Resin composition for injection molding

Abstract

The present invention provides a resin composition for injection molding that can provide a molded body having excellent thermal stability, excellent thermal fluidity, and high water pressure resistance without a heavy metal such as lead or tin. The present invention also provides a molded body including the resin composition for injection molding. Provided is a resin composition for injection molding containing: a chlorinated polyvinyl chloride; polyvinyl chloride; and a thermal stabilizer, the thermal stabilizer containing a calcium alkyl carboxylate and a zinc compound, the polyvinyl chloride having a degree of polymerization of 400 to 1,000, the resin composition containing the polyvinyl chloride in an amount of 1 to 30 parts by mass relative to 100 parts by mass of the chlorinated polyvinyl chloride.

Claims

1. A resin composition for injection molding comprising: a chlorinated polyvinyl chloride; a polyvinyl chloride; and a thermal stabilizer, the thermal stabilizer comprising a calcium alkyl carboxylate and a zinc compound, the polyvinyl chloride having a degree of polymerization of 400 to 800, the resin composition comprising the polyvinyl chloride in an amount of 1 to 30 parts by mass relative to 100 parts by mass of the chlorinated polyvinyl chloride, wherein the chlorinated polyvinyl chloride and the polyvinyl chloride have an average chlorine content of 65 to 68% by mass, and the chlorinated polyvinyl chloride and the polyvinyl chloride have a difference in degree of polymerization of 200 or less.

2. The resin composition for injection molding according to claim 1, wherein the chlorinated polyvinyl chloride has structural units (a) to (c) represented by the following formulae (a) to (c): [Chem. 1]
—CCl.sub.2—  (a),
—CHCl—  (b),
—CH.sub.2—  (c), the proportion of the structural unit (a) is 17.5 mol % or less, the proportion of the structural unit (b) is 46.0 mol % or more, and the proportion of the structural unit (c) is 37.0 mol % or less, relative to the total number of moles of the structural units (a), (b), and (c).

3. The resin composition for injection molding according to claim 1, wherein the chlorinated polyvinyl chloride has a degree of polymerization of 500 to 800.

4. The resin composition for injection molding according to claim 1, wherein the chlorinated polyvinyl chloride has a chlorine content of 63 to 72% by mass.

5. The resin composition for injection molding according to claim 1, comprising the thermal stabilizer in an amount of 0.4 to 20 parts by mass relative to 100 parts by mass of the chlorinated polyvinyl chloride.

6. The resin composition for injection molding according to claim 1, further comprising an antioxidant.

7. The resin composition for injection molding according to claim 1, which is free from β-diketone.

8. A molded body molded from the resin composition for injection molding according to claim 1.

9. The resin composition for injection molding according to claim 1, wherein the polyvinyl chloride has a degree of polymerization of 400 to 700.

Description

Description of Embodiments

(1) The present invention will be hereinafter described in more detail with reference to examples; however, the invention should not be construed as being limited to these examples.

EXAMPLE 1

(2) (Preparation of Chlorinated Polyvinyl Chloride)

(3) A glass-lined reaction vessel with an internal volume of 300 L was charged with 200 kg of ion-exchange water and 56 kg of a polyvinyl chloride with an average degree of polymerization of 700. The mixture was stirred, and water was further added to the reaction vessel to disperse the mixture in the water. The pressure was subsequently reduced to remove oxygen from the reaction vessel, and the temperature was simultaneously elevated to 90° C.

(4) Chlorine was then supplied into the reaction vessel so that the chlorine partial pressure would be 0.4 MPa, and the chlorination reaction was performed while adding 0.2% by mass hydrogen peroxide at a rate of 1 part by mass per hour (320 ppm/hour). The reaction was continued until the chlorine content of the chlorinated polyvinyl chloride reached 67.3% by mass. When the chlorine content of the chlorinated polyvinyl chloride reached 62.3% by mass (five percentage points by mass lower than the final chlorine content), the amount of 0.2% by mass hydrogen peroxide added was reduced to 0.1 parts by mass per hour (200 ppm/hour), and the average chlorine consumption rate was adjusted to 0.012 kg/PVC-kg.Math.5 min, and then the chlorination was allowed to proceed. Further, when the chlorine content reached 65.3% by mass (three percentage points by mass lower than the final chlorine content), the amount of 0.2% by mass hydrogen peroxide added was reduced to 150 ppm/hour, and the average chlorine consumption rate was adjusted to 0.008 kg/PVC-kg.Math.5 min, and then the chlorination was allowed to proceed. In this way, a chlorinated polyvinyl chloride having a chlorine content of 67.3% by mass was obtained. The chlorine content was measured in accordance with JIS K 7229.

