CN1008051B

CN1008051B - Band production method and its product by means of automatic temp. limit heating

Info

Publication number: CN1008051B
Application number: CN 87102924
Authority: CN
Inventors: 苏洪; 蒋淮渭
Original assignee: University of Science and Technology of China USTC
Current assignee: University of Science and Technology of China USTC
Priority date: 1987-04-19
Filing date: 1987-04-19
Publication date: 1990-05-16
Also published as: CN87102924A

Abstract

The present invention discloses a manufacturing method for an automatic temperature-limited heating band and a product thereof. A heating element of the heating band uses two long metal wire cores with the same space as electrodes; a temperature sensitive electric switch material layer, namely a PTC material layer is continuously laid on the electrodes to be used as a heating unit, and the switch temperature TS of the material is 85 DEG C +/-5 DEG C; an electrothermal element is covered with a macromolecular sheath; a heating band finished product is formed by integral radiation crosslink. The product has the thermal properties of electric heating, power self regulation and automatic temperature limit, and the limited temperature (Tr) is 80 DEG C +/-5 DEG C. The present invention can be widely used for the freeze prevention and the coagulation prevention of petroleum and chemical industry departments, and the heating insulation work of transport pipelines for gas and liquid, etc.

Description

Band production method and its product by means of automatic temp. limit heating

The present invention relates to the manufacturing process and the electric heating device thereof of electrothermal device.

The electric heating element of tradition electric heater is to use metallic resistance material as heater, and its resistivity varies with temperature less, and under rated voltage, electric thermal power is constant substantially.Have only by adding control electronics, could realize the automatic adjusting of power, but the technology more complicated, cost is higher, and inconvenience is safeguarded.F.Kohler in 1961 finds that with the composite material that low-pressure polyethylene (HDPE) filling carbon black (CB) makes its resistivity has positive temperature coefficient (Positive Temperature Coefficient), is called for short ptc material.The resistivity of this material not only raises with temperature and increases, and sharply increases in a leap at specific warm area, so that can block electric current, has the heat-sensitive electric switch characteristic.The temperature that its resistivity is increased in a leap is defined as the switch temperature (Ts) of ptc material.Different ptc materials, its switch temperature (Ts) difference, it depends primarily on raw material and forms and manufacturing process.U.S.'s use ptc material is early made from the prototype (USP3,243,753) of limitting heater as heater.With the heater of limit certainly that ptc material is made, during energising work, not only can heat, and can limit maximum heating temperature automatically, this temperature is defined as the temperature of limit certainly (Tr) of heater.From the height of limit temperature (Tr), depend on the switch temperature (Ts) of ptc material, it can make the maximum heating temperature of heater stably be operated near the Ts.R is a leading indicator of self-limiting heater temperature from the limit temperature T, and it has determined the accommodation of heater.The U.S. in 1974 has developed and has been fit to the heater of limit certainly (being Self-Regu-lating Heater) that industry is used.At USP3,914, in 363 patent documentations, disclosed manufacture method from limit conduction extrudate, make the heater of making under 120～150 ℃ of temperature, to anneal more than 15 hours, thereby require the fusing point of the lagging material (high polymer) of heater must be than high tens degree of inner ptc material, to guarantee under annealing temperature not softening transform of PTC electric heating element.At present, external (as the U.S.) commercialization to produce Tr be 65 ℃, 110 ℃, 120 ℃ and 150 ℃ are different types of from limitting heaters.Domesticly since 1980 begin to involve in above-mentioned field, develop the heating tape of limit certainly that Tr equals 65 ℃.Because described heater (band) has automatic limit temperature, the property of compensation heating now has been widely used in antifreeze, anti-condensing, gas-liquid transports pipeline, and oil exploitation etc. are many to be needed on the engineering of heat tracing, has obtained the excellent effect of generally acknowledging.Aspect civilian, also obtain more and more widely Application and Development from the limit heater, cause the attention of domestic and international science and technology and business circles, people explore the heating efficiency (the clear 57-12061 of JP) of ptc material from many aspects, the working life (the clear 55-98801 of JP) of electric conductivity (the clear 57-21441 of JP, the clear 56-8443 of JP) and heater etc.But, still lack Tr=80 ℃ the heater of limit certainly in prior art and the commodity, more do not disclose the production technology of this kind heater.

