JP2001158029A - Method for mixing thermoplastic resin and additives by nozzle for injection molding machine, and nozzle body for injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for mixing a thermoplastic resin and additives by a nozzle for an injection molding machine capable of efficiently mixing a gas or a pigment and a thermoplastic resin by a nozzle having a cut-off valve and a radial dispersing mixer and the nozzle for the injection molding machine. SOLUTION: In a method for mixing a thermoplastic resin by a nozzle for an injection molding machine and the nozzle body for the injection molding machine, a nozzle 1 having a dispersing function radially and increasingly diffused from the center thereof to the circumference thereof and a cut-off valve 10 is arranged to the leading end of the injection molding machine to mix a thermoplastic resin and additives melted in the injection molding machine. As the additives, a foaming agent such as carbon dioxide in a supercritical state and a nucleating agent or pigment are used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for mixing a thermoplastic resin and an additive by a nozzle for an injection molding machine and a nozzle body for an injection molding machine, and more particularly to a method using a radial dispersion mixer and a shut-off valve. The present invention relates to a novel improvement for mixing a thermoplastic resin and an additive or a thermoplastic resin with a pigment and the like necessary for producing a foam in a supercritical state.

[0002]

2. Description of the Related Art Conventionally, for example, US Pat.
In No. 986, a thermoplastic resin is melted in a cylinder of an injection molding machine, impregnated with supercritical carbon dioxide, and then rapidly heated when uniformly dispersed to generate cell nuclei to control foaming. A method is disclosed. However, with only the cylinder and screw of the injection molding machine, the mixing of gas and resin is insufficient, so that a static mixer is often attached to the tip of the molding machine.

The static mixer is an in-line mixer having no moving parts, developed by Arthur D. L. of the United States, commercialized by a license from Kenix Corporation, and sold under the trade name Static Mixer. Is widely used.

[0004]

However, the mechanism of this static mixer is basically divided-position-moved-
It consists of superposition and has a bow tie-like element built into the mixer tube. Therefore, in order to obtain a high mixing efficiency, the overall length is increased and the pressure loss is increased.

When the number of elements incorporated in the static mixer is n, the number of divided layers (S) of two liquids is S = 2
given by ⁿ . Therefore, the number of divided layers when the number of elements is 20 is calculated as S = 2 ²⁰ ≒ 1.05 × 10 ⁶ ,
The number of divided layers is about 1.05 million. In addition, when the number of elements is increased in order to improve the mixing performance, the total length of the mixer becomes longer, and a longer heater must be attached. As a result, there is a problem that temperature control and the like are difficult.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and in particular, a thermoplastic resin and an additive or a thermoplastic resin necessary for producing a foam using a radial dispersion mixer and a shutoff valve. It is an object of the present invention to provide a method for mixing a thermoplastic resin and an additive by a nozzle for an injection molding machine in which mixing of a pigment or the like is performed in a supercritical state, and a nozzle body for the injection molding machine.

[0007]

According to the present invention, a method for mixing a thermoplastic resin and an additive by a nozzle for an injection molding machine spreads radially from the center to the circumference toward the tip of the injection molding machine. A method of mixing a thermoplastic resin and an additive melted in an injection molding machine with a dispersing function and installing a nozzle having a shutoff valve, and closing the shutoff valve, wherein the additive is used. A method in which a foaming material such as carbon dioxide gas in a supercritical state and a nucleating agent are used, and the additive is a pigment, and the nozzle body for an injection molding machine according to the present invention is formed by injection molding. In a nozzle body for an injection molding machine having a nozzle attached to the tip of a cylinder of the machine,
The nozzle has a configuration in which a radial dispersion mixer and a shut-off valve are provided, and the radial dispersion mixer is
This is a configuration in which an inner element having a large number of honeycomb-shaped honeycomb chambers and an outer element are joined.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a method for mixing a thermoplastic resin and additives by a nozzle for an injection molding machine and a nozzle for an injection molding machine according to the present invention will be described below with reference to the drawings.

