MASTER BATCH FOR EXPANSION MOLDING AND FOAM MOLDED BODY

Abstract

The present invention aims to provide a masterbatch for foam molding which can be suitably used in molding involving high shear force or molding requiring low molding temperature and which can provide a foam molded article having a high expansion ratio and good appearance quality. The present invention also aims to provide a foam molded article formed from the masterbatch for foam molding. Provided is a masterbatch for foam molding, containing: a base resin; and a thermally expandable microcapsule, the masterbatch having a true specific gravity of 0.80 g/cm.sup.3 or more, the base resin containing an olefin elastomer, the masterbatch containing the thermally expandable microcapsule in an amount of 40 to 300 parts by weight relative to 100 parts by weight of the base resin.

Claims

1. A masterbatch for foam molding, comprising: a base resin; and a thermally expandable microcapsule, the masterbatch having a true specific gravity of 0.80 g/cm.sup.3 or more, the base resin containing an olefin elastomer, the masterbatch containing the thermally expandable microcapsule in an amount of 40 to 300 parts by weight relative to 100 parts by weight of the base resin.

2. The masterbatch for foam molding according to claim 1, wherein the olefin elastomer has a melt index of 2 to 30 g/10 min.

3. The masterbatch for foam molding according to claim 1, wherein the olefin elastomer has a melting point of 50 C. to 120 C.

4. The masterbatch for foam molding according to claim 1, wherein the thermally expandable microcapsule includes: a shell containing a polymer; and a volatile expansion agent as a core agent encapsulated by the shell, and the shell contains a polymer obtained by polymerizing a monomer mixture that contains a polymerizable monomer (I) containing at least one selected from acrylonitrile, methacrylonitrile, and vinylidene chloride.

5. The masterbatch for foam molding according to claim 1, wherein the shell contains a polymer obtained by polymerizing a monomer mixture that contains 40 to 90% by weight of a polymerizable monomer (I) containing at least one selected from acrylonitrile, methacrylonitrile, and vinylidene chloride and 5 to 50% by weight of a radically polymerizable unsaturated carboxylic acid monomer (II) having a carboxy group and having a carbon number of 3 to 8.

6. The masterbatch for foam molding according to claim 1, wherein the monomer mixture contains 40 to 90% by weight of a polymerizable monomer (I) containing at least one selected from acrylonitrile, methacrylonitrile, and vinylidene chloride and 5 to 50% by weight of a radically polymerizable unsaturated carboxylic acid monomer (II) having a carboxy group and having a carbon number of 3 to 8, and the monomer mixture is free of a polymerizable monomer (III) having two or more double bonds in a molecule.

7. The masterbatch for foam molding according to claim 1, wherein the monomer mixture contains 40 to 90% by weight of a polymerizable monomer (I) containing at least one selected from acrylonitrile, methacrylonitrile, and vinylidene chloride, 5 to 50% by weight of a radically polymerizable unsaturated carboxylic acid monomer (II) having a carboxy group and having a carbon number of 3 to 8, and 0.2% by weight or less of a polymerizable monomer (III) having two or more double bonds in a molecule and/or 0.1 to 10% by weight of a metal cation hydroxide (IV).

8. The masterbatch for foam molding according to claim 1, wherein the monomer mixture contains 40 to 90% by weight of a polymerizable monomer (I) containing at least one selected from acrylonitrile, methacrylonitrile, and vinylidene chloride, 5 to 50% by weight of a radically polymerizable unsaturated carboxylic acid monomer (II) having a carboxy group and having a carbon number of 3 to 8, and 0.1 to 10% by weight of a metal cation hydroxide (IV), and the monomer mixture is free of a polymerizable monomer (III) having two or more double bonds in a molecule.

9. The masterbatch for foam molding according to claim 1, wherein the thermally expandable microcapsule has a maximum foaming temperature of 180 C. or higher.

10. A foam molded article formed from the masterbatch for foam molding according to claim 1.

Description

DESCRIPTION OF EMBODIMENTS

[0151] Embodiments of the present invention are more specifically described in the following with reference to, but not limited to, examples.

(Production of Thermally Expandable Microcapsule)

[0152] A polymerization reaction container was charged with 300 parts by weight of water, 89 parts by weight of sodium chloride as an adjustor, 0.07 parts by weight of sodium nitrite as a water-soluble polymerization inhibitor, 8 parts by weight of colloidal silica (available from Asahi Denka) as a dispersion stabilizer, and 0.3 parts by weight of polyvinylpyrrolidone (available from BASF), whereby an aqueous dispersion medium was prepared. Subsequently, the aqueous dispersion medium was mixed with an oily mixture containing a metal salt, monomers, a volatile expansion agent, and a polymerization initiator in the amounts shown in Table 1, whereby a dispersion was prepared. The total dispersion was 15 kg. The obtained dispersion was stirred and mixed with a homogenizer, fed to a pressure polymerization vessel (20 L) purged with nitrogen, pressurized (0.2 MPa), and reacted at 60 C. for 20 hours to give a reaction product. The obtained reaction product was repeatedly dehydrated and water-washed with a centrifuge, and dried to give thermally expandable microcapsules (Nos. 1 to 3).

