JP2008132663A - Manufacturing method of curled cord - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for developing a curled cord to withstand use in cold region or the like by using heat vulcanization type silicone rubber excellent in heat resistance and cold resistance or the like, and solving various problems of molding to be caused during the manufacturing. <P>SOLUTION: The manufacturing method of the curl cord comprises: (a) a step where an organic peroxide is added and agitated with a millable silicone rubber having polymerization degree of 5,000-10,000, and the agitated silicone rubber is coated on wire core by an extruder to make a string-like molded body; (b) a step where the string-like molded body is heated to harden only its surface part; (c) a step where the string-like molded body having the hardened surface is wound to a bobbin with grooves where the grooves is spirally carved with a constant interval; and (d) a step where the string-like molded body wounded to the bobbin is heated to harden the whole part in a curl shape. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a curl cord manufacturing technique, and more particularly to a curl cord manufacturing method for imparting spring properties to an elastic silicone rubber having heat resistance and cold resistance.

Curl cords make use of their spring characteristics and are used in curl holders for mobile phones, windings for sensors attached to aircraft doors, bus doors, etc., and the materials used are generally vinyl chloride and polyester for thermoplastic resins. In the thermosetting resin, urethane type or synthetic rubber type is used, and each is used properly according to the application. However, the spring characteristics are maintained at 100% resilience and high durability in the initial stage of use, but gradually deteriorate with long-term use, especially in cold regions such as Hokkaido and high temperature regions such as Okinawa and desert. The degradation temperature is fast and the usable temperature range of inexpensive vinyl chloride is usually limited to about −5 to + 55 ° C.
For example, Patent Document 1 discloses that “a hand strap attached to a portable article such as a mobile phone and a method for manufacturing the hand strap, a synthetic resin material such as urethane or vinyl chloride has a transparent feeling and can be given various colors. Since it is possible, "what distinguishes a mobile phone to be used from others by design or its color" has been proposed. However, this type of proposal is limited to a temperature range that can be carried by a person, and when used in a cold region, the hand strap will shrink and lose its springiness. Conversely, in a high temperature region exceeding + 55 ° C. The resin may be softened and stretched out.
Patent Document 2 states that “the material to be used is a wire core having a diameter of 1 to 2 mm composed of a plurality of metal strands, and the periphery thereof is covered with a high-strength braid formed of para-aramid fibers, and further to the outside. Is coated with a thermoplastic resin comprising a polyester resin, a vinyl chloride resin, a styrene resin, a polyamide resin, an olefin resin, and a fluorine resin to form a curled high shear cord and curl cord. Proposed. However, this is intended for high shear, and a fluororesin or the like is not suitable at low temperatures even though it has elasticity at high temperatures.
Therefore, in a cold region such as Hokkaido and a high temperature region such as Okinawa, it cannot be a curled cord having a spring property that always has heat resistance while maintaining heat resistance and cold resistance.
JP 2000-157321 A JP 2002-339280 A

The present invention was manufactured in view of the above circumstances, using a heat vulcanization type silicone rubber excellent in heat resistance, cold resistance, etc., and developing a curl cord that can withstand use in the cold region, etc. It is an object of the present invention to provide a curl cord manufacturing technique capable of solving various molding problems that occur during the manufacturing.

In order to achieve the above object, the method for producing a curl cord according to claim 1 is: (a) adding and mixing an organic peroxide to a millable silicone rubber having a polymerization degree of 5000 to 10,000; A step of covering the wire core with an extrusion molding machine to form a string-shaped molded body, (b) a step of heating the string-shaped molded body to cure only the surface portion, and (c) the surface is cured. A step of winding the string-shaped molded body around a grooved bobbin in which grooves are formed in a spiral shape at regular intervals, and (d) heating the string-shaped molded body wound around the bobbin to curl the whole. And (e) a step of allowing the string-shaped molded body to be stabilized at a constant temperature, and (f) a step of reversing the curl direction of the string-shaped molded body removed from the bobbin. To do.

In the curl cord manufacturing method according to the second aspect of the present invention, the heating temperature is set to 90 to 120 ° C. and the heating application time is set to 30 to 60 seconds when the surface portion of the string-like molded body is cured.

According to a third aspect of the present invention, there is provided a grooved bobbin in which a spiral groove is engraved with a space between the grooves being about 1 mm when the grooved bobbin is formed.

Since the present invention is mainly made of silicone rubber, a curl cord having a spring property that always has heat resistance while maintaining heat resistance and cold resistance in a wide temperature range of −45 to + 115 ° C. is obtained. It can withstand repeated use in cold regions of Hokkaido and hot regions of Okinawa.
Since the silicone rubber is a millable silicone rubber having a degree of polymerization of 5000 to 10000, it is possible to mix with a roll, and to suppress dripping of the rubber after molding by an extrusion molding machine, thereby enabling subsequent processing.
Since only the surface portion is cured by hot air after extrusion by the extruder, the surface of the silicone rubber is cured to prevent dripping and enables winding on a bobbin. On the other hand, since the inside of the silicone rubber is maintained in an uncured state, curling by winding around the bobbin is enabled.
Since the bobbin is a grooved bobbin in which grooves are engraved in a spiral shape at a constant interval, it is possible to avoid mutual fusion due to close contact when wound in a spiral shape, and at an appropriate interval. Therefore, after curing, it is possible to maintain a spiral shape in which they are adhered and extended by elasticity.