(5) (Preparation of Resin Composition for Injection Molding)

(6) To 100 parts by mass of the obtained chlorinated polyvinyl chloride (degree of polymerization: 700) were added 7 parts by mass of a polyvinyl chloride (chlorine content: 56.7% by mass, degree of polymerization: 700), 4 parts by mass of a thermal stabilizer, and 0.5 parts by mass of an antioxidant, followed by mixing. The thermal stabilizer used contained 2.0 parts by mass of calcium stearate and 2.0 parts by mass of zinc stearate. The antioxidant used was pentaerythrityl-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] (hindered phenolic antioxidant, Irganox 1010, available from BASF, loss in quantity on heating at 200° C.: 1.0% by mass).

(7) Furthermore, 5.0 parts by mass of an impact resistance modifier, 2.0 parts by mass of a polyethylene lubricant (available from Mitsui Chemicals, Inc., Hiwax 220 MP), 0.3 parts by mass of a fatty acid ester lubricant (available from Emery Oleochemicals Japan Ltd., LOXIOL G-32), and 5.0 parts by mass of titanium dioxide (available from Ishihara Sangyo Kaisha, Ltd., TIPAQUE CR-90) were added. The impact resistance modifier used was MBS (methacrylic butadiene styrene) resin (available from Kaneka Corporation, Kane Ace M-511). They were then uniformly mixed in a super mixer to give a resin composition for injection molding.

(8) (Preparation of Injection Molded Body)

(9) The obtained resin composition for injection molding was fed into a twin-screw counter-rotating conical extruder with a diameter of 30 mm (Osada Seisakusho; “OSC-30”) to prepare pellets at a resin temperature of 190° C.

(10) The obtained pellets were fed into an injection molding machine (available from Nippon Steel Nisshin Co., Ltd. “J100E-C5”) to prepare a socket-shaped injection molded body having a nominal diameter of 25 mm. The resin temperature when the resin was purged from the nozzle was 230° C.

EXAMPLE 2

(11) A resin composition for injection molding and an injection molded body were prepared as in Example 1 except that the amount of the polyvinyl chloride added was changed to 3 parts by mass.

EXAMPLE 3

(12) A resin composition for injection molding and an injection molded body were prepared as in Example 1 except that the amount of the polyvinyl chloride added was changed to 25 parts by mass.

EXAMPLE 4

(13) A chlorinated polyvinyl chloride, a resin composition for injection, molding, and an injection molded body were prepared as in Example 1 except that the polyvinyl chloride was changed to a polyvinyl chloride (chlorine content: 56.7% by mass, degree of polymerization: 1,000).

EXAMPLE 5

(14) A resin composition for injection molding and an injection molded body were produced as in Example 1 except that the amount of the polyvinyl chloride added was changed to 18 parts by mass.

EXAMPLE 6

(15) A resin composition for injection molding and an injection molded body were prepared as in Example 1 except that the chlorinated polyvinyl chloride was changed to a chlorinated polyvinyl chloride (chlorine content: 67.3% by mass, degree of polymerization: 600).

EXAMPLE 7

(16) A resin composition for injection molding and an injection molded body were prepared as in Example 1 except that the chlorinated polyvinyl chloride was changed to a chlorinated polyvinyl chloride (chlorine content: 67.3% by mass, degree of polymerization: 500).

EXAMPLE 8

(17) A chlorinated polyvinyl chloride, a resin composition for injection molding, and an injection molded body were prepared as in Example 1 except that the polyvinyl chloride was changed to a polyvinyl chloride (chlorine content: 56.7% by mass, degree of polymerization: 500).

COMPARATIVE EXAMPLE 1

(18) A resin composition for injection molding and an injection molded body were prepared as in Example 1 except that the polyvinyl chloride was not added, and that the thermal stabilizer was changed to 2.0 parts by mass calcium montanate and 2.0 parts by mass of zinc laurate.

COMPARATIVE EXAMPLE 2

(19) A resin composition for injection molding and an injection molded body were produced as in Example 1 except that the amount of the polyvinyl chloride added was changed to 35 parts by mass.

COMPARATIVE EXAMPLE 3

(20) A resin composition for injection molding and an injection molded body were prepared as in Example 1 except that the type of the polyvinyl chloride was changed to a polyvinyl chloride (chlorine content: 56.7% by mass, degree of polymerization: 1,300) and the amount thereof was changed to 7 parts by mass, and that other components added were changed to those shown in Table 1.

