetal resin used in the present invention includes, in addition to the acetal homopolymer consisting of only this structural unit, a copolymer (block copolymer) or terpolymer containing one or more repeating structural units other than oxymethylene groups, and a linear structure. Not only that, it may have a branched or crosslinked structure.

  In order to produce the polyacetal resin, a main raw material containing trioxane is usually used. The main raw material is composed only of trioxane when producing the acetal homopolymer. When the copolymer or terpolymer is produced, the main raw material includes a comonomer in addition to trioxane.

  Examples of comonomers used for the production of copolymers and terpolymers include cyclic formal and ether. Specific examples include 1,3-dioxolane, 2-ethyl-1,3-dioxolane, 2-propyl-1,3-dioxolane, 2-butyl-1,3-dioxolane, 2,2-dimethyl-1,3. -Dioxolane, 2-phenyl-2-methyl-1,3-dioxolane, 4-methyl-1,3-dioxolane, 2,4-dimethyl-1,3-dioxolane, 2-ethyl-4-methyl-1,3 -Dioxolane, 4,4-dimethyl-1,3-dioxolane, 4,5-dimethyl-1,3-dioxolane, 2,2,4-trimethyl-1,3-dioxolane, 4-hydroxymethyl-1,3- Dioxolane, 4-butyloxymethyl-1,3-dioxolane, 4-phenoxymethyl-1,3-dioxolane, 4-chloromethyl-1,3-dioxolane, 1,3-dioxica Cyclo [3,4.0] nonane, ethylene oxide, propylene oxide, Petit alkylene oxide, epichlorohydrin, styrene oxide, Okishitan, 3,3-bis (chloromethyl) oxetane, tetrahydrofuran, and oxepane, and the like. Of these, 1,3-dioxolane is particularly preferred.

  It is preferable that the addition amount of a comonomer is 0.2-30 mass parts with respect to 100 mass parts of trioxane, More preferably, it is 0.5-20 mass parts. When the addition amount of the comonomer is more than 30 parts by mass, the polymerization yield decreases, and when it is less than 0.2 part by mass, the thermal stability decreases.

(B) Thermoplastic polyurethane As the thermoplastic polyurethane, polyurethane having thermoplasticity is used. Polyurethane can be obtained by reacting a diol with a diisocyanate.

  Examples of the diol include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, and the like.

  Examples of the diisocyanate include aromatic diisocyanate, aliphatic diisocyanate, and alicyclic diisocyanate. These can be used alone or in combination of two or more.

  Examples of the aromatic diisocyanate include 1,4-phenylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2-methylene diphenylene diisocyanate, and naphthalene diisocyanate.

  Examples of the aliphatic diisocyanate include hexamethylene diisocyanate.

  Examples of the alicyclic diisocyanate include isophorone diisocyanate, 4,4′-methylene-bis- (cyclohexyl isocyanate), 1,3-bis- (isocyanate methyl) cyclohexane, 1,4-bis- (isocyanate methyl) cyclohexane, and the like. Can be mentioned.

  Diisocyanates are dimers and trimers of the above aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates (hereinafter sometimes referred to as “isocyanate compounds”), carbodiimide modified products of these isocyanate compounds, It may be a prepolymer with a monohydric alcohol, or a blocked isocyanate compound obtained by blocking these isocyanate compounds with a blocking agent such as phenol, primary alcohol, or caprolactam.

  The compounding quantity of thermoplastic polyurethane (B) with respect to 100 mass parts of polyacetal resin (A) is 1-120 mass parts. When the blending amount of the thermoplastic polyurethane (B) is less than 1 part by mass, the impact resistance becomes insufficient. On the other hand, if the amount of the thermoplastic polyurethane (B) exceeds 120 parts by mass, the generation of formaldehyde cannot be sufficiently suppressed. In addition, the inherent rigidity of the polyacetal resin is significantly impaired.