An embodiment of the present invention will be described based on FIGS. 1 to 3 and Tables 1 to 3. FIG.
The present invention forms a curl cord having heat resistance, cold resistance, elasticity, and springiness. The characteristics of the molding method will be described in which millable silicone rubber and a crosslinking agent are used as the selection material and attention is paid to appropriate viscosity as a mixture of the two.

The silicone rubber used as the raw material of the present invention is a millable silicone rubber having a net-like molecular structure having a siloxane bond. The degree of polymerization of the rubber is 5000 to 10,000, and an organic peroxide crosslinking agent is blended through a roll operation. It is a viscous polymer that can be stirred. That is, the silicone rubber having a polymerization degree of 5000 to 10,000 is not so hard that it is difficult to roll, and on the other hand, it does not become soft enough to cause dripping after stirring, and acquires appropriate millability. It has a viscosity that can.
It is an insulating elastic body having heat resistance and cold resistance in terms of physical properties, specifically, a heat resistance and cold resistance of −45 to + 115 ° C. The characteristics are shown in Table 1. The measuring method was based on JISK6249.

Next, as the crosslinking agent added to the millable silicone rubber, an organic peroxide, particularly p-methylbenzoyl peroxide was used in the present invention. Mixing and stirring to form an appropriate viscosity together with the silicone rubber during the molding process, the viscosity decreases with time of mixing and extrusion, and after a certain period of time, the viscosity stabilizes and elasticity and spring after heating The material was selected as a material capable of removing the excess peroxide remaining by performing final heating after the thermoforming process, and capable of removing the remaining peroxide.

Based on the characteristics of each material described above, a blending table of materials for molding a curl cord having heat resistance, cold resistance, elasticity, and spring property according to the present invention is described in Table 2, and the molding method is described. .

A molding method for producing the curl cord will be described below based on the above recipe.
First, a predetermined amount of millable silicone rubber was charged into a roll mill, and while rotating the mill, a predetermined amount of p-methylbenzoyl peroxide was charged, and both were mixed and stirred. Since the surface state of the mixture is uncured, it exhibits a sticky state.

Next, the state of the extrusion molding process is shown in FIG.
The silicone mixture 1 is put into the cylinder 3 of the coaxial extruder 2, a wire core 4 such as an electric wire is inserted from the rear of the coaxial extruder 2, and the silicone mixture 1 is concentrically formed on the wire core 4. While being covered, the nozzle 5 is discharged as a coaxial extruded string-like molded body 6.
At this time, since the millable silicone rubber having a polymerization degree of 5000 to 10000 was stirred by the roll, there was no sag or undulation during extrusion. In other words, the silicone rubber having a polymerization degree of less than 5000 has a viscosity that is too low and sags in the extrusion. Conversely, in the case of a silicone rubber having a polymerization degree of 10,000 or more, the viscosity becomes too high and the surface of the molded product is corrugated. However, silicone rubber does not have such a difficulty within the above-mentioned polymerization degree range, and an appropriate viscosity is maintained.

FIG. 2 shows an enlarged cross-sectional view of the coaxial extruded string-like molded body 6 formed in the extrusion process. This figure is a cross-sectional view of a cable for a two-core curl cord with a diameter of 4.5 mm. The wire core 4 such as an electric wire has two cores, and the same two-core polyester elastomer insulator 7 and four cores are formed. Winding and one wire core. The state where the silicone rubber 9 is coated on the wire core by the extruder is shown.
Next, only the surface portion is cured by applying hot air to the surface of the string-shaped molded body 6 or immersing it in warm water.
That is, for example, if the surface of the string-like molded body 6 is immersed in warm water of 90 ° C. for 60 seconds or hot air of 150 ° C. is applied for 25 seconds, the surface of the silicone rubber undergoes a crosslinking reaction, and the soft surface is cured and the whole is cured. Keeps a certain shape. On the other hand, since the reaction time is set to a short time below a certain level, the inside does not reach the cross-linking reaction and maintains the viscosity.
As a result of the surface layer cross-linking, the silicone rubber stops only at the cross-linking of the surface layer portion, and only the surface layer portion is cured, and the cross-linking from the surface layer portion to the inside does not proceed. That is, the surface layer of the silicone rubber exhibits a smooth state and can be wound around a bobbin described later, while the inside still exhibits a sticky state, and this sticky state causes the coating on the wire core to be in close contact. It is possible to cure the silicone along the groove of the bobbin by a cross-linking reaction which will be described later to obtain a spiral elastic rubber body.

