JP2000037751A - Method for foam injection molding of wood flour- containing thermoplastic resin-made foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a wood grain pattern of a good outward appearance while a mechanical strength of stiffness or the like is improved. SOLUTION: A molding material wherein a wood flour is blended in a thermoplastic resin is fed into a heating cylinder 2 from a hoper 10, plasticized and the molten molding material is measured. When the measurement is completed, after executing a nozzle touch, a screw 3 is advanced, the molten molding materials branched by a torpedo ring 7 having a plurality of through holes 7a for branching the melted molding material and the through holes 7a, are joined, and the molten molding material is cylindrically injected and filled into a cavity 11a of a mold 11 from an injection nozzle 4 having an annular passage 9 for injecting cylindrically, and foamed. Thereby, a molded product comprising an imfoamed skin layer having a wood grain pattern on an outer surface side, a low foamed core layer on a core side, and a foamed layer between the skin layer and the core layer can be foam-injection molded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foam injection molding method for a thermoplastic resin foam containing wood grain having a grain pattern.

[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. 5, 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, an expandable thermoplastic resin containing a brown pigment is plasticized to extrude a plurality of strips from a plurality of extrusion holes 102a. While passing through the mold 103, it is foamed and fused and focused on each other.
8. After the outer dimensions are regulated by passing through the sizing plate 104 and the frame member 105, the thermoplastic foam 107 having a wood grain pattern is foamed and extruded by cooling and solidifying in a water tank 106 (Japanese Patent Publication No. 61-17646). reference).

[0004]

In the above prior art, a plurality of extruded strips are fused together with foaming by passing them through a frame, so that the fusion of the strips is insufficient. This may result in insufficient mechanical strength such as rigidity.

Further, a rod-shaped body whose cross-sectional shape does not change in the axial direction can only be manufactured, and when a cross-sectional shape changes in the axial direction or a bent rod-shaped body is manufactured, secondary processing is performed. Although it is necessary, there is an unsolved problem that the grain pattern is distorted during the secondary processing and the appearance is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned unresolved problems of the prior art, and is intended to be a tree having excellent mechanical strength such as rigidity and having a good-looking grain pattern. An object of the present invention is to realize a foam injection molding method of a thermoplastic resin foam containing wood powder, which can produce a thermoplastic resin foam containing powder.

[0007]

In order to achieve the above object, a foam injection molding method for a thermoplastic resin foam containing wood flour according to the present invention has a plurality of through holes for diverting a molten molding material. Using a screw-type injection device equipped with an injection nozzle having an annular flow path for injecting the molten molding material separated by the torpedo ring and the through hole into a cylindrical shape and injecting the same, wood powder is added to the thermoplastic resin. After plasticizing the compounded molding material and weighing the molten molding material, by injecting and filling the cylindrical molten molding material into a cavity of a mold temperature-controlled to a predetermined temperature, and foaming in the cavity. A foamed injection molding of a molded product comprising an unfoamed skin layer having a wood grain pattern on the outer surface side, a low foamed core layer on the central portion side, and a foamed layer between the skin layer and the core layer. And it is characterized in and.

As the molding material, 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 is used.

[0009]

Embodiments of the present invention will be described with reference to the drawings.

First, a screw type injection molding machine used in the embodiment of the present invention will be described.

As shown in FIG. 1, a screw-type injection molding machine 1 includes a heating cylinder 2 heated by a heating means (not shown), and a screw disposed in the heating cylinder 2 so as to be rotatable and movable in the axial direction. 3 and screw driving means (not shown) for rotating and moving the screw 3 in the axial direction. After plasticizing a molding material, which will be described later, supplied from the hopper 10 and weighing the molten molding material, the tip of the heating cylinder 2 It is configured to be capable of injecting and filling in a cylindrical state into a cavity 11a of a mold 11 clamped from an injection nozzle 4 described later attached to the mold.

The injection nozzle 4 has an inlet-side tubular portion 5 connected to the tip of the heating cylinder 2 and a flange 5a at the tip of the inlet-side tubular portion 5 via a flange 6a at the rear end. An outlet-side tubular portion 6 connected, a torpedo ring 7 provided at a connecting portion between the inlet-side tubular portion 5 and the outlet-side tubular portion 6,
A mandrel 8 is provided concentrically in the outlet side cylindrical portion 6 by fixing one end side to the axial center portion of the torpedo ring 7, and the torpedo ring 7 has a plurality of through holes 7a penetrating in the axial direction. Are provided at intervals in the same direction. For this reason, by moving the screw 3 forward during the injection step, the molten molding material press-fitted from the heating cylinder 2 into the inlet-side tubular portion 5 is divided by the through holes 7a, and then the inner wall surface of the outlet-side tubular portion 6 It merges in an annular flow passage 9 formed between the outer peripheral surface of the mandrel 8 and the outer peripheral surface of the mandrel 6b, and is ejected in a cylindrical state.