COMPARATIVE EXAMPLE 4

(21) A resin composition for injection molding and an injection molded body were prepared as in Example 1 except that the amount of the polyvinyl chloride added was changed to 0.5 parts by mass, and that other components added were changed to those shown in Table 1.

(22) <Evaluation>

(23) The resin compositions for injection molding and molded bodies obtained in the examples and the comparative examples were evaluated as follows. Table 1 shows the results.

(24) [Evaluation of Resin Composition for Injection Molding]

(25) <Static Thermal Stability>

(26) The obtained chlorinated polyvinyl chloride composition was fed to two 8-inch rolls and kneaded at 205° C. for three minutes to prepare a 1.0-mm-thick sheet. The obtained sheet was heated in a gear oven at 200° C. The time (minutes) before the sheet foamed or became blackened was measured.

(27) <Ease of Gelling and Time to Reach Decomposition Temperature>

(28) The obtained chlorinated polyvinyl chloride composition was fed into a plastomill (available from Toyo Seiki Seisaku-Sho, Ltd., “Labo PlastoMill”) and kneaded at a rotation rate of 50 rpm, 195° C., and a loading of 63 g to measure the gelling time (seconds). The gelling time was the time from the start of kneading until the kneading torque reached its peak. After the gelling, kneading and heating were continued to measure the decomposition time (minutes) of the chlorinated polyvinyl chloride. The time from the start of kneading until the resin temperature, which became stable after the gelling, started to rise again was taken as the time to reach decomposition temperature.

(29) <Mechanical Physical Properties (Tensile Strength and Thermal Deformation Temperature)>

(30) The obtained chlorinated polyvinyl chloride composition was fed to two 8-inch rolls, kneaded at 205° C. for 3 minutes, and formed into 1.0-mm-thick sheets. The obtained sheets were layered, pre-heated with a press at 205° C. for 3 minutes, and pressurized for 4 minutes to prepare a 3-mm-thick press plate. The obtained press plate was cut into specimens by machining. With these specimens, the tensile strength and the tensile modulus of elasticity were measured in accordance with ASTM D638, and the thermal deformation temperature was measured in accordance with ASTM D648 at a load of 186 N/cm.sup.2. The thermal deformation temperature was measured after annealing the obtained press plate in a gear oven at 90° C. for 24 hours.

(31) <Flow Evaluation>

(32) Flow evaluation was performed using Shimadzu Flowtester (CFT-500D/100D, available from SHIMADZU Corp.). Specifically, the roll sheet prepared in <Mechanical physical properties (tensile strength and thermal deformation temperature)> was cut into about 5 mm square pieces. The pieces were fed into the barrel heated to 210° C. and extruded through a capillary having a die diameter of 1 mm and a die length of 10 mm at a load of 205 kgf. Then, the measurement was started when 3 mm of the molten resin was extruded from the capillary, and the time (seconds) taken per millimeter of extrusion was measured.

(33) A measured value of 0.2 mm/sec or more was evaluated as “Passed”. A measured value of less than 0.2 mm/sec was evaluated as “Failed”.

(34) [Evaluation of Molded Body]

(35) <Appearance Observation>

(36) The socket-shaped injection molded body was evaluated for the presence or absence of bubbles (foaming), the presence or absence of silver streaks, and the presence or absence of scorching (discoloration).

(37) The depth of a weld of the obtained socket-shaped injection molded body was measured with One-Shot 3D Measuring Macroscope (available from Keyence Corporation, VR-3000).

(38) <Water Pressure Resistance Test>

(39) The Water pressure resistance was evaluated as “Passed” or “Failed” by a method in accordance with “Test for resistance to hydraulic pressure” in ASTM D1599.

