JP6424681B2 - Method for producing foamed resin molding pellets - Google Patents

Description

The present invention relates to a method for producing a foamed resin molding pellet .

  An electric wire using a fluorine resin as an insulator (so-called fluorine resin electric wire) has a high melting point and is excellent in solder heat resistance, so it is used for solder connection between a cable and a terminal or connector. Moreover, since a fluorine resin wire is excellent in durability against environmental deterioration such as chemical resistance, it is used for internal wiring of electronic devices such as computers and wiring of high frequency devices such as mobile phones and measuring devices. Furthermore, since a fluorine resin electric wire is excellent in heat resistance and cold resistance, it is used as a wire for high temperature devices and a lead wire in a low temperature environment.

  Conventional fluororesin wires use polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkylvinylether copolymer (PFA) or tetrafluoroethylene / hexafluoropropylene copolymer (FEP) as the insulator material. It is done. They are excellent in heat resistance, cold resistance and chemical resistance, and the dielectric constant is also very low at 2.0 to 2.1.

  However, with the recent increase in speed of electronic devices (transmission speed: 10 Gbps / second or more) and high frequency of communication devices (GHz band), it is necessary to further lower the dielectric constant. Therefore, the dielectric constant is lowered by fibrillating the fluorocarbon resin composition by foaming or drawing to achieve porosity.

  The porosification is mainly performed with PTFE. For example, the dielectric constant is reduced by winding tape-shaped PTFE that has been made porous by drawing as an insulator around the outer periphery of the inner conductor (see Patent Document 1). Porous PTFE tapes are mainly used for small diameter high speed transmission cables.

  However, the characteristics deteriorate because the adhesion to the inner conductor is deteriorated. In addition, since the PTFE tape is wound in multiple layers to increase the thickness of the insulating layer, the production speed is reduced accordingly, resulting in high cost.

  In addition, since PTFE can not be melt-extruded, it is impregnated with a solvent such as solvent naphtha into PTFE powder to form a paste, which is then coated on an inner conductor using a paste extruder, and then the solvent is removed in a firing furnace. There is a method of manufacturing an insulated wire by vaporizing and sintering PTFE. Paste insulation foam insulation is mainly used for high frequency coaxial cables.

  As a method of using a paste extruder, for example, there is a method of producing a foam-insulated electric wire by kneading a pore forming agent such as dicarboxylic acid together with PTFE powder and vaporizing the pore forming agent at the time of sintering. (See Patent Document 2).

  However, foaming by a pore forming agent has a problem that the degree of foaming is low and it can not be used for a low loss cable.

  On the other hand, in the case of melt extrudable PFA or FEP, during extrusion, an inert gas such as fluorocarbon gas, nitrogen gas, carbon dioxide gas or the like is injected into the cylinder of the extruder as a foaming agent to discharge the material. The physical foaming system made to foam using the pressure difference of is used (refer patent document 3).

  However, when the physical foaming system is used, it is difficult to control the amount of gas used as the foaming agent, and as a result, the size of the air bubble can not be controlled. In the case of a small diameter foam insulated wire, when the air bubble becomes too large, the outer diameter fluctuation becomes large, which causes a problem of deterioration of the capacitance and the characteristic impedance. In addition, in a large diameter coaxial cable, a large air bubble (鬆) is generated between the inner conductor and the foam insulator along with the outer diameter abnormality, and the voltage standing wave ratio (VSWR), which is an indicator of the cable length direction, The problem of worsening arises.

  Furthermore, a chemical foaming method is also used in which a chemical blowing agent that is foamed by heating at the time of melt extrusion is added to the resin compound to cause foaming.

Chemical blowing agents are roughly classified into two types, inorganic and organic.
The main components of inorganic chemical blowing agents are sodium bicarbonate and the like, which generate carbon dioxide gas having high solubility in the polymer upon decomposition. However, since metal salts having large dielectric constants (ε) and dielectric loss tangents (tan δ) are generated as decomposition products, it is difficult to use for high-speed transmission cables and high-frequency cables that are required to lower the dielectric constant. Therefore, an organic chemical blowing agent is mainly used.

  Examples of organic chemical foaming agents include bistetrazole compounds such as bistetrazole diammonium, bistetrazole piperazine, and bistetrazole diaguanidine. There are a master batch (MB) method and a full compound (FC) method as a method of manufacturing a foaming insulator using an organic type chemical blowing agent. In the MB method, in order to improve the dispersibility of the organic chemical foaming agent, a foaming agent master batch (MB) is prepared by concentrating the chemical foaming agent in the resin to a concentration about 10 times the amount used, and this is used as the base resin Dilute to volume to form a resin foam. On the other hand, in the FC method, the chemical foaming agent and the entire amount of resin are simultaneously kneaded to prepare a foamable compound, which is supplied to a molding machine to mold a resin foam.

  However, among the fluorine resins used for the above-described insulator material, the melting point of FEP is approximately 270 ° C., and the melting point of PFA is approximately 310 ° C. Therefore, the extrusion temperature during melt extrusion is 300 ° C. for FEP and 330 ° C. for PFA. On the other hand, the decomposition temperature of azodicarbonamide (ADCA), which is the azo compound most commonly used as a chemical foaming agent, is 200 ° C., and the decomposition initiation temperature of the tetrazole chemical foaming agent having the highest decomposition temperature is 300 ° C. or less. Therefore, there is a problem that neither the MB method nor the FC method can be applied to the melt extrusion of PFA or FEP because the chemical blowing agent is decomposed by the kneading with the fluorine resin.

  As a method for solving the above problem, there is a method described in Patent Document 4. According to Patent Document 4, a powdery fluorine resin such as PFA or FEP and a powdery chemical foaming agent are mixed without heating and melting, and the solidified and molded pellets are obtained by kneading and foaming by extrusion molding. Disclosed is a foam insulated wire / cable having an insulating layer made of a foamed resin molding.