The string-like molded body 6 whose surface layer part is crosslinked in the main crosslinking pretreatment process is wound around a bobbin 10 with a spiral groove and molded. The bobbin is shown in FIG. The outer diameter of the bobbin 10 is set to 11 mmφ in accordance with the outer diameter of the curl cord to be finally formed, the length is 400 to 500 mm, and a semicircular groove having a diameter of 4.5 mmφ is formed on the outer periphery thereof. Then, a spiral groove having a pitch of 5.5 mm is cut, and an interval of about 1 mm is provided between the spiral grooves.
This interval of 1 mm can be avoided because the silicone rubber 9-coated extrusion-molded product is spirally wound at the time of heat-crosslinking and is fused to each other by close contact.
The bobbin 10 is set on a winding machine, the pretreated silicone rubber 9 having a diameter of 4.5 mmφ is wound along the spiral groove, and is cross-linked by an electric furnace. For example, the electric furnace temperature is 120 to 150 ° C., and the electric furnace application time is 15 to 20 minutes.

After removing the string-like molded body 6 from the spiral grooved bobbin 10, it is crosslinked in a thermostatic bath at a temperature of 140 to 160 ° C. for an application time of 50 to 70 minutes, and the residue of the vulcanizing agent in the silicone rubber is removed. Deterioration such as cracks generated by hydrolysis due to secular change is prevented, and the inherent rubber-like elasticity is retained.

In the cross-linking stabilization step, after the rubber-like elasticity inherent in the silicone rubber is retained, the spiral-shaped direction is reversely rotated in order to impart higher spring properties. If the reverse rotation is not performed, the spring property is not enhanced.

Next, examples will be described. 1.5 parts of p-methylbenzoyl peroxide were put into a roll mill and mixed with 100 parts of millable silicone rubber having a polymerization degree of 5,000 to 10,000. A string-shaped molded body having a thickness of 1.25 mm and a diameter of 4.5 mm was formed by covering the wire core with an extrusion molding machine. A wire core was formed by forming a core with a 2-core electric wire and a 2-core polyester elastomer insulator and winding a paper tape. This was immersed in warm water at 90 ° C. for 60 seconds. The string-like molded body was wound around a bobbin having a semicircle with a groove depth of 4.5 mm, a groove interval of 1 mm and a length of 400 mm, and maintained at 120 ° C. for 20 minutes in an electric furnace. The molded body removed from the bobbin was left in a thermostatic bath at 150 ° C. for 1 hour, and finally the direction of the spiral was reversed to obtain a curled cord.
As characteristics of the curl cords obtained in the above examples, Table 3 shows heat resistance and Table 4 shows cold resistance. This characteristic value is a value measured in accordance with JISK6249 after being left in an atmosphere having a heat resistance of 220 ° C. for 96 hours after crosslinking of the silicone rubber.

Furthermore, the electrical standard of the cable for the two-core curl cord could be passed. The characteristic values are shown in Table 5.

The curl cord of the present invention is sufficient as a curl cord having a spring property that maintains heat resistance and cold resistance even when left in a harsh atmosphere of −45 to + 115 ° C. and always has elasticity in a wide temperature range. It can be used and can be widely used for ships, airplanes, and the like.

FIG. 1 shows a schematic diagram of the coaxial extrusion process of the present invention. FIG. 2 is an enlarged cross-sectional view of a cable for a two-core curl cord having a diameter of 4.5 mmφ. FIG. 3 shows a spiral grooved bobbin.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Silicone agitation 2 Coaxial extruder 3 Cylinder 4 Wire core 5 Nozzle 6 Coaxial extrusion string-like molded object 7 Polyester elastomer insulator 8 Paper tape 9 Silicone rubber 10 Spiral grooved bobbin

Claims (3)

(A) adding an organic peroxide to millable silicone rubber having a degree of polymerization of 5000 to 10000, stirring the mixture, and coating the stirred silicone rubber on a wire core with an extruder to form a string-like molded body; ,
(B) heating the string-like molded body to cure only the surface portion;
(C) a step of winding the string-shaped molded body having the surface hardened around a grooved bobbin in which grooves are engraved spirally at a constant interval;
(D) heating the string-like molded body wound around the bobbin to cure the whole in a curled shape;
(E) a step of stabilizing the string-like molded body by leaving it at a constant temperature;
(F) a step of reversing the curling direction of the string-like molded body removed from the bobbin;
A curl cord manufacturing method comprising: The method for producing a curl cord according to claim 1, wherein when the surface portion of the string-like molded body is cured, the heating temperature is 90 to 120 ° C and the heating application time is 30 to 60 seconds. 2. The method of manufacturing a curled cord according to claim 1, wherein in forming the grooved bobbin, the bobbin is formed by forming a spiral groove in which a space between the grooves is maintained at about 1 mm.