JPH11277664A - Thermoplastic resin foamed body containing wood powder and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide superior mechanical strength such as rigidity and control the expansion ratio. SOLUTION: A wood powder-containing thermoplastic resin foamed body 1 is molded by foam extrusion molding out of molding material composed of thermoplastic resin blended with wood powder, and formed of a solid skin layer 2 on the outer face side, a low-foamed core layer 4 on the axial center side and a foamed layer 3 between the skin layer 2 and the core layer 4. As for the thermoplastic resin, the thermoplastic resin of 250 deg.C melting temperature or lower is used, and the blend ratio of wood powder with the thermoplastic resin is set in the range of 30-80 wt.% to carry out the stabilized foam extrusion molding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic resin foam containing wood flour and a method for producing the same.

[0002]

2. Description of the Related Art An example of a conventional method for producing a thermoplastic resin foam having a wood grain pattern will be described.

As shown in FIG. 4, an extrusion die 10 having a plurality of extrusion holes 102a is sequentially provided from a heating cylinder 101 side.
2. Using a screw-type extruder 110 to which a frame die 103 is attached, a foamable thermoplastic resin containing a brown pigment is plasticized and extruded into a plurality of strips from a plurality of extrusion holes 102a. While passing through the mold 103, it is foamed and fused and focused together, and the guides 108,
After regulating the outer dimensions through the sizing plate 104 and the frame member 105, it is cooled and solidified in a water tank 106 to obtain a thermoplastic foam 107 having a wood grain pattern (Japanese Patent Publication No. 61-1986).
17646).

[0004]

In the above prior art,
Since the plurality of extruded strips are foamed while passing through the frame mold and are fused and focused together, there is a possibility that the fusion of the strips becomes insufficient and molding defects may occur. In addition, the expansion ratio becomes unstable, and the quality of the thermoplastic resin foam varies.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and is made of a thermoplastic resin containing wood flour, which is superior in mechanical strength such as rigidity and can control the expansion ratio. An object is to realize a foam and a method for producing the same.

[0006]

Means for Solving the Problems In order to achieve the above-mentioned object, a thermoplastic resin foam containing wood flour of the present invention is obtained by subjecting a molding material obtained by blending wood flour to a thermoplastic resin to foam extrusion molding. An unfoamed skin layer on the outer surface side, a low foamed core layer on the axial center side, and a foamed layer between the skin layer and the core layer.

The molding material is prepared by blending wood powder within a range of 30 to 80% by weight with a thermoplastic resin having a melting temperature of 250 ° C. or lower.

[0008] Further, the skin layer has a wood grain pattern.

The method for producing a foam made of a thermoplastic resin containing wood powder according to the present invention comprises the steps of kneading and melting a molding raw material obtained by mixing wood powder with a thermoplastic resin by a screw type extruder and extruding it as a cylindrical body; Forming an unfoamed skin layer by cooling and solidifying the outer surface of the extruded tubular body with a sizing die to form an unfoamed skin layer, and foaming toward the axial center of the hollow portion to form a foamed layer; and Cooling and solidifying the cylindrical body on which the foamed layer is formed to form a low-foamed core layer on the axial center side.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an embodiment of a thermoplastic resin foam containing wood flour according to the present invention will be described.

FIG. 1 shows a thermoplastic resin foam containing wood flour according to one embodiment. The thermoplastic resin foam 1 containing wood powder is obtained by foaming a molding material obtained by mixing wood powder with a thermoplastic resin. It is an extruded cylindrical shape, and includes a non-foamed skin layer 2 on the outer surface side, a low-foamed core layer 4 on the axial center side, and a foamed layer 3 between the skin layer 2 and the core layer 4. Become.

As the thermoplastic resin, the melting temperature is 250 ° C.
The following thermoplastic resin is used. The reason is that in the case of a thermoplastic resin having a melting temperature higher than 250 ° C., wood powder mixed with the thermoplastic resin is degraded or carbonized due to thermal decomposition during plasticization, and molding defects occur.

As the wood flour, there can be used pulp and a material mainly composed of cellulose, in addition to crushed products such as wood chips, offcuts and wood chips, sander powder, sawdust and sawdust.

The mixing ratio of the wood powder to the thermoplastic resin is as follows:
When the content is within the range of 30 to 80% by weight, stable foam extrusion can be achieved. When the blending ratio of the wood powder to the thermoplastic resin is less than 30% by weight,
Foaming becomes difficult only by blending wood flour alone. vice versa,
When the mixing ratio of the wood powder to the thermoplastic resin is more than 80% by weight, it is difficult to form an unfoamed skin layer, and the outer surface becomes rough, sharkskin, and cracks. In addition, unless the extrusion speed is extremely low, foam extrusion cannot be performed, resulting in poor productivity.

In the foaming of the present invention, the compounded wood flour expands by heating, and a foam layer is formed by the expansion of the wood flour. For this reason, the present invention is also effective for a thermoplastic resin of a type in which gas by the foaming agent is dissipated in the conventional foaming with the foaming agent. That is, in the present invention, the thermoplastic resin used has a melting temperature of 250.
Any type can be used as long as the temperature is below ° C.

The wood resin-containing thermoplastic resin foam according to the present invention is not limited to the columnar one shown in FIG. 1, but may be an elliptical column, a prismatic column, a polygonal column, or the like, if necessary. Needless to say, these core layers can be changed to hollow cylindrical ones.

Next, one embodiment of a method for producing a thermoplastic resin foam containing wood powder according to the present invention will be described with reference to FIGS.