Japanese Utility Model Application Publication No. 2-34735 JP, 2011-76860, A Patent No. 4879613 JP, 2014-58625, A

  When the pellet is charged into the extruder, the temperature of the cylinder and screw of the extruder is set to a temperature higher than the decomposition temperature of the chemical blowing agent because the fluorocarbon resin is a high melting point resin. Therefore, a part of the chemical blowing agent is decomposed before the molten resin fills in the extruder, and the decomposed gas is volatilized (released to the outside) from the pellet inlet, so the amount of gas dissolved in the molten resin is reduced. In the resin molded product, a sufficient degree of foaming may not be obtained efficiently. The same applies to the case of using other high melting point resins having a melting point higher than the decomposition temperature of the chemical blowing agent as well as the fluorine resin.

Therefore, an object of the present invention is to provide a method for producing a foamed resin molding pellet capable of efficiently utilizing the decomposition gas of the chemical blowing agent when using a high melting point resin having a melting point higher than the decomposition temperature of the chemical blowing agent. It is to do.

In order to achieve the above object, the present invention provides the following method for producing a foamed resin molding pellet .

A method for producing a pellet for molding a foamed resin, comprising: an inner layer containing a high melting point resin and a chemical blowing agent; and an outer layer covering the inner layer and containing a high melting point resin having a melting point higher than the decomposition temperature of the chemical blowing agent. And
Charging the powder of the high melting point resin for the outer layer into a first hopper of a tableting machine;
Charging the material for the inner layer formed into a pellet by mixing the powder of the high melting point resin and the powder of the chemical foaming agent into a second hopper of the tableting machine;
A first weighing step of weighing the powder of the high melting point resin in the first hopper into a die;
Feeding the inner layer material in the second hopper onto the powder of the high melting point resin in the die;
A second weighing step of weighing the powder of the high melting point resin in the first hopper into the die so as to cover the material for the inner layer in the die;
A pressing step of pressing and pelletizing the raw material for the inner layer and the powder of the high melting point resin in the die with an upper and lower crucible;
The manufacturing method of the pellet for foamed resin molding provided with this.

  According to the present invention, the pellet, the foamed resin molded article, the foamed insulated wire and the cable which can efficiently use the decomposition gas of the chemical blowing agent when the high melting point resin having a melting point higher than the decomposition temperature of the chemical blowing agent is used. Can be provided.

It is a sectional view of a pellet concerning an embodiment of the invention. It is the schematic for demonstrating the preparation processes of the inner layer of the pellet which concerns on embodiment of this invention. It is the schematic for demonstrating the preparation processes of the inner layer of the pellet which concerns on embodiment of this invention. It is the schematic for demonstrating the preparation process of the pellet which concerns on embodiment of this invention. It is the schematic for demonstrating the preparation process of the pellet which concerns on embodiment of this invention. It is the schematic for demonstrating the manufacturing process of the foamed resin molded object which concerns on embodiment of this invention. It is the schematic for demonstrating the manufacturing process of the foamed resin molded object which concerns on embodiment of this invention. It is sectional drawing which shows the cross-section of the foam insulated wire which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the cross-section of the foam insulated wire which concerns on the modification of FIG. FIG. 1 is a longitudinal side view of a coaxial cable according to a first embodiment of the present invention. It is sectional drawing which shows the cross-section of the foam insulated wire which concerns on the 2nd Embodiment of this invention. It is a side view of the longitudinal direction of the coaxial cable concerning a 2nd embodiment of the present invention. It is a side view of the longitudinal direction of the coaxial cable concerning the modification of FIG. It is sectional drawing which shows the cross-section of the cable concerning the 3rd Embodiment of this invention. It is sectional drawing which shows the cross-section of the cable concerning the modification of FIG. It is sectional drawing which shows the cross-section of the foam insulated wire which concerns on the 4th Embodiment of this invention. It is sectional drawing which shows the cross-section of the foam insulated wire which concerns on the modification of FIG. It is sectional drawing which shows the cross-section of the foam insulated wire which concerns on the 5th Embodiment of this invention. It is sectional drawing which shows the cross-section of the foam insulated wire which concerns on the modification of FIG.

〔pellet〕
FIG. 1 is a cross-sectional view of a pellet according to an embodiment of the present invention.
The pellet 90d according to the embodiment of the present invention includes an inner layer 90b containing a chemical blowing agent, and an outer layer 90D covering the inner layer 90b and containing a high melting point resin having a melting point higher than the decomposition temperature of the chemical blowing agent. Prepare.

  Here, a pellet means what was solidified and shape | molded in the predetermined shape. The shape is not particularly limited, but various shapes such as a cylindrical shape, a spherical shape, a polygonal prism shape, and an annular shape can be adopted. Particularly preferred is a tablet-like shape of the pharmaceutical.

  As the pellet 90d, the inner layer 90b is formed by solidifying a powder containing a powdery chemical foaming agent without heating and melting, and the outer layer 90D is formed without heating and melting a powder containing a powdery high melting point resin. What was solidified and formed can be used suitably.

  The inner layer 90b may be composed of only a chemical foaming agent, but preferably contains the high melting point resin, and more preferably contains the same high melting point resin as the high melting point resin constituting the outer layer 90D. The inner layer 90b may be composed of only the high melting point resin and the chemical foaming agent, but may contain a foaming nucleating agent and the like described later. In the inner layer 90b of the pellet, the chemical blowing agent is almost uniformly dispersed in the high melting point resin, and the chemical blowing agent is not thermally decomposed. A foam molding is obtained.

  The outer layer 90D may be composed of only the above-mentioned high melting point resin, but may contain a foam nucleating agent and the like described later.