FIG. 2 shows an example of a thermoplastic resin foam containing wood flour produced according to the present invention. The L-shaped rod-shaped thermoplastic resin-containing foam 12 containing wood powder has a circular cross-section obtained by foaming and injection-molding a molding material obtained by mixing wood powder with a thermoplastic resin, and has a circular cross-sectional shape. It has an unfoamed skin layer 12a having a wood grain pattern, a low foaming core layer 12c on the axial center side, and a foam layer 12b of the skin layer 12a and the core layer 12c.

In the present invention, the thermoplastic resin includes
A thermoplastic resin having a melting temperature of 250 ° C. or less 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 at the time of plasticization and measurement is deteriorated or carbonized by thermal decomposition, and molding failure occurs. is there.

As the wood flour, there can be used pulp and cellulose-based materials in addition to crushed products such as wood chips, scraps, wood chips and the like, sander powder, sawdust and sawdust.

The mixing ratio of the wood powder to the thermoplastic resin is as follows:
When it is within the range of 30 to 80% by weight, stable foam injection molding can be performed. 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 the foaming of the present invention, the volatile components such as water and lignin contained in the wood powder mixed with the thermoplastic resin are gasified by heating, and the wood powder itself expands. Forms a foam layer. 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, the type of the thermoplastic resin used in the present invention is not limited as long as the melting temperature is 250 ° C. or less.

The steps of the foam injection molding method for the thermoplastic resin foam containing wood powder of the present invention will be described with reference to an example of manufacturing a bent rod-shaped thermoplastic resin foam shown in FIG. .

The heating cylinder 2 is heated to a predetermined temperature, the screw 3 is rotated at a predetermined rotation speed, and a molding material in which wood powder is blended with a thermoplastic resin supplied via a hopper 10 (hereinafter, “molding material”) Is plasticized and the molten molding material is measured.

In this step, if the back pressure applied to the screw 3 is set within the range of 5 to 15 kg / cm ² , stable measurement can be performed. When the back pressure is less than 5 kg / cm ² , insufficient measurement occurs. On the other hand, when the back pressure is more than 15 kg / cm ² , it takes time to measure and the temperature of the heating cylinder 2 rises.

The rotation speed of the screw 3 is 3 to 50 r.
It is preferably set within the range of pm. Screw 3
When the rotation speed is lower than 3 rpm, molding defects such as cracks occur in the molded product. Conversely, when the rotation speed is higher than 50 rpm, the molding material excessively generates heat and the grain pattern does not appear, Burning may occur.

When the above measurement is completed, the nozzle 3 is touched, and then the screw 3 is moved forward, and the molten molding material is injected and filled into the cavity 11 a of the mold 11 which has been clamped in a cylindrical state.

In the present step, the temperature of the mold is preferably adjusted within the range of 90 ° C. to 130 ° C. in accordance with the type of the thermoplastic resin. If the temperature of the mold is lower than 90 ° C., the gloss of the skin layer is impaired, and if it is higher than 130 ° C., cooling time is increased and productivity is deteriorated.

Also, since it is necessary to fill the cavity of the mold with the molten molding material in a cylindrical state, the cross-sectional area of the flow path between the nozzle touch portion and the cavity is as large as possible and the cross-sectional area varies. It is desirable to use a mold having a small diameter.

As the amount of the molten molding material injected and filled into the cavity 11a in a cylindrical state increases, the outer surface thereof contacts the cavity 11a and is cooled and solidified to form a skin layer 12a having a wood grain pattern. Is formed, and the foam layer 1 made of wood powder is moved toward the axial center of the hollow portion.
2b is formed.

After the above, if necessary, the screw 3 is slightly advanced to maintain the pressure, and then cooled in a mold. As the cooling progresses, a low-foaming core layer 12c is formed at the center of the molded product. Is formed, and then the whole is cooled and solidified.

In the present invention, the grain pattern appearing on the skin layer can be changed by devising the sectional shape and arrangement of the plurality of through holes in the torpedo ring.

FIG. 3 shows an example of a torpedo ring.
(A) is a schematic front view, (b) is a schematic side view. The torpedo ring 17 is fixed to a substantially central portion via a head member 19 to which one end of a mandrel 18 is screwed. A plurality of through-holes having a substantially fan-shaped cross section are provided so as to surround the mandrel 18. A hole 17a is provided.

When this torpedo ring 17 is used,
The molten molding material passing through each through hole 17a is
The weld line generated by merging at
A wood grain pattern with mixed grain between straight grains appears.

FIG. 4 shows a modification of the torpedo ring.

The torpedo ring 27 of the first modified example shown in FIG. 4A has a plurality of through holes 27a having a circular cross section so as to surround a mandrel 28. When this torpedo ring 27 is used, a grain pattern in which board grain is mixed between straight grains appears.

In the torpedo ring 37 of the second modification shown in FIG. 4B, a plurality of small through holes 37a having an elliptical cross section are provided so as to surround the mandrel 38, and the outside thereof is further provided. Are provided with a plurality of large through holes 37b having an elliptical cross section. When this torpedo ring 37 is used, a straight grain wood pattern appears.