At above-mentioned situation, task of the present invention is the production method that proposes a kind of automatic temperature-limiting heater, and to have used switch temperature (Ts) be that 85 ℃ ptc material is as heater, produce the heating tape of limit certainly that maximum heating temperature can be limited to automatically 80 ± 5 ℃ of warm areas, to satisfy of the requirement of civilian and various heat insulating works to this warm area heater.

Main points of the present invention are: between two tool parallel metal cores at regular intervals, lay ptc layer continuously equably, form electric heating element PTC core band.Coat one deck (or multilayer) macromolecular material (or metal knitted net) as the heating tape overcoat in this core band outside again, at last heating tape integral body is carried out cross-linking radiation, make the ptc characteristics of core have memory function, promptly make from limitting the heater finished product.Said metal core is optional with two electrodes of stranded wire as the heating tape.PTC core band uses similar thermoplastic polymer (PE) to make base material with the macromolecule overcoat.The present invention finishes through drawing PTC core band, coating outer cover and cross-linking radiation three-procedure.Its production stage is:

A. draw the core band: the single multiple screw extruder of preheating at first, and keep 210～250 ℃ of the head temperatures of this plastic extruding machine, 150～180 ℃ of body temperatures, 80～110 ℃ of tail temperature.The pellet that with switch temperature (Ts) is 85 ± 5 ℃ ptc material is again packed into from tail.Pass the head extruded mould abreast with two equidistant conductor wire cores, draw this core uniform motion simultaneously, its linear velocity is stabilized in 30～50m/min, along with the displacement of core ground, plastic extruding machine is extruded the viscous state ptc material continuously by extrusion die, and on these two cores that are laid in equably, forms the banding pattern electric heating element that there is two parallel poles (being core) ptc material tail and both sides, again the hot electric heating element that is drawn is cooled off through tank, PTC core band.

B. coating outer cover: the macromolecule lagging material, can select polyethylene from high pressure process (LDPE) class cable sheath material for use.With above-mentioned homotype plastic extruding machine, 210～230 ℃ of head temperatures that keep this plastic extruding machine, 150～170 ℃ of body temperatures, 90～100 ℃ of tail temperature are coated with an amount of talcum powder with the PTC core band of above-mentioned drawing, pass the outer mold of head, the outlet shape of this mould is consistent with core band mould (cross section), size is big slightly, passes the PTC core band of outer mold, and its draught line speed is with the draw rate of PTC core band.Along with the core band pull out, viscous state protective cover material in the plastic extruding machine is extruded on the PTC core band the hot overcoat of formation continuously equably through outer mold, pass through the roll forming of a pair of column type roller again, make it be close to PTC core belt surface, enter the tank cooling immediately, obtain the basic model heating tape.

C. crosslinking with radiation: the PTC core band with above-mentioned coating outer cover, at normal temperature, normal pressure, place radiation field under the air atmosphere, carry out evenly cross-linking radiation of integral body.Radiation source available electron bundle or ⁶⁰Co, ¹³⁷Gamma-rays such as Cs.During irradiation,, when the accumulation irradiation dose of band body reaches 5～20Mrad, can stop irradiation according to used radiation source difference.The degree of cross linking of its ptc material and overcoat should promptly be finished from the production process of limitting the heating tape in 45～65% scopes.

Automatic siding temperaturing heating belt by above-mentioned steps production, be to have the PTC core band and the overcoat of two electrodes to constitute by both sides, certainly the limit temperature (Tr) of this heating tape is 80 ± 5 ℃, its core band uses similar thermoplastic polymer (PE) to make base material with the macromolecule overcoat, behind whole cross-linking radiation, its degree of cross linking is 45～65%.Deadweight about 40g/m in heating tape is suitable for conventional AC and DC power supply, operating voltage 220 ± 20V.Its power output varies with temperature and can regulate automatically.This heating tape continuous operation life-span is greater than 30,000 hours, and the discontinuous operation life-span is greater than 2,000 times (energising, outage circulation for once).The heating tape finished product limits temperature to distribute all 80 ± 5 ℃ of scopes along band height degree with the test of AGA780 type thermal imaging system certainly, through related detection unit press GB2951, that the GB3048 standard method is tested is all qualified.And on probation through units concerned, respond well, the departments such as industry, national defence that can be widely used in need on the engineering of heat tracing.Also can make the heat tracing device of other shape as required, to adapt to various special purposes.