(Chemical blowing agent)
In the embodiment of the present invention, since only a mixture of powders is compacted and pelletized by a tableting machine or the like without heating, any chemical foaming agent can be used regardless of the decomposition temperature.

  The chemical blowing agent used in the embodiment of the present invention is preferably an organic chemical blowing agent. The organic chemical foaming agent is preferably one or more selected from azo compounds, hydrazide compounds, nitroso compounds, semicarbazide compounds, hydrazo compounds, tetrazole compounds, triazine compounds, ester compounds, hydrazone compounds, and diazinon compounds. More preferably, it is at least one selected from an azo compound, a hydrazide compound and a tetrazole compound.

  More specifically, examples of the azo compound include azodicarbonamide (ADCA), azobisisobutyronitrile (AIBN), and barium azodicarboxylate (Ba-ADC). Examples of hydrazide compounds include 4,4'-oxybisbenzenesulfonyl hydrazide (OBSH) and p-toluenesulfonyl hydrazide. Examples of the nitroso compound include dinitrosopentamethylenetetramine (DPT). Examples of semicarbazide compounds include p-toluenesulfonyl semicarbazide (TSSC). As a hydrazo compound, hydrazodicarbonamide (HDCA) is mentioned, for example. Examples of the tetrazole compound include bistetrazole diammonium, bistetrazole piperazine, bistetrazole diguanidine, 5-phenyltetrazole, azobistetrazole guanidine, and azobistetrazole diaminoguanidine. As a triazine compound, a trihydrazino triazine (THT) is mentioned, for example. Examples of the ester compound include hydrazocarboxylic acid ester (HDC-ESTER), azodicarboxylic acid ester (ADC-ESTER), and citric acid ester. As a hydrazone compound, a sulfonyl hydrazide is mentioned, for example. Examples of the diazinon compounds include 5-phenyl-3,6-dihydro-1,3,4-oxadiazin-2-one. Two or more of these may be used in combination.

  The chemical blowing agent is preferably added to the pellets in an amount of 0.1 to 3% by mass with respect to the total amount of the foamed resin molding to be formed. More preferably, it is 0.3 to 3% by mass, and still more preferably 0.5 to 2% by mass. The amount of chemical blowing agent added is the amount required to obtain the desired degree of foaming from the amount of gas generated upon decomposition of the chemical blowing agent and the amount of resin discharged from the extruder. If the content of the chemical blowing agent is within the above range, the influence of the decomposition residue of the chemical blowing agent is small, so that a foamed resin molded article having good electric characteristics of the electric wire can be obtained. In addition, a foamed resin molded article having a small variation in cell diameter can be obtained.

(High melting point resin)
The high melting point resin suitable in the embodiment of the present invention is, for example, one or more selected from fluorine resin, polyamide, polyether ketone and polyether ether ketone. Fluorine resin is particularly preferred. Other super engineering plastics or engineering plastics can also be used. For example, polyphenylene sulfide (PPS), polyether imide (PEI), polybutylene terephthalate (PBT) can be mentioned.

  A resin having a melting point of 240 ° C. or more is preferable, a resin having a melting point of 260 ° C. or more is more preferable, and a resin having a melting point of 300 ° C. or more is more preferable as the effects of the present invention appear more remarkably.

  The high melting point resin is preferably added to the pellet so as to be contained in an amount of 97 to 99.9% by mass in the foamed resin molded body when extrusion molding is performed in a full compound system. More preferably, it is 97 to 99.7% by mass, and still more preferably 98 to 99.5% by mass.

  As the fluorine resin, it is preferable to use one or more selected from tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) and tetrafluoroethylene / hexafluoropropylene copolymer (FEP). Although these may be used together, it is preferable to use PFA and FEP independently, respectively. The melting point of PFA is around 300-315 <0> C, and the melting point of FEP is around 260-270 <0> C.

  In addition to PFA and FEP, ethylene-tetrafluoroethylene-hexafluoropropylene copolymer (EFEP) or ethylene-tetrafluoroethylene copolymer (ETFE), which have relatively low melting points, can also be used.

  As the polyamide, it is preferable to use one or more selected from nylon 6, nylon 66, and nylon 610. Although these may be used in combination, it is preferable to use nylon 6 or nylon 66 alone. The melting point of nylon 6 is approximately 225 ° C, and the melting point of nylon 66 is approximately 265 ° C.

  The high melting point resin used as the material of the pellets is most preferably powdery, but granular ones can also be used. In addition, commercially available pelletized fluorocarbon resin can also be used as a raw material after being broken into powder or granular form.

The size of the pellet is not particularly limited as long as it can be fed into the extruder, but for example, in the case of a cylindrical shape shown in FIG. 1, the diameter (W ₂ ) is about _{2 to 10} mm, the height (H ₂ ) The size is preferably about _{2 to 10} mm. In this case, the inner layer 90b preferably has a diameter (W ₁ ) of about ₁ to 7 mm and a height (H ₁ ) of about ₁ to 7 mm. More specifically, for example, the diameter (W ₁ ) of the cylindrical inner layer 90 b is 2 mm, the height (H ₁ ) is 1.5 mm, the diameter of the pellet 90 d (W ₂ ) is 3 mm, the height (H) ₂ ) = 2.5 mm. It is preferable that the inner layer 90b be entirely covered with the outer layer 90D and disposed at the center of the pellet 90d.

  The volume ratio of the inner layer 90b to the outer layer 90D (inner layer: outer layer) is preferably 1: 1 to 1: 5, and more preferably 1: 2 to 1: 4.

  The method for forming pellets is preferably compression molding, and compression molding can be performed using a tableting machine or the like for forming tablets of pharmaceuticals and the like. When forming the pellets, polytetrafluoroethylene (PTFE), a wax or the like may be added as a binder.