FIG. 1 is a structural view of a nozzle for an injection molding machine having a radial dispersion mixer according to the present invention. As shown in the figure, the mixing method of the thermoplastic resin and the additives according to the present invention comprises attaching a shutoff valve and an arbitrary number of radial dispersion mixers 2 to a nozzle 1 attached to the tip of an injection molding machine, as described below. It is characterized in that a thermoplastic resin melted by an injection molding machine and an additive are mixed. In addition, the nozzle 1 includes:
A known rotary or needle type shut-off valve 10 is provided. When mixing the thermoplastic resin and the additive in the radial dispersion mixer 2, the shut-off valve 10 is closed.

As the radial dispersion mixer 2, a known, for example, Lamond super mixer is used. this is,
A mixer based on a mixing principle based on a dispersion mechanism that proliferates and diffuses radially from the center to the circumference, and is currently used exclusively for mixing water and oil. This mixer 2
One unit is arranged on the proliferation and diffusion side in which the fluid entering from the center radially spreads in the radial direction toward the circumference as shown in FIG. 2, and on the back of the proliferation and diffusion side as shown in FIG. Conversely, it is composed of a pair on the gathering side from the circumference to the center. Each of the diffusion side and the collection side is composed of two elements, the outer elements 3a and 3b are larger than the inner elements 4a and 4b, and the central portion is provided with holes 5a and 5b of a predetermined size. , 4b are not provided with holes. Both elements 3a, 4a (3b, 4
The shape b) is circular and has a structure in which the board surface is covered with a honeycomb chamber group 6 including a large number of honeycomb chambers 6a. This 2
When the elements 3a, 4a (3b, 4b) are overlapped, the honeycomb chamber groups 6 overlap each other with a half-shift, thereby forming a two-layer structure of the radial honeycomb chamber groups 6.
This one set is a half unit, and as shown in FIG. 4, one unit of the mixer 2 is composed of two sets of half units each having a large outer element 3 having holes 5a and 5b.
a, 3b outside, small inner elements 4a, 4
b is back-to-back.

The liquid entering through the hole 5a of the large outer element 3a of the half unit upstream of the mixer 2 is:
The honeycomb chamber group 6 diffuses radially in the radial direction toward the circumference through the two-layer structure of the honeycomb chamber group 6 and passes through the outer peripheries of the small inner elements 4a and 4b of the upstream and downstream half elements. Gathered radially through the two-layer structure of FIG.
Is discharged from. The above diffusion and aggregation mixes fluids with the principle of punching and reversing rice cakes.

Equation 1 shows the number of fluid divisions in the mixer 2.

The number of divisions on the diffusion side of an element having the number of columns N = 3
(2 ^N−1 +2 ^N−2 +2 ^N−4 +2 ^N−6 ...) The number of divisions on the set side of the elements having N columns = 3N × 2 ^{(N−2) −1} fluid number 2,
Number of divided layers Sn = 2 [9N × 2]
^{(N−2) −1} (2 ^N−1 +2 ^N−2 +2 ^N−4 +2 ^N−6 ...)] N If the number of columns is 6 and the number of units is 6 in the above expression of the number of division layers Sn, division is performed. The number of layers is 4.5 × 10 ²⁴ . Note that the number of divided layers can be changed depending on the number of columns. When the number of columns is 6,
The number of divisions per unit is 1.15 × 10 ^4, but the number of columns is 1
At 0, the division number of one unit is 2.46 × 10 ⁶ . That is, when the number of elements of the static mixer is 20 with only one unit having 10 columns, the number of divided layers is 1.
It can exceed 05 × 10 ⁶ .

Therefore, even when a high mixing ratio is obtained, the number of units to be used can be reduced, so that the overall length can be shortened. Also, since the heater size can be shortened, control is easy.
As a result, stable mixing is obtained. If only spacers are incorporated, the mixing unit can be omitted.

Although the mixing performance of the above mixer is theoretically higher than that of the static mixer, there is a concern about the pressure loss in view of the structure. However, by appropriately designing the mixer, the pressure loss can be minimized. FIG. 5 shows the relationship between the firing speed setting and the injection speed of the nozzle and the normal nozzle according to the present invention. In this experimental example, PP and ABS are used as resins,
The nozzle (MIX) according to the present invention and the normal nozzle (SVO) are used as nozzles.