Description of drawings:

Fig. 1 is the basic structure of a kind of embodiment of automatic siding temperaturing heating belt, and wherein 1 is electrode, and 2 is ptc layer, and 3 is overcoat.

Fig. 2 is a PTC core band A-A profile among Fig. 1, and 1 is electrode, and 2 is ptc layer.

Fig. 3 is automatic siding temperaturing heating belt electric thermal power P(W/m) with temperature T (℃) relation that changes.

Embodiment: make the core carrying raw material with Ts=85 ± 5 a ℃ ptc material, core is selected 2401 black polyvinyl cable protective cover materials (PE-H) for use with the regular twisted wire of 19 strands of zinc-plated circular copper wires, per share circular copper wire φ=0.26mm, overcoat, draw core band and coating outer cover with φ 45 single multiple screw extruders, use ⁶⁰Co gamma ray projector cross-linking radiation, cumulative dose stops irradiation to 15Mrad, measures the degree of cross linking with soxhlet's extractor, and the degree of cross linking is greater than 45%.Use above-mentioned production stage, the temperature of plastic extruding machine is seen the literary composition back as table 1():

The PTC core band that embodiment 1～4 draws is when coating outer cover, and the plastic extruding machine temperature all remains on 230 ℃ of heads, 170 ℃ on fuselage, 100 ℃ of tails.

Embodiment 1234

Draw PTC head 220 210 220 250

Core band temperature (℃) fuselage 170 150 160 180

Tail 90 80 90 110

Claims

1, a kind of automatic siding temperaturing heating belt production method, this method is that to carry out integral body with radiation method crosslinked, the electric heating element that it is characterized in that the heating tape, using switch temperature (Ts) is that 85 ± 5 ℃ ptc material is raw material, its overcoat uses the thermoplastic macromolecule material similar with ptc material (PE) to be base material, and production stage is:

A. draw the core band

(1) the single multiple screw extruder of preheating, and keep 210～250 ℃ of head temperatures, 150～180 ℃ of body temperatures, 80～110 ℃ of tail temperature; From tail

(2) switch temperature (Ts) of packing into is 85 ± 5 ℃ a ptc material pellet;

(3) pass the extruded mould of head abreast with two equidistant conductor wire cores, the draught line velocity-stabilization that makes this core is at 30～50m/min; Simultaneously

(4) plastic extruding machine is extruded the viscous state ptc material by extrusion die, on these two cores that are laid in equably continuously, forms the banding pattern electric heating element that there are two parallel poles ptc layer and both sides;

(5) the hot electric heating element that (4) are drawn cools off through tank, promptly becomes PTC core band.

B. coating outer cover is selected polyethylene from high pressure process (LDPE) class cable jacket material for use

(6) used plastic extruding machine is with (1), and the temperature that extrudes overcoat keeps 210～230 ℃ of heads, 150～170 ℃ on fuselage, 90～100 ℃ of tails.

(7) the PTC core band that (5) are drawn is coated with an amount of talcum powder, passes the outer mold that size is big slightly, export shape same (3); And make

(8) this PTC core band draught line speed is with (3); Simultaneously

(9) the viscous state protective cover material in the plastic extruding machine is extruded on the core band through outer mold; Again

(10) through the roll forming of a pair of column type roller, make it be close to PTC core belt surface; Enter immediately

(11) heating tape basic model body is made in tank cooling.

C. crosslinking with radiation

(12) with the heating tape of (11) coating outer cover, under normal temperature, normal pressure, air atmosphere, place and carry out whole irradiation in the radiation field;

(13) look used radiation source classification, wait to accumulate the irradiation accumulated dose when reaching 5～20Mrad, irradiation stops.Make from limitting the heating tape finished product.

2, production method according to claim 1 is characterized in that made basic model heating tape behind whole irradiation, and its PTC core and the overcoat degree of cross linking are 45～65%.

3, the automatic siding temperaturing heating belt that utilizes claim 1,2 methods to produce, this heating tape is to have the PTC core band and the overcoat of two electrodes to constitute by both sides, the temperature of limit certainly (Tr) that it is characterized in that said heating tape is 80 ± 5 ℃, said core band and overcoat use similar thermoplastic polymer (LDPE) to make base material, and its degree of cross linking is 45～65%.