Thermoplastic resin foamed particles of the present invention including more than one or more functional additive selected from inorganic powder and inorganic fibers each includes a core layer formed of a thermoplastic resin and a coating layer in a foamed state formed of a thermoplastic resin, the mass ratio of the coating layer to the core layer is 99:1 to 50:50, the content (X) of the functional additive in the core layer is 5 to 90% by mass, and the content of the functional additive in the coating layer is smaller than the content (X) of the functional additive in the core layer. By this way, thermoplastic resin foamed particles from which a homogeneous foamed particle molding having excellent dimension stability, fusibility and appearance can be obtained while containing functional additive are provided.
|
1. Thermoplastic resin foamed particles comprising more than one or more functional additive selected from inorganic powder and inorganic fibers, wherein
each particle comprises a core layer formed of a thermoplastic resin and a coating layer in a foamed state formed of a thermoplastic resin,
the mass ratio of the coating layer to the core layer is 99:1 to 50:50,
the content (X) of the functional additive in the core layer is 5 to 90% by mass, and
the content of the functional additive in the coating layer is smaller than the content (X) of the functional additive in the core layer.
2. The thermoplastic resin foamed particles according to
3. The thermoplastic resin foamed particles according to
4. The thermoplastic resin foamed particles according to
5. The thermoplastic resin foamed particles according to
6. The thermoplastic resin foamed particles according to
|
|||||||||||||||||||||||||||||||
The present invention relates to thermoplastic resin foamed particles containing functional additive.
Thermoplastic resin foamed particles can be molded into various shapes according to use by in-mold molding. Thermoplastic resin foamed particle molding obtained from said foamed particles by in-mold molding are used in a wide variety of use such as dielectric bodies, electric wave shielding bodies, heat insulating materials, packaging materials for electronic parts, shock absorbing materials and reusable containers.
For example, Patent Literatures 1 and 2 describe that foamed particle molding containing functional additive such as inorganic powder and inorganic fibers are used as dielectric bodies and electric wave absorbers.
Patent Literature 1: JP 2008-512502 W
Patent Literature 2: JP H04-56298 A
However, as described in Patent Literature 1, in a case where the thermoplastic resin foamed particles contained functional additive in a large amount, it was possible that the secondary foamability of the foamed particles decreases and thus the fusibility and appearance of a foamed particle molding may decrease. Therefore, in such case, problems remained in productivity so as to obtain a fine molding, for example, it was necessary to increase the molding pressure during the in-mold molding, and it was necessary to pressurize the foamed particles in advance, and the like. Furthermore, in the electric wave absorber described in Patent Literature 2, a foamed particle molding is formed by using foamed particles to which a dielectric body is adhered and foamed particles to which a dielectric body is not adhered. However, in this method, it is difficult to completely and homogeneously mix these two kinds of foamed particles during the molding of the foamed particle molding, and thus problems remained in productivity since there was a possibility that unevenness occurs in the properties among the foamed particle molding, and the production control was difficult.
The present invention was made in view of the abovementioned conventional problems, and aims at providing thermoplastic resin foamed particles from which a homogeneous foamed particle molding having excellent dimension stability, fusibility and appearance can be obtained while containing functional additive.
The present invention provides the thermoplastic resin foamed particles described below.
In the formula,
The average cell diameter of the foamed particles was measured as follows. The average cell diameter was obtained as follows based on an enlarged photograph obtained by photographing under a microscope a cross-sectional surface obtained by cutting one foamed particle at the B-B cross-sectional surface in
Furthermore, in the cross-sectional enlarged photograph of the foamed particle, a curve running at 100 μm inwardly away from the upper end surface of the foamed particle was drawn from the right end surface to the left end surface. Subsequently, the length Ls (μm) of the curve and the number of the cells intersecting with the curve Ns were obtained, and a value obtained by dividing Ls with Ns (Ls/Ns) was set as an average cell diameter of the coating layer 3 in one foamed particle. These operations were conducted on ten foamed particles, and a value obtained by arithmetically averaging the average cell diameters of the core layer 2 and the coating layer 3 of each foamed particle was set as an average cell diameter of the core layer 2 and the coating layer 3 of the foamed particle.