FIG. 6 is a drawing-substituting photograph showing a cross section of a foamed molded article formed by using the mixer according to the present invention and a conventional static mixer, and FIG.
When using a unit mixer, (b)
The case where the static mixer of the element is used is shown. When the mixer according to the present invention is used, FIG.
As shown in (1), a foam molded article having a good surface appearance, a fine uniform cell diameter, and a uniform average cell density can be produced.

FIG. 7 is a photograph substituted for a drawing showing the state of dispersion of the pigment in a molded article molded by using the mixer according to the present invention and a conventional static mixer. In the case where a mixer is used, (b) shows the case where a conventional 6-element static mixer is used. When using the mixer according to the invention, FIG.
As shown in (a), the resin and the pigment can be uniformly dispersed.

[0018]

The method for mixing a thermoplastic resin and an additive using the nozzle for an injection molding machine and the nozzle body for an injection molding machine according to the present invention have the following effects. Can be. That is, the mixing of the supercritical gas and the resin is insufficient in the ordinary static mixer, but in the present invention, the injection molding machine nozzle has a dispersive mechanism that diffuses and diffuses radially from the center to the circumference. The use of a basic mixer and shut-off valve prevents supercritical gas from leaking from the nozzle.The mixing is performed while the flow of thermoplastic resin and additives is stopped. And the pigment and the resin can be efficiently mixed. In addition, there is an advantage that the total length of the mixer can be shortened, control is easy, and stable mixing can be performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a nozzle for an injection molding machine having a radial dispersion mixer according to the present invention.

FIG. 2 is a perspective view of a half unit on the proliferation and diffusion side of a radial dispersion mixer, where (a) shows an outer element and (b) shows an inner element.

FIG. 3 is a perspective view of a half unit on the collecting side of the radial dispersion mixer, where (a) shows an inner element and (b) shows an outer element.

FIG. 4 is a perspective view of a radial dispersion mixer.

FIG. 5 is a diagram showing the relationship between the firing speed setting and the injection speed of the nozzle and the normal nozzle according to the present invention.

FIG. 6 is a photograph substituted for a drawing showing a cross section of a foam molded article molded by using the mixer according to the present invention and a conventional static mixer.

FIG. 7 is a photograph as a substitute of a drawing showing the state of dispersion of pigment in a molded product molded using the mixer according to the present invention and a conventional static mixer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Nozzle 2 Radial dispersion mixer 3a, 3b Outer element 4a, 4b Inner element 5a, 5b Hole 6 Honeycomb chamber group 10 Shut-off valve

Claims (5)

[Claims] 1. A nozzle (1) having a dispersing function of radially proliferating and diffusing radially from a center to a circumference and having a shutoff valve (10) is installed at the tip of an injection molding machine, and said shutoff valve ( 1
A method for mixing a thermoplastic resin and an additive by a nozzle for an injection molding machine, wherein the thermoplastic resin melted by the injection molding machine and the additive are mixed in a state where the valve is closed. 2. The method according to claim 1, wherein the additives are a foaming material such as carbon dioxide in a supercritical state and a nucleating agent.
A method for mixing a thermoplastic resin and an additive with the nozzle for an injection molding machine according to the above. 3. The method for mixing a thermoplastic resin and an additive by using a nozzle for an injection molding machine according to claim 1, wherein the additive is a pigment. 4. A nozzle body for an injection molding machine having a nozzle (1) attached to a tip of a cylinder of the injection molding machine, wherein said nozzle (1) has a radial dispersion mixer (2) and a shut-off valve (10).
A nozzle body for an injection molding machine, wherein a nozzle body is provided. 5. The radial dispersion mixer (2) has an inner element (4a, 4b) having a plurality of honeycomb-shaped honeycomb chambers (6a).
The nozzle body for an injection molding machine according to claim 4, characterized in that the nozzle body (4b) and the outer element (3a, 3b) are joined.