(1) The heating cylinder 12 of the screw type extruder 11 is heated to a predetermined temperature, and a molding material in which wood powder is mixed with a thermoplastic resin is supplied through a hopper 18 to knead and melt. Then, it is extruded as a tubular body 19 from an annular extrusion hole 14 a of a die 14 attached to the head 13.

The above molding material is processed into granules or pellets by hot mixing an inorganic additive such as talc, titanium oxide, calcium carbonate or the like in an amount necessary for improving the extrudability. Good.

(2) The outer surface of the cylindrical body 19 is cooled and solidified by passing the cylindrical body 19 extruded in the above (1) through the first sizing die 15 cooled to a predetermined temperature by the cooling means 15a. To form an unfoamed skin layer 2 and foam toward the axial center of the hollow portion 19a.

(3) After the above (2), the cylindrical body 19 having the foaming layer 3a being foamed inside the skin layer 2 is passed through the second sizing die 16 so that the outer surface is further regulated and the hollow body is further hollowed. By foaming toward the axial center of the portion 19a, and then cooling and solidifying in the cooling bath 17 to form the low foaming core layer 4 on the axial center side, the thermoplastic resin foam 1 containing wood powder is formed. Get.

In this step, a core layer is formed on the axis portion side, and the core layer contracts in a well-balanced manner as the foaming proceeds toward the axis portion, so that the distribution of the foaming pressure is made uniform. For this reason, a foamed layer with little change in the expansion ratio is formed.

In the present invention, the above-mentioned foaming is carried out by gasification of volatile components such as water and lignin components contained in the wood powder mixed with the thermoplastic resin, and the wood powder expands. The expansion due to the foaming is directed toward the axial center of the hollow portion 19a of the tubular body 19 having the unfoamed skin layer 2 formed on the outer surface.
The expansion ratio can be controlled to a predetermined value by a method such as adjusting the thickness or cooling temperature of the foam.

When a skin layer having a wood grain pattern is formed, it is preferable to use a blend of 0.01 to 30 parts by weight of a pigment master batch with respect to 100 parts by weight of the above-mentioned molding material.

[0025]

EXAMPLE Using a screw-type extruder of L / D22 having the same construction as the screw-type extruder shown in FIGS. 2 and 3, foaming of the above-mentioned thermoplastic resin containing wood powder with the following molding materials and molding conditions. By the same process as the method for producing the body, a columnar thermoplastic resin-containing foam made of wood powder was produced.

The obtained thermoplastic resin foam containing wood flour had a fine grain pattern appearing on the skin layer, and was superior in mechanical strength such as rigidity.

(Molding Material) Using a molding material obtained by mixing 50% by weight of wood powder and 10% by weight of an inorganic additive in an ABS resin, 5 parts by weight of a brown pigment masterbatch was blended with 100 parts by weight of the molding material. thing.

(Molding conditions) Inner diameter of die, first and second sizing dies: 35 mm Initial setting temperature of heating cylinder Supply unit: 150 ° C Compressing unit: 185 ° C Melting unit: 160 ° C Initial setting temperature of die: 120 ° C Initial setting temperature of 1 sizing die: 50 ° C Screw rotation speed: 34 rpm

[0029]

Since the present invention is configured as described above, the following effects can be obtained.

A molding material obtained by blending wood powder with a thermoplastic resin is foamed and extruded. An unfoamed skin layer on the outer surface side, a low-foaming core layer on the axial center side, and a Since it is made of a foamed layer, the foaming ratio can be controlled to have a specific gravity close to that of wood, and a beautiful grain pattern or the like can appear on the surface of the skin layer.

[Brief description of the drawings]

FIG. 1 shows one embodiment of a thermoplastic resin foam containing wood flour according to the present invention, wherein (a) is a schematic perspective view with a part cut away, and (b) is a schematic cross-sectional view.

FIG. 2 is an explanatory view showing one embodiment of a method for producing a thermoplastic resin foam containing wood flour according to the present invention.

FIG. 3 is a schematic partial sectional view taken along line AA of FIG. 2;

FIG. 4 is an explanatory view showing one example of a conventional method for producing a thermoplastic resin foam.

[Explanation of symbols]

 Reference Signs List 1 foam made of thermoplastic resin containing wood powder 2 skin layer 3 foam layer 3a foam layer during foaming 4 core layer 11 screw type extruder 12 heating cylinder 13 head 14 die 14a extrusion hole 15 first sizing die 16 second sizing die 17 Cooling tank 18 Hopper 19 Cylindrical body 19a Hollow part

Continued on the front page (51) Int.Cl. ⁶ Identification code FI // B29K 101: 12 105: 04 105: 16 511: 14 B29L 9:00

Claims (4)

[Claims] 1. A foamed material obtained by blending wood powder with a thermoplastic resin, which is foamed and extruded, comprising: an unfoamed skin layer on an outer surface side; a low foamed core layer on an axial center side; A foam made of a thermoplastic resin containing wood powder, comprising a foam layer between the layer and the core layer. 2. The molding material according to claim 1, wherein the molding material is a mixture of a thermoplastic resin having a melting temperature of 250 ° C. or less and wood flour within a range of 30 to 80% by weight. Thermoplastic foam. 3. The thermoplastic resin foam containing wood flour according to claim 1, wherein the skin layer has a wood grain pattern. 4. A step of kneading and melting a molding raw material in which wood powder is blended with a thermoplastic resin by a screw type extruder and extruding it as a cylindrical body, and cooling and solidifying an outer surface of the extruded cylindrical body by a sizing die. Forming an unfoamed skin layer and foaming toward the axial center of the hollow portion to form a foamed layer; and cooling and solidifying the cylindrical body on which the skin layer and the foamed layer are formed. Forming a low-foaming core layer on the side of the axial center portion.