[0153] In Table 1, the polymerizable monomer (I) is denoted as Monomer (I), the radically polymerizable unsaturated carboxylic acid monomer (II) as Monomer (II), and the polymerizable monomer (III) as Monomer (III).

Examples 1 to 8 and Comparative Examples 1 to 5

(Production of Masterbatch Pellets)

[0154] An amount of 100 parts by weight of the base resin shown in Table 2 was kneaded with 10 parts by weight of a fatty acid ester as a lubricant with a Banbury mixer. When about 100 C. was reached, the obtained thermally expandable microcapsules were added in the amount shown in Table 2, followed by kneading for additional 30 seconds. The kneaded product was extruded and pelletized at the same time, whereby masterbatch pellets were obtained. In Table 2, EMMA denotes ethylene-methyl methacrylate copolymer. LDPE denotes low density polyethylene.

[0155] The following olefin elastomers (TPOs, propylene elastomers) were used.

[0156] Propylene elastomer [TPO (1)]: melt index: 3.7 g/10 min, melting point: 75 C., propylene content: 91% by weight, ethylene content: 9% by weight

[0157] Propylene elastomer [TPO (2)]: melt index: 3.6 g/10 min, melting point: 65 C., propylene content: 89% by weight, ethylene content: 11% by weight

[0158] Propylene elastomer [TPO (3)]: melt index: 20 g/10 min, melting point: 65 C., propylene content: 87% by weight, ethylene content: 13% by weight

[0159] Ethylene elastomer [TPO (4)]: melt index: 5 g/10 min, melting point: 59 C., ethylene content: 24% by weight, 1-octene content: 76% by weight

(Production of Foam Molded Article)

[0160] An amount of 3 parts by weight of the obtained masterbatch pellets were mixed with 100 parts by weight of an olefin elastomer (available from Mitsui Chemicals, Inc., MILASTOMER 7030BS). The mixed pellets were fed to a hopper of an extruder, melted and kneaded, and extrusion molded into a sheet form molded article. The extrusion was performed at a mold temperature of 190 C.

(Evaluation)

[0161] The thermally expandable microcapsules (Nos. 1 to 3) and the molded articles obtained in Examples 1 to 8 and Comparative Examples 1 to 5 were evaluated for the following properties. Table 1 and Table 2 show the results.

(1) Evaluation of Thermally Expandable Microcapsules

(1-1) Volume Average Particle Size

[0162] The volume average particle size was measured with a particle size distribution analyzer (LA-910, available from HORIBA, Ltd.).

(1-2) Foaming Starting Temperature, Maximum Foaming Temperature, and Maximum Displacement

[0163] The foaming starting temperature (Ts), maximum displacement (Dmax), and maximum foaming temperature (Tmax) were measured with a thermomechanical analyzer (TMA) (TMA2940, available from TA Instruments). Specifically, 25 g of a sample was placed in an aluminum container having a diameter of 7 mm and a depth of 1 mm, and heated at a temperature increase rate of 5 C./min from 80 C. to 220 C. with a force of 0.1 N applied from the top. The displacement was measured in the perpendicular direction of a measuring terminal. The temperature at which the displacement began to increase was defined as the foaming starting temperature. The maximum value of the displacement was defined as the maximum displacement. The temperature at which the maximum displacement was obtained was defined as the maximum foaming temperature.

TABLE-US-00001 TABLE 1 {circle around (1)} {circle around (2)} {circle around (3)} Thermally Amount Monomer (I) Acrylonitrile 20 20 70 expandable (parts by Methacrylonitrile 30 30 30 microcapsule weight) Monomer (II) Methacrylic acid 30 30 0 Monomer (III) Trimethylolpropane trimethacrylate 0 0 0.4 Metal salt (IV) Zinc hydroxide 1.5 1.5 0 Other monomers Methyl methacrylate 20 20 0 Volatile expansion Isopentane 15 0 25 agent Isooctane 10 25 0 Polymerization 2,2-Azobisisobutyronitrile 0.8 0.8 0.8 initiator 2,2-Azobis(4-methoxy-2,4- 0.6 0.6 0.6 dimethylvaleronitrile) Volume average particle size (m) 24 28 26 Foaming starting temperature (Ts) ( C.) 174 210 120 Maximum foaming temperature (Tmax) ( C.) 218 230 165 Maximum displacement (Dmax) (m) 800 800 1000

(2) Evaluation of Masterbatch Pellet

(2-1) Measurement of True Specific Gravity

[0164] The true specific gravity of the masterbatch pellets was measured by a method in conformity with Method A (water displacement method) of JIS K 7112 with a densimeter MD-200S (available from Alfa Mirage, Co., Ltd.).