[High Temperature Peak Heat of Fusion of Foamed Particles]
In a DSC curve obtained by heating 1 to 3 mg of the foamed particles by a thermal flux differential scanning calorimeter from 25° C. to 200° C. at a temperature rising rate of 10° C./min (a DSC curve of first heating), an inherent peak Pc having a peak temperature PTmc inherent to the thermoplastic resin appears. Furthermore, more than one endothermic peak Pd having a peak temperature PTmd appears in the high temperature region of said inherent peak. Said endothermic peak Pd is/are the high temperature peak in the present invention, and the surface area of said endothermic peak Pd corresponds to the melting heat of fusion (D) of the high temperature peak of the foamed particles. In addition, the high temperature peak Pd obtained by the retention operation during the above-mentioned production of the foamed particles appears in the DSC curve of the first heating of the foamed particles measured as above, but does not appear in the DSC curve of the second heating obtained when the foamed particles are cooled from 200° C. to 25′C at a cooling rate of 10° C./min after the DSC curve of the first heating is obtained, and heated again at a temperature rising rate of 10° C./min up to 200° C. Therefore, since only a similar endothermic peak to the inherent peak Pc appears in the DSC curve of the second heating, the inherent peak Pc can be easily distinguished from the high temperature peak Pd. The average value of the high temperature peak heat of fusion of five foamed particles (N=5) was deemed as the high temperature peak heat of fusion of the foamed particles.
[Apparent Density of Foamed Particle Molding]
The apparent density of the foamed particle molding was obtained by dividing the mass (g) of the molding by the volume (cm3) obtained from the outside dimension of the molding.
[Fusion Rate of Molding]
The fusion rate of the molding was obtained based on the ratio of the number of the foamed particles that had under-gone material failure among the foamed particles exposed on a broken cross-sectional surface when the foamed particle molding was broken. Specifically, firstly, test pieces were cut out of the foamed particle molding, a cut of about 5 mm was made by a cutter knife in each test piece, and the test piece was broken from the cut part. Secondly, the number (n) of the foamed particles present on the broken cross-sectional surface of the foamed particle molding and the number (b) of the foamed particles that had undergone material failure were measured, and the ratio of (b) to (n) (b/n) was represented by a percentage and deemed as a fusion rate (%).
[Shrinkage Rate]
The shrinkage rate [%] of the foamed particle molding was obtained by ((250 [mm]−the longer side length of the molding [mm])/250 [mm])×100. The “250 [mm]” is the size of the longer side of the molding mold. Furthermore, “the longer side length of the molding [mm]” is a value obtained by curing the foamed particle molding obtained in each of Examples and Comparative Examples under an atmosphere of 80° C. for 12 hours, annealing, and further curing under an atmosphere of 23° C. for 6 hours, and thereafter calculating the length of the longer side of the foamed particle molding.
[Surface Smoothness]
The surface smoothness of the foamed particle molding was evaluated by an observation of the surface of the molding by the unaided eyes.
The secondary foamability of the foamed particle molding was evaluated as follows.
The mechanical strength of the molding was evaluated by measuring the 50% compression strain of the foamed particle molding. Firstly, a test piece was cut out of the central part of the molding into length 50 mm×width 50 mm×thickness 25 mm so that the portions except for the skin layer during the molding has a cubic shape. Secondly, using an AUTOGRAPH AGS-X (manufactured by Shimadzu Corporation) on this test piece, the load at 50% strain was obtained at a compression rate of 10 mm/min according to JIS K 6767 (1999). The 50% compression strain [kPa] was obtained by dividing this load by the pressurized surface area of the test piece.
[Electrostatic Capacity]
The electrostatic capacity of the foamed particles was measured by using a electrostatic capacity meter CM113N manufactured by Yamamoto Electric Instruments. A probe having a detection electrode diameter of 98 mm, a guard electrode outer diameter of 150 mm, an inner diameter of 100 mm, an electrode width of 50 mm, and an insulation distance between electrodes of 2 mm (A1407-8065) was used. Specifically, firstly, a metal plate to be a counter electrode was put on the horizontal surface, and a cylinder made of an insulator of inner diameter 100 mm×outer diameter 150 mm×height 100 mm was put thereon so that the circular part becomes a bottom surface. Secondly, a measurement probe was installed on the cylinder so that any gap is not generated between the guard electrode and the cylinder, and the origin point was adjusted by measuring the electrostatic capacity. The cylinder on the counter electrode was then filled to full leveling with the foamed particles that had been cured under conditions of 23′C and 50% RH for 1 day so that the gaps are minimized, a measurement probe was then put on the cylinder filled with the foamed particles, and the electrostatic capacity of the foamed particles was measured. The measured electrostatic capacity was 0.326 pF in Example 1, and 0.369 pF in Example 2.