  By pelletizing, the pellets are uniformly fed to the screw in the extruder, and the resin pressure in the extruder is uniformly applied to the chemical blowing agent, so that the decomposition gas of the chemical blowing agent is uniform in the molten fluorocarbon resin. It can be dispersed and dissolved in water. If the mixed powder is introduced into the extruder as it is without being pelletized, it will not be uniformly fed by the screw, causing variations in resin pressure. In the case of extrusion foaming, it is necessary to dissolve the molten resin and the foaming agent (decomposed gas) in the cylinder of the extruder under high resin pressure, so once the resin pressure in the cylinder fluctuates, it is once dissolved in the molten resin A phenomenon occurs in which the gas is separated due to supersaturation, and it is not possible to produce a uniform foamed electric wire.

(Other ingredients)
The pellet used in the embodiment of the present invention may further contain a foam nucleating agent in the inner layer and / or the outer layer. By using the foaming nucleating agent in combination, the diameter of the generated cells can be made finer. As the foaming nucleating agent, one which does not decompose in the molten fluorocarbon resin and which has good dispersibility can be used. For example, boron nitride, talc, zeolite, silica, activated carbon, silica gel and the like can be suitably used. The foaming nucleating agent may be added to a base resin described later. Alternatively, pellets containing a foam nucleating agent may be prepared separately.

  The pellet used in the embodiment of the present invention is an antioxidant, a lubricant, a copper inhibitor, a flame retardant, a flame retardant auxiliary, a colorant, a filler, a light stabilizer, which is usually blended in the insulating layer of the insulated wire. And a crosslinking agent may be further added. These may be added to the base resin described later.

[Foam resin molding]
The foamed resin molded article according to the embodiment of the present invention is a foamed resin molded article obtained by kneading and foaming the above-mentioned pellets according to the embodiment of the present invention by extrusion molding. In the foamed resin molded product according to the embodiment of the present invention, when the pellet according to the embodiment of the present invention is a master batch, the pellet is a base containing the high melting point resin contained in the pellet. Together with the resin of the present invention, the mixture is extruded by extrusion molding, and the foamed resin molded product is obtained by foaming.

(Master Badge)
The foamed resin molded product according to the embodiment of the present invention can be produced not only by the full compound method but also by extrusion molding by the master batch method. In this case, the aforementioned pellets are preferably used as a masterbatch. The content of the chemical blowing agent in the pellets as a masterbatch is preferably 1 to 30% by mass, more preferably 5 to 20% by mass, and more preferably about 10% by mass with respect to the total amount of the masterbatch. It is more preferable to do. The pellet as a master batch is knead | mixed by extrusion molding with resin of the base containing 1 or more types of high melting point resin mentioned later. In this case, extrusion can be carried out by dry blending pellets as a masterbatch and pellets of a high melting point resin as a base resin at the time of extrusion molding.

(Base resin)
In the embodiment of the present invention, as the base resin used in extrusion molding in the master batch method, the same high melting point resin as that contained in the above-mentioned pellets can be used. In particular, it is preferable to use a fluorocarbon resin, in particular PFA and / or FEP.

  The base resin is also preferably used for extrusion in the form of pellets. The shape and size of the pellets are the same as in the case of the pellets containing the chemical blowing agent described above. Commercially available pelletized PFA and / or FEP can be suitably used.

(Characteristics, shape, and application of foamed resin moldings)
The obtained foamed resin molded product contains decomposition residues of the chemical blowing agent. It is preferable to remove removable decomposition residues. As an example of decomposition residues, decomposition residues of azo compounds such as cyanuric acid, urazole, biurea, decomposition residues of hydrazide compounds such as polydithiophenyl ether, polythiophenyl benzene sulfonyl ether, decomposition residues of nitroso compounds Examples of the decomposition residue of hexamethylenetetramine and hydrazo compounds include, for example, urazole.

  In a preferred embodiment of the present invention, the foamed resin molded product has an average cell diameter (equivalent circle diameter) of 200 μm or less. The average cell diameter (equivalent circle diameter) in the case of using the foamed resin molded product as the insulator of the small diameter insulated wire is 100 μm or less, preferably 65 μm or less. When using a foamed resin molded product as an insulator of a large diameter insulated wire, the average cell diameter (equivalent circle diameter) is 200 μm or less, preferably 160 μm or less.

  In a preferred embodiment of the present invention, the foamed resin molded product has a degree of foaming of 30% or more. The degree of foaming in a more preferred embodiment is 35% or more, and the degree of foaming in a further preferred embodiment is 40% or more.

  In a preferred embodiment of the present invention, the foamed resin molded product has a characteristic impedance of 48 to 52 Ω.

  In a preferred embodiment of the present invention, the foamed resin molded article is excellent in properties such as solder heat resistance, deformation rate, drawing force, voltage standing wave ratio and the like.

  The foamed resin molded product according to the embodiment of the present invention can have various shapes, for example, can have a string shape, a plate shape, a film shape, or a pipe shape.

  The foamed resin molded product according to the embodiment of the present invention can be suitably used for the insulating layer of the insulated wire and the cable. For example, it can also be suitably used as an insulating layer of a differential signal transmission cable capable of high-speed transmission of 10 Gbps class or more. In addition, it can be suitably used as an insulating layer of a thin-walled thin coaxial cable for medical use such as a probe cable for ultrasonic diagnosis.

[Method for producing pellet and foamed resin molded article]
The method for producing a foamed resin molded article according to an embodiment of the present invention includes the steps of producing the above-mentioned pellet according to an embodiment of the present invention, and kneading and foaming the pellet by extrusion molding.

  The process of producing the pellet according to the embodiment of the present invention will be described below by taking a method of compression molding using a tableting machine as an example.