(40) TABLE-US-00001 TABLE 1 Examples 1 2 3 4 5 6 Composition Chlorinated polyvinyl chloride (degree of polymerization 500) — — — — — — (parts by mass) Chlorinated polyvinyl chloride (degree of polymerization 600) — — — — — 100 Chlorinated polyvinyl chloride (degree of polymerization 700) 100 100 100 100 100 — Polyvinyl chloride (degree of polymerization 500) — — — — — — Polyvinyl chloride (degree of polymerization 700) 7 3 25 — 18 7 Polyvinyl chloride (degree of polymerization 1000) — — — 7 — — Polyvinyl chloride (degree of polymerization 1300) — — — — — — Calcium stearate 2.0 2.0 2.0 2.0 2.0 2.0 Calcium montanate — — — — — — Zinc stearate 2.0 2.0 2.0 2.0 2.0 2.0 Zinc laurate — — — — — — Hindered phenolic antioxidant 0.5 0.5 0.5 0.5 0.5 0.5 Methacrylic butadiene styrene resin 5.0 5.0 5.0 5.0 5.0 5.0 Polyethylene lubricant 2.0 2.0 2.0 2.0 2.0 2.0 Fatty acid ester lubricant 0.3 0.3 0.3 0.3 0.3 0.3 Titanium dioxide 5.0 5.0 5.0 5.0 5.0 5.0 Average chlorine content (% by mass) 66.6 67.0 65.2 66.6 65.7 66.6 Difference in degree of polymerization 0 0 0 300 0 100 Evaluation Thermal stability Static thermal stability (minutes) 100 100 90 100 90 100 (chlorinated Process Ease of gelling [time (seconds)] 89 90 80 90 85 85 polyvinyl characteristics Time to reach decomposition temperature [(minutes)] 17 17 19 16 18 17 chloride Mechanical Tensile strength (Mpa) 53.0 53.0 54.0 53.0 54.0 53.0 composition) properties Thermal deformaion temperature (° C.) 108 108 101 108 105 108 Fluidity Flow evaluation Passed Passed Passed Passed Passed Passed Evaluation Molding quality Foaming Absent Absent Absent Absent Absent Absent (molded Silver streak Absent Absent Absent Absent Absent Absent product) Scorching Absent Absent Absent Absent Absent Absent Weld depth [μm] 10 15 4 18 8 4 Water pressure Water pressure resistance test Passed Passed Passed Passed Passed Passed resistance evaluation Examples Comparative Examples 7 8 1 2 3 4 Composition Chlorinated polyvinyl chloride (degree of polymerization 500) 100 — — — — — (parts by mass) Chlorinated polyvinyl chloride (degree of polymerization 600) — — — — — — Chlorinated polyvinyl chloride (degree of polymerization 700) — 100 100 100 100 100 Polyvinyl chloride (degree of polymerization 500) — 7 — — — — Polyvinyl chloride (degree of polymerization 700) 7 — — 35 — 0.5 Polyvinyl chloride (degree of polymerization 1000) — — — — — — Polyvinyl chloride (degree of polymerization 1300) — — — — 7 — Calcium stearate 2.0 2.0 — 2.0 3.0 2.0 Calcium montanate — — 2.0 — — — Zinc stearate 2.0 2.0 — 2.0 3.0 2.0 Zinc laurate — — 2.0 — — — Hindered phenolic antioxidant 0.5 0.5 0.5 0.5 0.5 0.5 Methacrylic butadiene styrene resin 5.0 5.0 5.0 5.0 5.0 5.0 Polyethylene lubricant 2.0 2.0 2.0 2.0 2.0 2.0 Fatty acid ester lubricant 0.3 0.3 0.3 0.3 0.3 0.3 Titanium dioxide 5.0 5.0 5.0 5.0 5.0 5.0 Average chlorine content (% by mass) 66.6 66.6 67.3 64.6 66.6 67.2 Difference in degree of polymerization 200 300 — 0 600 0 Evaluation Thermal stability Static thermal stability (minutes) 100 90 100 90 90 90 (chlorinated Process Ease of gelling [time (seconds)] 80 75 95 80 92 92 polyvinyl characteristics Time to reach decomposition temperature [(minutes)] 17 16 15 20 15 15 chloride Mechanical Tensile strength (Mpa) 53.0 52.0 53.0 56.0 53.0 53.5 composition) properties Thermal deformaion temperature (° C.) 108 108 108 90 108 108 Fluidity Flow evaluation Passed Passed Failed Passed Failed Failed Evaluation Molding quality Foaming Absent Absent Absent Absent Absent Present (molded Silver streak Absent Absent Present Absent Present Present product) Scorching Absent Absent Present Absent Present Present Weld depth [μm] 5 4 22 2 30 20 Water pressure Water pressure resistance test Passed Passed Passed Passed Failed Failed resistance evaluation

INDUSTRIAL APPLICABILITY

(41) The present invention can provide a resin composition for injection molding that can provide a molded body having excellent thermal stability, excellent thermal fluidity, and high water pressure resistance without a heavy metal such as lead or tin. The present invention can also provide a molded body including the resin composition for injection molding.