  The blending amount of the thermoplastic polyurethane (B) with respect to 100 parts by mass of the polyacetal resin (A) is within a range that does not impair the original rigidity of the polyacetal resin, because it provides sufficient impact resistance to the polyacetal resin composition. Preferably they are 10 mass parts-120 mass parts, More preferably, they are 33 mass parts-110 mass parts.

  In the thermoplastic polyurethane, diisocyanate that did not contribute to the reaction may remain. Since this residual diisocyanate reacts with the formaldehyde scavenger and reduces the effect of suppressing the generation of formaldehyde, it is preferably as small as possible. Specifically, the amount of the remaining diisocyanate is 0.10% by mass or less based on the thermoplastic polyurethane (100% by mass). When the amount of residual isocyanate exceeds 0.10% by mass, generation of formaldehyde cannot be sufficiently suppressed. The amount of residual isocyanate is preferably 0.05% by mass or less.

  In order to reduce the residual isocyanate amount to 0.10% by mass or less, for example, a method of adjusting the drying conditions after the production of the thermoplastic polyurethane resin and allowing the reaction of unreacted isocyanate groups remaining in the resin to proceed can be mentioned. .

  The water content in the thermoplastic polyurethane is 3000 mass ppm or less. If the water content in the thermoplastic polyurethane exceeds 3000 ppm by mass, the generation of formaldehyde cannot be sufficiently suppressed.

  The water content in the thermoplastic polyurethane is preferably 1500 ppm by mass or less.

  The moisture content in the thermoplastic polyurethane can be reduced by removing moisture in the pellets using a dehumidifying dryer, and can be increased by absorbing the pellets in a humidity-controlled environment.

  The melt viscosity at 180 ° C. of the thermoplastic polyurethane is 200,000 poise or more. When the melt viscosity is less than 200,000 poise, the impact resistance is significantly lowered.

The melt viscosity at 180 ° C. of the thermoplastic polyurethane is preferably 250,000 poise or more. However, the melt viscosity at 180 ° C. of the thermoplastic polyurethane is preferably 600,000 poise or less. In this case, the dispersibility with the polyacetal resin can be further improved as compared with the case where the melt viscosity of the thermoplastic polyurethane at 180 ° C. exceeds 600,000 poise.
In addition, in the polyacetal resin composition of this invention, it is preferable that a maleic anhydride containing compound is not contained. That is, the blending amount of the maleic anhydride-containing compound / (the blending amount of the polyacetal resin (A) + the blending amount of the thermoplastic polyurethane) is preferably 0. In this case, since maleic anhydride is not contained, decomposition of the polyacetal resin can be more sufficiently suppressed, and the formaldehyde generation suppression effect which is the object of the present invention can be more easily realized.

(C) Formaldehyde scavenger Any formaldehyde scavenger may be used as long as it can react with formaldehyde and suppress the release of formaldehyde to the outside of the polyacetal resin composition. Specifically, a material having formaldehyde-reactive nitrogen is used as the formaldehyde scavenger. Examples of such materials include those containing nitrogen atoms having formaldehyde reactivity such as dodecanedioic acid dihydrazide, stearic acid hydrazide, and benzoguanamine.

  The compounding quantity of the formaldehyde scavenger with respect to 100 mass parts of polyacetal resin (A) is 0.01-5 mass parts. If the compounding amount of the formaldehyde scavenger is less than 0.01 parts by mass, formaldehyde cannot be sufficiently suppressed. On the other hand, when the compounding quantity of a formaldehyde scavenger exceeds 5 mass parts, impact resistance will fall.

  The blending amount of the formaldehyde scavenger with respect to 100 parts by mass of the polyacetal resin (A) is preferably 0.02 to 2 parts by mass.

  The polyacetal resin composition includes a known antioxidant (for example, triethylene glycol-bis [3 (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate]), a heat stabilizer (for example, melamine) One or more additives can be added.

  Further, one or more known release agents (polyethylene wax, or release agents such as fatty acid ester-based or silicon-based compounds such as pentaerythritol tetrastearate) may be added to the polyacetal resin composition. it can.