(Preparation of inner layer 90b of pellet)
FIGS. 2A and 2B are schematic diagrams for explaining a process of producing the inner layer 90b of the pellet according to the embodiment of the present invention. FIG. 2A is a schematic view from above of a tableting machine for molding the inner layer 90b of the pellets, and FIG. 2B illustrates the tableting process in the positions (1) to (5) shown in FIG. 2A. It is a figure for.

  First, a raw material 90a to be charged into the hopper 91 of the tablet press 90 is prepared. After weighing the powder of the high melting point resin, the powder of the chemical blowing agent, and the other additives as needed, the raw material 90a is obtained by thoroughly mixing them using a mixing apparatus. The mixing apparatus may be charged all at once, or the powder of the high melting point resin and the powder of the chemical blowing agent may be mixed first, and then other additives may be added and further mixed. As a mixing apparatus, general mixing mixers for powder such as tumbler mixers, Henschel mixers and shakers can be used.

  When extrusion is carried out in the full compound system, all the powder of the high melting point resin, the powder of the chemical foaming agent, and other additives are mixed and pelletized by a tableting machine. On the other hand, in the case of extrusion molding in the master batch method, powder of high melting point resin for pellets as a master batch having a high concentration of chemical foaming agent, powder of chemical foaming agent, and other additives are mixed and While pelletizing with a tablet machine, the powder of high melting point resin as a base resin and other additives as needed are mixed and pelletized with a tableting machine.

  As a tableting method, there are a direct tableting method in which the mixed powder is directly compressed and a granular tableting method in which the mixed powder is granulated and then compressed, but in the embodiment of the present invention, either method is also suitable. It can be used.

In the tableting process, (1) a weighing process of weighing the raw material 90a in the hopper 91 into a die 93, and (2) a primary pressurization in which the raw material 90a is primarily pressurized at a low pressure by the upper and lower punches 94 and 95. Step (3) Secondary pressing step (X ₁ and X ₂ indicate the pressing direction) in which the raw material 90a is subjected to secondary pressing at several tens of MPa with the upper and lower punches 94 and 95 and molded (4 ) Ejecting the pellet 90b from the die 93 by the scraper 96 and discharging it out of the tableting machine 90 along the slider 97 (Y ₁ indicates the pellet extraction direction and Y ₂ indicates the pellet ejection direction), (5) It consists of five steps of the cleaning process of cleaning the inside of the die 93. (1) to (5) correspond to (1) to (5) shown in FIGS. 2A and 2B, respectively. A tableting operation can be carried out continuously by arranging and rotating three sets to 15 sets circumferentially by combining these five steps into one set. As a result, pellets of 100,000 particles / hr or more (10 kg / hr or more in weight conversion) can be produced in terms of the number of pellets.

  In the tableting process, it is necessary to optimize the tableting pressure and the tableting speed (rotation speed of the tableting machine). If the tableting pressure is too high, the pellets may be broken or it may be too hard and the load on the extruder motor of the extruder may become too large and the extruder may stop due to abnormal load. . On the other hand, if the tableting pressure is too low, the strength of the pellet is weak, and when it is inserted into the extrusion molding machine, it may be broken and it may not be possible to feed with a screw. For example, in the case of using a raw material 90a composed of a powder of a high melting point resin and a powder of a chemical foaming agent, it is preferable to set a tableting pressure to 30 to 40 kPa and a tableting speed (rotation speed) to 50 to 60 rpm.

(Preparation of Pellet 90d: Coating of Outer Layer 90D)
FIG. 3A and FIG. 3B are schematic diagrams for explaining a production process of a pellet 90d according to the embodiment of the present invention. FIG. 3A is a schematic view from above of a tableting machine for molding pellets 90d, and FIG. 3B is for explaining the tableting process in the positions (1) to (7) shown in FIG. 3A. FIG.

Next, the process of coating the periphery of the produced inner layer 90b with the outer layer 90D will be described.
First, a raw material 90c to be charged into the hopper 91 of the tablet press 900 is prepared. After weighing the powder of the high melting point resin and other additives as needed, the raw material 90c is obtained by thoroughly mixing them using a mixing apparatus. As a mixing apparatus, general mixing mixers for powder such as tumbler mixers, Henschel mixers and shakers can be used.

  In the case of extrusion in a full compound system, the raw material 90c is supplied around the inner layer 90b and pelletized by a tableting machine to obtain pellets 90d. On the other hand, when extruding in the master batch method, the raw material 90c is supplied around the inner layer 90b for pellets as a master batch having a high concentration of chemical foaming agent, and pelletized by a tableting machine to obtain pellets 90d. At the same time, the powder of the high melting point resin as a base resin and other additives as needed are mixed, and pelletized by a tableting machine to produce a pellet 90e shown in FIG.

  The tableting method may be the above-mentioned direct tableting method or granular tableting method.

The tableting process is (1) a primary weighing process of weighing the raw material 90c in the hopper 91 into the die 93, (2) a pellet (inner layer) 90b in the hopper 91A along the slider 98 and the raw material 90c in the die 93 (3) secondary weighing process of weighing the raw material 90c in the hopper 91 into the die 93, (4) primary addition of the raw material 90c at a low pressure by the upper crucible 94 and the lower crucible 95 (5) The secondary pressing step (X ₁ and X ₂ indicate the pressing direction) in which the raw material 90c is subjected to secondary pressing at several tens of MPa with the upper and lower punches 94 and 95 and molded. (6) Ejecting process of extracting the pellet 90d from the die 93 by the scraper 96 and discharging it out of the tableting machine 900 along the slider 97 (Y ₁ indicates the pellet extraction direction and Y ₂ indicates the pellet ejection direction ), (7) A cleaner that cleans the inside of the die 93 Consisting of 7 steps. (1) to (7) correspond to (1) to (7) shown in FIGS. 3A and 3B, respectively. A tableting operation can be performed continuously by arranging and rotating three sets to 15 sets in a circumferential shape by combining these seven steps into one set.