The torpedo ring 47 of the third modification shown in FIG. 4C has a plurality of circular through holes 47a having a circular cross section so as to surround a mandrel 48. A plurality of small through holes 47b having a substantially elliptical cross section are provided so as to surround the periphery of the hole 47a, and a plurality of large through holes having a substantially elliptical cross section are provided so as to surround the periphery thereof. 47c is provided. When the torpedo ring 47 is used, a straight grain wood pattern appears.

[0034]

[Example] Screw diameter 46 mm, mold clamping force 150 ton,
An injection nozzle having a torpedo similar to the torpedo shown in FIG. 3 was attached to an L / D20 screw-type injection molding machine (J150E-C3 manufactured by Nippon Steel Works Ltd.), and an L nozzle similar to that shown in FIG. A thermoplastic resin foam containing wood powder (outside diameter 35 mm, long side 170 mm, short side 150 mm) bent into a round bar shape was injection foamed under the following molding materials and molding conditions.

The obtained L-shaped bent round bar-shaped thermoplastic resin-containing foam made of thermoplastic resin has a wood grain pattern in which a grain pattern is intermingled between straight grains in the skin layer, and has a rigidity and the like. Was superior in mechanical strength.

(Molding Material) A molding material obtained by blending 50% by weight of wood powder and 10% by weight of an inorganic additive in an ABS resin, and blending 5 parts by weight of a brown pigment master batch with 100 parts by weight of the molding material .

(Molding conditions) Initial setting temperature of heating cylinder Supply unit: 140 ° C Compressing unit: 160 ° C Melting unit: 150 ° C Initial setting temperature of injection nozzle: 160 ° C Initial setting temperature of mold: 100 ° C Screw for measuring Rotation speed: 20 rpm Screw back pressure: 15 kg / cm ² Injection pressure (maximum): 110 kg / cm ² Holding pressure: 42 kg / cm ² Cooling time: 200 seconds Cooling temperature: Room temperature after injection

[0038]

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

A thermoplastic resin-containing molded article having a specific gravity close to that of a wood in which a beautiful grain pattern appears on the skin layer can be injection-molded with high precision.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a screw type injection molding machine used for carrying out the present invention.

FIG. 2 shows an example of a bent round bar-shaped thermoplastic resin-containing foam made of wood powder, which is foamed and injection-molded according to the present invention;
(A) is a schematic plan view, (b) is a schematic side view, and (c) is a schematic enlarged sectional view along line AA of (a).

3A and 3B show an example of a torpedo ring used for carrying out the present invention, wherein FIG. 3A is a schematic front view, and FIG. 3B is a schematic side view.

4A and 4B show a modified example of a torpedo ring used in the embodiment of the present invention, wherein FIG. 4A is a schematic front view of a torpedo ring of a first modified example, FIG. 4B is a schematic front view of a torpedo ring of a second modified example, (C) is a schematic front view of the torpedo ring of the third modified example.

FIG. 5 is an explanatory view showing one example of a conventional method for producing a thermoplastic resin foam.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Screw type injection molding machine 2 Heating cylinder 3 Screw 4 Injection nozzle 5 Inlet side cylindrical part 5a, 6a Flange part 6 Outlet side cylindrical part 7, 17, 27, 37, 47 Torpedo ring 7a, 17a, 27a, 37a, 37b, 47a, 47
b, 47c Through holes 8, 18, 28, 38, 48
Mandrel 9 Annular flow path 10 Hopper 11 Mold 11a Cavity 12 Thermoplastic resin foam containing wood powder with bent rod 12a Skin layer 12b Foam layer 12c Core layer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29K 105: 04 511: 14 (72) Inventor Hironobu Uyama 6-3-12 Higashiyama Honshinmachi, Yao-shi, Osaka F-term (Reference) 4F206 AB11 AB19 AF08 AG20 AR06 JA04 JB30 JD01 JF01 JF02 JQ44 JQ54 JQ57 4F212 AB11 AB19 AF08 AG20 AR06 UA01 UB30 UF01 UN27

Claims (2)

[Claims] 1. A torpedo ring having a plurality of through holes for diverting a molten molding material, and an annular flow path for merging the molten molding material diverted by the through holes into a cylindrical shape for injection. Using a screw-type injection device equipped with an injection nozzle, plasticize the molding material in which wood powder is mixed with a thermoplastic resin, weigh the molten molding material, and then place the cylinder into a mold cavity temperature-controlled to a predetermined temperature. Inject the molten molding material of
By filling and foaming in the cavity, an unfoamed skin layer having a wood grain pattern on the outer surface side, a low foaming core layer on the center side, and a foamed layer between the skin layer and the core layer A foam injection molding method of a thermoplastic resin foam containing wood flour, characterized by subjecting a molded article to foam injection molding. 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. A foam injection molding method for a thermoplastic resin foam.