  Furthermore, coloring agents, nucleating agents, plasticizers, fluorescent brighteners, sliding agents, antistatic agents such as polyethylene glycol and glycerin, higher fatty acid salts, UV absorbers such as benzotriazole-based or benzophenone-based compounds, Alternatively, additives such as light stabilizers such as hindered amines can be added as desired.

  Moreover, this invention is a molded article formed by shape | molding the polyacetal resin composition mentioned above.

  The molding method is not particularly limited, and an injection molding method, an extrusion molding method, or the like is used as the molding method.

  As molded products, for example, the generation of formaldehyde during the molding process is suppressed, so as a countermeasure against so-called sick house syndrome, automotive interior parts, interior parts such as houses (hot water mixing taps, etc.), clothing parts (fasteners, belts) Buckles, etc.), building material applications (piping, pump parts, etc.), machine parts (gears, etc.), and the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to the following Example.

Example 1
100 parts by mass of polyacetal resin (A), 33 parts by mass of thermoplastic polyurethane (B) having the physical properties shown in Table 1, and 0.04 parts by mass of formaldehyde scavenger (C) consisting of dodecanedioic acid dihydrazide, manufactured by Kawada Manufacturing Co., Ltd. After mixing uniformly using a supermixer, it is melted under the conditions of a screw rotation speed of 120 rpm and a cylinder set temperature of 190 ° C. using a twin-screw extruder (PCM-30 manufactured by Ikekai Tekko Co., Ltd., screw diameter 30 mm) according to a conventional method After kneading, the pellets were extruded into strands and cut with a pelletizer to produce polyacetal resin composition pellets.

  At this time, the trade name “Iupital F20” (manufactured by Mitsubishi Engineering Plastics) was used as the polyacetal resin (A). The melt index (ASTM-D1238 standard: 190 ° C., 2.16 kg) of this polyacetal resin was 10.5 g / 10 min, and the water content was 400 mass ppm.

  At this time, a thermoplastic polyurethane obtained by reacting adipic acid, 1,4-butanediol and 4,4'-diphenylmethane diisocyanate was used as the thermoplastic polyurethane (B).

Further, the water content of the thermoplastic polyurethane and the polyacetal resin, the melt viscosity of the thermoplastic polyurethane, and the residual isocyanate (NCO) amount of the thermoplastic polyurethane were measured as follows.
(1) Moisture content in thermoplastic polyurethane and polyacetal resin The moisture content in thermoplastic polyurethane and polyacetal resin is based on the Karl Fischer method (ISO15112 / A method) using a moisture measuring device CA-100 manufactured by Mitsubishi Chemical Corporation. And measured.
(2) Melt viscosity of thermoplastic polyurethane The melt viscosity of thermoplastic polyurethane was measured at a measurement temperature of 180 ° C. and a load of 294 N using a measuring instrument of a high and low flow tester CFT500C type (manufactured by Shimadzu Corporation).
(3) Residual isocyanate (NCO) amount in thermoplastic polyurethane For the residual isocyanate (NCO) amount in thermoplastic polyurethane, JIS K 1603-1 (Testing method for polyurethane raw material aromatic isocyanate-isocyanate group content) Was measured according to the method described in 1.

(Examples 2-9 and Comparative Examples 1-9)
Blending amount of thermoplastic polyurethane (B), blending amount of formaldehyde scavenger (C), moisture content in thermoplastic polyurethane, residual isocyanate (NCO) amount in thermoplastic polyurethane, and melting of thermoplastic polyurethane at 180 ° C A pellet of the polyacetal resin composition was produced in the same manner as in Example 1 except that the viscosity was as shown in Table 1 or Table 2.
In Tables 1 and 2, nine types of (B-1) to (B-9) were used as the thermoplastic polyurethane (B). In Tables 1 and 2, the following were used as formaldehyde scavengers (C-1), (C-2), and (C-3), respectively.
(C-1) dodecanedioic acid dihydrazide (C-2) stearic acid hydrazide (C-3) benzoguanamine