  In the tableting process, it is necessary to optimize the tableting pressure and the tableting speed (rotation speed of the tableting machine). If the tableting pressure is too high, the pellets may be broken or it may be too hard and the load on the extruder motor of the extruder may become too large and the extruder may stop due to abnormal load. . On the other hand, if the tableting pressure is too low, the strength of the pellet is weak, and when it is inserted into the extrusion molding machine, it may be broken and it may not be possible to feed with a screw. For example, when the raw material 90c which consists of powder of high melting point resin is used, it is suitable for a tableting pressure to be 30-40 kPa, and to set tableting speed (rotation speed) to 50-60 rpm.

  Pellets 90d compressed under optimum conditions can be fed at the screw feed of the extruder. Furthermore, the high melting point resin is sufficiently melted in the compression section of the screw, and the gas generated by the decomposition of the chemical blowing agent is sufficiently kneaded with the molten resin, and the gas can be dissolved in the resin.

More specifically, for example, it can be manufactured under the following conditions.
(1) Mixing of high melting point resin and powder of chemical blowing agent
Use kawata super mixer piccolo <working conditions>
Powder amount: 500 g
Agitation upper blade: SI type stirring blade rotation speed: 300 rpm
Stirring lower blade: SL type stirring time: 10 minutes (2) Preparation of pellet 90b Tableting pressure: 0.5 KN to 3 KN
Filling height: 7.5 mm, diameter of mill: φ 2.0 mm
Finished pellet: φ 2.0, height 3.0 mm
Tableting machine rotation speed: 15 rpm
(3) Production of pellet 90d (coating of outer layer 90D)
Tableting pressure: 0.5 KN to 3 KN
Filling height: 7.5 mm, diameter of mill: φ 3.0 mm
Finished pellet: φ 3.0, height 4.0 mm
Tableting machine rotation speed: 15 rpm

(Manufacture of foamed resin moldings)
In the step of kneading and foaming by extrusion molding, for example, in the case of producing a foamed resin molded product as an insulating layer of an insulated wire, the extruder may be an extruder of corrosion resistant specification.

  FIG.4 and FIG.5 is the schematic for demonstrating the manufacturing process of the foamed resin molded object which concerns on embodiment of this invention, and is a schematic for demonstrating the manufacturing process in the case of performing extrusion molding by a master batch system. FIG. FIG. 5 is a schematic view for explaining the state of the pellet 90d in FIG. 4 more easily.

  As shown in FIG. 4, pellets 90 d as a master batch and pellets 90 e consisting of a base resin are loaded from the pellet loading port 81 of the extruder 80, and between the inner wall of the extruder cylinder 82 and the extruder screw 83 Supplied. According to the movement of the extruder screw 83, the pellet 90d and the pellet 90e move in the extruder cylinder 82 (to the right in FIGS. 4 and 5).

4 and pellets by A ₁ area of FIG. 5 is compressed hardly molten, the outer layer 90D and pellet 90e of the pellet 90d at A ₂ regions gradually began to melt, and further the pellet subjected to compression. In B ₁ region, the outer layer 90D and pellet 90e pellet 90d has substantially molten next semi-molten resin 84 begins to chemical blowing agent is decomposed in the inner layer 90b, decomposition gas is generated. In the B ₂ region, the decomposition gas is dissolved in the molten resin 85 which is almost completely melted. Thereby, a foamed resin molded product can be obtained efficiently.

Without the two-layer structure of a pellet 90d according to the embodiment of the present invention, begins to decompose a part of the chemical blowing agent in A ₁ region, decomposition gas is generated from the pellet insertion port 81 into the vaporization (external It may be released (arrow G in FIG. 4). On the other hand, in the case of using the pellet 90d of the two-layer structure according to the embodiment of the present invention, the outer layer 90D functions as a heat insulating material even in the extruder under high temperature and travels the cylinder 82 of the extruder 80. After 90D is melted, the chemical blowing agent in the mixed powder of the inner layer 90b decomposes. At the time of this decomposition, since the extruder cylinder 82 is filled with the semi-molten resin or the molten resin, the decomposition gas is vaporized in the direction of the pellet insertion port 81 by being pressurized by the resin pressure of the extruder 80 and gas-sealed. Since the decomposition gas is dissolved in the molten resin and almost all of the decomposition gas is used for foaming without foaming, a foamed resin molded product can be efficiently obtained.

  The extruder temperature is important in the extrusion of the foam insulated wire. For example, the extruder temperature in the case of using FEP as the high melting point resin is a cylinder temperature of 230 ° C. to 320 ° C. (about 230 ° C. in area A of FIG. Preferably, the head temperature is about 320 ° C. and the die temperature is about 320 ° C. in the region. The extruder temperature in the case of using PFA as the high melting point resin is a cylinder temperature of 260 ° C. to 350 ° C. (about 260 ° C. in area A of FIG. 4 and about 340 ° C. in area B), head temperature of about 350 ° C. It is preferable to set the nozzle temperature to about 340.degree.

[Foam insulation wire / cable]
The foam insulated wire which concerns on embodiment of this invention has an insulating layer which consists of a foamed resin molded object which concerns on embodiment of the above-mentioned this invention.
Moreover, the cable which concerns on embodiment of this invention has a foam insulated wire which concerns on embodiment of this invention.

First Embodiment of the Present Invention
FIG. 6 is a cross-sectional view showing a cross-sectional structure of the foam insulated wire according to the first embodiment of the present invention. FIG. 7 is a cross-sectional view showing a cross-sectional structure of a foam insulated wire according to a modification of FIG. FIG. 8 is a longitudinal side view of the coaxial cable according to the first embodiment of the present invention.