(2-2) Measurement of Bulk Specific Gravity

[0165] The bulk specific density was measured by a method in conformity with JIS K 6721.

(2-3) Measurement of Masterbatch Size

[0166] Thirty pellets were randomly collected from the obtained masterbatch pellets. The total weight of the 30 pellets was measured.

(3) Evaluation of Molded Article

(3-1) Density and Expansion Ratio

[0167] The density before foaming and the density of the obtained molded article (after foaming) were measured by a method in conformity with Method A (water displacement method) of JIS K 7112.

[0168] The expansion ratio was calculated from the density of the molded article before and after foaming.

(3-2) Surface Properties

[0169] The surface roughness (Rz) of the molded article surface was measured with a 3D shape form measurement system (available from Keyence Corporation). The surface properties were evaluated according to the following criteria.

(Good): The measured Rz value was less than 50 m.
(Fair): 50 m Rz value 100 m
x (Poor): The measured Rz value was more than 100 m.

(3-3) Dispersibility

[0170] A cross section of the obtained molded article was visually observed with an electron microscope. The dispersibility of the thermally expandable microcapsules was evaluated according to the following criteria.

(Good): Cell distribution was uniform.
x (Poor): Cell distribution was not uniform.

TABLE-US-00002 TABLE 2 Example (1) (2) (3) (4) (5) (6) (7) Thermally expandable microcapsule No. {circle around (1)} {circle around (1)} {circle around (1)} {circle around (1)} {circle around (2)} {circle around (2)} {circle around (1)} Base resin used in Type TPO (1) TPO (2) TPO (3) TPO (4) TPO (1) TPO (2) TPO (1) masterbatch Melt index (g/10 min) 3.7 3.6 20 5 3.7 3.6 3.7 Melting point ( C.) 75 65 65 59 75 65 75 Ts - melting point of base resin ( C.) 99 109 109 115 135 145 99 Tmax - melting point of base resin ( C.) 143 153 153 159 155 165 143 Amount of thermally expandable microcapsules in 100 100 100 100 100 100 50 masterbatch relative to 100 parts by weight of base resin (parts by weight) Amount of masterbatch in molded article 3 3 3 3 3 3 3 relative to 100 parts by weight of olefin elastomer (parts by weight) Masterbatch True specific gravity (g/cm.sup.3) 0.92 0.93 0.92 0.93 0.93 0.91 0.91 evaluation Bulk specific gravity (g/cm.sup.3) 0.44 0.42 0.43 0.42 0.42 0.41 0.41 Masterbatch size (mg/30 pcs) 490 480 470 480 470 480 470 Molded article Density (g/cm.sup.3) 0.68 0.68 0.7 0.69 0.72 0.73 0.73 evaluation Expansion ratio 1.29 1.29 1.26 1.28 1.22 1.21 1.21 Surface properties Dispersibility Example Comparative Example (8) (1) (2) (3) (4) (5) Thermally expandable microcapsule No. {circle around (1)} {circle around (1)} {circle around (1)} {circle around (1)} {circle around (1)} Base resin used in Type TPO (1) TPO (1) TPO (1) LDPE EMMA TPO (1) masterbatch Melt index (g/10 min) 3.7 3.7 3.7 55 450 3.7 Melting point ( C.) 75 75 75 105 67 75 Ts - melting point of base resin ( C.) 99 99 99 69 107 45 Tmax - melting point of base resin ( C.) 143 143 143 113 151 90 Amount of thermally expandable microcapsules in 200 30 500 100 100 100 masterbatch relative to 100 parts by weight of base resin (parts by weight) Amount of masterbatch in molded article 3 3 3 3 3 3 relative to 100 parts by weight of olefin elastomer (parts by weight) Masterbatch True specific gravity (g/cm.sup.3) 0.93 0.90 Masterbatch 0.95 0.93 0.73 evaluation Bulk specific gravity (g/cm.sup.3) 0.44 0.41 producion 0.4 0.39 0.33 Masterbatch size (mg/30 pcs) 490 460 failed 470 470 350 Molded article Density (g/cm.sup.3) 0.63 0.81 0.67 0.69 0.79 evaluation Expansion ratio 1.40 1.09 1.31 1.28 1.11 Surface properties x Dispersibility x x x

INDUSTRIAL APPLICABILITY

[0171] The present invention can provide a masterbatch for foam molding which can be suitably used in molding involving high shear force or molding requiring low molding temperature and which can provide a foam molded article having a high expansion ratio and good appearance quality. The present invention also aims to provide a foam molded article formed from the masterbatch for foam molding.