[Characteristic evaluation]
(1) Effect of suppressing the amount of formaldehyde generated About the effect of suppressing the amount of formaldehyde generated, the amount of formaldehyde generated was measured and evaluated based on the amount of formaldehyde generated.
The amount of formaldehyde generated was measured as follows.
<Fabrication of flat specimen>
First, pellets of the polyacetal resin compositions obtained in Examples 1 to 9 and Comparative Examples 1 to 9 were used at a cylinder temperature of 215 ° C. and a mold temperature of 80 ° C. using an injection molding machine PS-40 manufactured by Nissei Plastic Industries. Injection molding was performed to prepare a 100 mm × 40 mm × 2 mm flat plate test piece.
<Measurement of formaldehyde generation>
Then, on the day after the day of producing the flat plate test piece, the flat plate test piece was compliant with the method described in German Automobile Manufacturers Association Standard VDA275 (automobile interior parts-determination of formaldehyde emission by the revised flask method). The formaldehyde generation amount was measured by the following method.
(I) First, 50 ml of distilled water was put in a polyethylene container, the lid was closed with the flat plate test piece suspended in the air, and heated in a sealed state at 60 ° C. for 3 hours.
(Ii) After leaving at room temperature for 60 minutes, a flat plate test piece was taken out.
(Iii) The amount of formaldehyde absorbed in distilled water in a polyethylene container was measured by a acetylacetone colorimetric method using a UV spectrometer, and this amount of formaldehyde was defined as the amount of formaldehyde generated. The results are shown in Tables 1 and 2.
In Tables 1 and 2, the amount of formaldehyde generated was expressed as a relative value using the amount of formaldehyde generated in (Comparative Example 1) as the reference value (1.00). The acceptance criteria for the formaldehyde generation inhibitory effect were as follows.
-Formaldehyde generation amount is 0.25 or less: Pass-Formaldehyde generation amount exceeds 0.25: Fail

(2) Impact resistance The impact resistance of the polyacetal resin composition was evaluated based on the measured value by measuring the notched Charpy impact strength of the polyacetal resin composition.
The notched Charpy impact strength was measured as follows.
<Preparation of notched Charpy test specimen>
First, pellets of the polyacetal resin composition obtained in Examples 1 to 9 and Comparative Examples 1 to 9 were injected at a cylinder temperature of 195 ° C. and a mold temperature of 90 ° C. using an injection molding apparatus EC-100S manufactured by Toshiba Machine. Molded to prepare a 4 mm thick ISO No. 1 dumbbell test piece described in JIS K7113.
Next, the dumbbell test piece was cut according to the method described in JIS K7113-1 / 1A to obtain a notched Charpy test piece.
<Measurement of notched Charpy impact strength>
Using the notched Charpy test specimen, the notched Charpy impact strength was measured by an edgewise parallel test method in accordance with the method described in ISO-179. The results are shown in Tables 1 and 2. The acceptance criteria for the notched Charpy impact strength were as follows.
・ Charpy impact strength with notch is 18 kJ / m ² or more: Pass ・ Charpy impact strength with notch is less than 18 kJ / m ² : Fail

  As shown in Table 1 and Table 2, it was found that Examples 1 to 9 all met the acceptance criteria in terms of formaldehyde generation suppression effect and impact resistance. On the other hand, it was found that Comparative Examples 1 to 9 did not satisfy the acceptance criteria in terms of formaldehyde generation amount or impact resistance.

Therefore, according to the polyacetal resin composition of this invention, it was confirmed that it has the outstanding impact resistance and can fully suppress generation | occurrence | production of formaldehyde.

Claims (2)

To 100 parts by mass of polyacetal resin (A), 1 to 120 parts by mass of thermoplastic polyurethane (B), 0.01 to 5 parts by mass of formaldehyde scavenger (C) having formaldehyde-reactive nitrogen,
A polyacetal resin composition in which the thermoplastic polyurethane contains a residual isocyanate amount of 0.10% by mass or less, has a moisture content of 3000 ppm by mass or less, and exhibits a melt viscosity of 200,000 poise or more at 180 ° C.   A molded article formed by molding the polyacetal resin composition according to claim 1.