  The foam insulated wire 10 is configured by covering the outer periphery of the internal conductor (strand wire) 1 with a foam insulation layer 2 formed of a foamed resin molded body according to the embodiment of the present invention described above. As shown in FIG. 6, the outer solid layer 3 can be provided outside the foamed insulating layer 2 as needed. Further, as in the case of the foam insulated wire 20 shown in FIG. 7, the internal solid layer 4 can be provided inside the foam insulation layer 2 as needed.

  As the internal conductor 1, a copper wire or a silver plated wire can be used. Not only the stranded wire as shown in FIG. 6 but also a single wire can be used.

  As materials for the outer solid layer 3 and the inner solid layer 4, for example, FEP, PFA, and ETFE can be used.

  The coaxial cable 100 has a configuration in which the outer conductor 101 is provided on the outer periphery of the outer solid layer 3 of the foam insulated wire 10 and the sheath 102 is further covered on the outer periphery thereof.

  The outer conductor 101 can be provided, for example, by winding a copper tape or an aluminum / nylon laminated tape vertically (so-called cigarette winding). Instead of vertical winding, spiral winding may be used. In addition to the tape-shaped one, a copper corrugated pipe, an aluminum straight pipe, an aluminum corrugated pipe, a copper wire braid, a tin-plated copper wire braid, a silver-plated copper wire braid or the like can be used.

  For example, polyvinyl chloride, polyethylene, or flame-retardant polyethylene can be used as the sheath 102.

  In FIG. 8, the cable is configured using only one foam insulated wire 10, but a cable may be configured by covering an outer conductor and a sheath with a collection of a plurality of foam insulated wires 10.

Second Embodiment of the Present Invention
FIG. 9 is a cross-sectional view showing a cross-sectional structure of a foam insulated wire according to a second embodiment of the present invention. FIG. 10 is a longitudinal side view of a coaxial cable according to a second embodiment of the present invention. 11 is a longitudinal side view of a coaxial cable according to a modification of FIG.

  The foam insulated wire 30 shown in FIG. 9 is different from the foam insulated wire according to the first embodiment only in that the internal conductor (single wire) 11 is used instead of the internal conductor (strand wire) 1. .

  The coaxial cable 200 shown in FIG. 10 has a configuration in which the outer conductor 201 is provided on the outer periphery of the outer solid layer 3 of the foam insulated wire 30, and the sheath 102 is further covered on the outer periphery thereof. In FIG. 10, although the outer conductor 201 shows the form using a copper corrugated pipe | tube, a copper tape etc. are made like the coaxial cable 300 shown in FIG. 11 similarly to 1st Embodiment (FIG. 8). The form may be vertically wound.

Third Embodiment of the Present Invention
FIG. 12 is a cross sectional view showing a cross sectional structure of a cable according to a third embodiment of the present invention. FIG. 13 is a cross-sectional view showing a cross-sectional structure of a cable according to a modification of FIG.

  The cable 400 shown in FIG. 12 has a configuration in which two foam insulated wires 10 are arranged in parallel, with the drain wire 402 along the longitudinal direction of the cable, and the outer peripheries thereof are collectively covered with the shielding tape 401. .

  The cable 500 shown in FIG. 13 differs from the cable 400 in that the drain wire 402 is not provided.

  As a material of the shielding tape 401, what is generally used for a cable can be used.

Fourth Embodiment of the Invention
FIG. 14 is a cross-sectional view showing a cross-sectional structure of a foam insulated wire according to a fourth embodiment of the present invention. FIG. 15 is a cross-sectional view showing a cross-sectional structure of a foam insulated wire according to a modification of FIG.

  The foam insulated wire 40 shown in FIG. 14 has two internal conductors (twisted wires) 1 arranged in parallel, and is collectively covered with a foam insulation layer 2 having an elliptical cross-sectional shape that is long in the alignment direction of the two internal conductors 1. This point is different from the foam insulated wire (FIG. 6) according to the first embodiment in that it is.

  Further, the foam insulated wire 50 shown in FIG. 15 does not have an elliptical cross-sectional shape, but has a flat elliptical cross-sectional shape having a flat portion parallel to the alignment direction of the two inner conductors 1.

Fifth Embodiment of the Invention
FIG. 16 is a cross-sectional view showing a cross-sectional structure of a foam insulated wire according to a fifth embodiment of the present invention. FIG. 17 is a cross-sectional view showing a cross-sectional structure of a foam insulated wire according to a modification of FIG.

  The foam insulated wire 60 shown in FIG. 16 has two internal conductors (single wires) 11 arranged in parallel, and is collectively covered with a foam insulation layer 2 having an oval cross-sectional shape long in the direction in which the two internal conductors 11 line up. It differs from the foam insulated wire (FIG. 9) according to the second embodiment in that

  Further, the foam insulated wire 70 shown in FIG. 17 does not have an oval cross-sectional shape, but has a flat oval cross-sectional shape having a flat portion parallel to the alignment direction of the two inner conductors 11.

[Production method of foam insulated wire / cable]
The foam insulated wire and cable according to the embodiment of the present invention use the foamed resin molded article according to the embodiment of the present invention as the insulating layer of the insulated wire according to a known method for producing a foam insulated wire and cable It can be manufactured. Under the present circumstances, it is preferable that the extruder of an outer solid bed is cylinder temperature 230 degreeC-350 degreeC, and head temperature 310 degreeC-350 degreeC. The extrusion method may be performed by a two-layer coextrusion method in which the foamed insulating layer and the outer solid layer are simultaneously extruded, or may be performed by a two-layer common extrusion method in which the foam insulation layer and the outer solid layer are extruded simultaneously.