[Molding Uniformity]
In the foamed bodies of Examples 1 to 9, the core layers of the foamed particles were highly filled with the functional additives. Furthermore, since the coating layers of the foamed particles were foamed, and the coating layers did not contain the functional additives in a large amount with respect to the core layers, the foamed particles were excellent in the secondary foamability during the in-mold molding. Therefore, it was confirmed that a molding being excellent in fusibility and dimension stability while containing functional additives in a large amount, and also being excellent in appearance, in which the gaps of the foamed particles are filled, and no wrinkles, shrinks and depressions are seen on the surface, was able to be obtained. Accordingly, it can be said that a foamed particle molding having a low shrinkage rate and being excellent in dimension stability can be obtained while utilizing the properties of various functional additives, by using the foamed particles of the present invention in which the functional additives are incorporated.
On the other hand, Comparative Example 1 is an example of a foamed particle molding having a single layer, in which the core layers of the foamed particles are highly filled with the functional additives. Therefore, problems remained in the secondary foamability of the foamed particles and the appearance of the molding, the shrinkage rate of the molding was high, and the molding was poor in dimension stability.
In Comparative Example 2, since the mass ratio of the core layers, which were highly filled with the functional additives, in the foamed particles was high, the foamed particles were poor in secondary foamability, the shrinkage rate of the molding was high, and the molding was poor in dimension stability and appearance.
In Comparative Example 3, the foamed particle molding was formed from the foamed particles formed by mixing the foamed particles 1 and 2 having different functional additive contents. The foamed particles 1, which have a large functional additive content and a dark color, are different in appearance from the foamed particles 2, which have a light color, and thus these foamed particles can be identified. In Comparative Example 3, it was confirmed by a visual observation that the foamed particles 1 were interspersed in the molding, and the molding was heterogeneously constituted. Furthermore, differences were seen in the degrees of dispersion of the foamed particles 1 in the moldings among the plural foamed particle molding prepared by the production method of Comparative Example 3. Moreover, since the difference in molding shrinkage rate and the difference in secondary foamability were significant between the part formed of the foamed particles containing carbon black at a large amount and the part formed of the foamed particles containing carbon black at a small amount in the molding, the obtained molding was poor in secondary foamability and surface smoothness.
Furthermore, since the concentration of the filler material added to the core layers was very high in Comparative Example 4, resin particles were not able to be made, and thus a foamed body was not able to be obtained.
Oikawa, Masaharu, Chiba, Takuya
| Patent | Priority | Assignee | Title |
| Patent | Priority | Assignee | Title |
| 7671820, | Sep 10 2004 | SUMITOMO ELECTRIC INDUSTRIES, LTD | Luneberg dielectric lens and method of producing same |
| 20080108717, | |||
| 20140097389, | |||
| 20150102269, | |||
| 20150158990, | |||
| JP2002003634, | |||
| JP20023634, | |||
| JP2004115785, | |||
| JP2006232939, | |||
| JP2014115785, | |||
| JP4056298, | |||
| JP58145739, | |||
| JP6112735, |
| Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
| Jan 31 2019 | JSP Corporation | (assignment on the face of the patent) | / |
| Date | Maintenance Fee Events |
| Jan 31 2019 | BIG: Entity status set to Undiscounted (note the period is included in the code). |
| Apr 06 2022 | M1551: Payment of Maintenance Fee, 4th Year, Large Entity. |
| Date | Maintenance Schedule |
| Jul 14 2023 | 4 years fee payment window open |
| Jan 14 2024 | 6 months grace period start (w surcharge) |
| Jul 14 2024 | patent expiry (for year 4) |
| Jul 14 2026 | 2 years to revive unintentionally abandoned end. (for year 4) |
| Jul 14 2027 | 8 years fee payment window open |
| Jan 14 2028 | 6 months grace period start (w surcharge) |
| Jul 14 2028 | patent expiry (for year 8) |
| Jul 14 2030 | 2 years to revive unintentionally abandoned end. (for year 8) |
| Jul 14 2031 | 12 years fee payment window open |
| Jan 14 2032 | 6 months grace period start (w surcharge) |
| Jul 14 2032 | patent expiry (for year 12) |
| Jul 14 2034 | 2 years to revive unintentionally abandoned end. (for year 12) |