(Effect of the embodiment of the present invention)
According to the present embodiment, the pellet, the foamed resin molded article, and the foamed insulated wire in which the decomposition gas of the chemical foaming agent can be efficiently used when the high melting point resin having a melting point higher than the decomposition temperature of the chemical foaming agent is used. And cables can be provided. Furthermore, the following effects are achieved.

(1) According to the foam insulated wire and cable having the insulating layer formed of the foam resin molded body according to the present embodiment, a thin foam insulation wire excellent in characteristics such as characteristic impedance, solder heat resistance, deformation rate and drawing force And cables are obtained.

(2) According to the foam insulated wire and cable having the insulating layer made of the foam resin molded body according to the present embodiment, the thickness is excellent in characteristics such as attenuation, VSWR, characteristic impedance, solder heat resistance, deformation rate, and drawing force. A foam insulated wire and cable of diameter are obtained.

  The present invention is not limited to the above embodiment, and various modifications can be made. For example, although a two-layer pellet has been described, it may be a three-layer structure further having an intermediate layer between the inner layer 90b and the outer layer 90D.

(Manufacture of pellet 90d)
The pellet 90d of the present invention was produced according to the following composition. The materials used are as follows.

<Fluororesin>
FEP: trade name NP21, manufactured by Daikin Industries, Ltd. PFA: trade name: AP210), manufactured by Daikin Industries, Ltd.

<Chemical blowing agent>
Azo compound: azodicarbonamide (ADCA): trade name Binihole AC # 3, manufactured by Eiwa Kasei Kogyo Co., Ltd.

<Foaming agent>
Boron Nitride: Brand name Boron nitride (BN) grade name (SP2), manufactured by Denki Kagaku Kogyo Co., Ltd.

  Specifically, powder of chemical foaming agent and foaming nucleating agent is added to powder of FEP or PFA, and mixed with a high-speed flow mixer Super Mixer (trade name: Piccolo SMP-2, manufactured by Kawata Co., Ltd.) The mixture was mixed at 50 rpm for 5 minutes. Thereafter, using a compact tableting machine (HP-AR-SS type, manufactured by Hata Iron Works, Ltd.), the mixed powder has 15 tablets, a tableting diameter (pellet diameter) 2φ mm, a tableting pressure 30MPa, and a tableting tablet Pelletization was performed under the conditions of 50 rpm of machine rotation to obtain an inner layer 90b of pellets.

  Next, using a compact tableting machine (HP-AR-SS type, manufactured by Hata Iron Works, Ltd.), the inner layer 90b of the powder of FEP or PFA and the prepared pellet is 15 tablets, the tableting diameter (pellets) Pelletization is performed under the conditions of diameter 5φ mm, tableting pressure 30MPa, tableting machine rotational speed 50rpm and inner layer 90b coated with outer layer 90D as pellet 90d (FEP or PFA 90% by mass + azo compound) as a master batch (MB) (ADCA) 10% by mass) was obtained.

(Manufacture of high speed transmission cable)
The following high-speed transmission cable (28 AWG) was manufactured using the manufactured pellet 90d under the following conditions.
High melting point resin: FEP
Extruder: 30 mm extruder cylinder: 340 ° C
Head: 320 ° C
Screw: 20 rpm
Resin: MB ratio 1: 20
Chemical blowing agent (mass%): 0.5
Foam nucleating agent (mass%): 0.25
Foam insulation diameter: 1.05φ mm
Wire diameter: 7 / 0.127 = 0.38φ mm
Degree of foaming (%): 50

(Manufacturing of probe cable)
The following ultrasonic diagnostic probe cable (48 AWG) was manufactured using the manufactured pellet 90d under the following conditions.
High melting point resin: PFA
Extruder: 30 mm extruder cylinder: 370 ° C.
Head: 350 ° C
Screw: 20 rpm
Resin: MB ratio 1: 20
Chemical blowing agent (mass%): 0.5
Foam nucleating agent (mass%): 0.25
Foam insulation diameter: 0.093φ mm
Wire diameter: 7 / 0.013 = 0.039φ mm
Degree of foaming (%): 40
Capacitance (pF / m): 117 to 125
Characteristic impedance (Ω): 49 to 53

90a, 90c: Raw material, 90b: Inner layer of pellet 90d: Pellet, 90D: Outer layer of pellet 90e: Pellet (base resin)
90, 900: tableting machine, 91, 91 A: hopper, 92: hopper frame 93: mill, 94: upper punch, 95: lower punch, 96: scraper 97, 98: slider 80: extruder, 81: pellet insertion port , 82: extruder cylinder 83: extruder screw, 84: semi-molten resin, 85: molten resin 10, 20, 30, 40, 50, 60, 70: foam insulated wire 1, 11: internal conductor, 2: foam insulation Layer 3: External solid layer 4: Internal solid layer 100, 200, 300: Coaxial cable 101, 201: Outer conductor 102: Sheath 400, 500: Coaxial cable 401: Shield tape, 402: Drain wire

Claims (1)

A method for producing a pellet for molding a foamed resin, comprising: an inner layer containing a high melting point resin and a chemical blowing agent; and an outer layer covering the inner layer and containing a high melting point resin having a melting point higher than the decomposition temperature of the chemical blowing agent. And
Charging the powder of the high melting point resin for the outer layer into a first hopper of a tableting machine;
Charging the material for the inner layer formed into a pellet by mixing the powder of the high melting point resin and the powder of the chemical foaming agent into a second hopper of the tableting machine;
A first weighing step of weighing the powder of the high melting point resin in the first hopper into a die;
Feeding the inner layer material in the second hopper onto the powder of the high melting point resin in the die;
A second weighing step of weighing the powder of the high melting point resin in the first hopper into the die so as to cover the inner layer material in the die;
A pressing step of pressing and pelletizing the raw material for the inner layer and the powder of the high melting point resin in the die with an upper and lower crucible;
The manufacturing method of the pellet for foamed resin molding provided with this.

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