Magnet for anti-theft label and preparation method thereof

Abstract

The invention relates to a magnet for an anti-theft label, and the magnet for the anti-theft label comprises the following components in percentage by mass: 70wt%-85wt% of magnetic powder, less than or equal to 2wt% of auxiliary materials and the balance of a binder, the magnetic powder comprises first magnetic powder and second magnetic powder in a mass ratio of (1-1.5): 1; the first magnetic powder is samarium-iron-nitrogen magnetic powder; the second magnetic powder is iron powder; the residual magnetism of the magnet for the anti-theft label is 170 mT to 185 mT, and the coercive force of the magnet for the anti-theft label is 420 KA / m to 450 KA / m. Through cooperation of the first magnetic powder and the second magnetic powder, the obtained magnet for the anti-theft label has residual magnetism of 170 mT to 185 mT and coercive force of 420 KA / m to 450 KA / m, is easy to demagnetize and not easy to interfere, and can achieve the purpose of preventing fraud brushing.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic materials, and relates to a magnet material with relatively high coercivity and remanence, and particularly relates to a magnet for anti-theft labels and a preparation method thereof. Background Art

[0002] The magnetic materials used in anti-theft labels are usually made of ferrite, and this kind of material is relatively sensitive to magnetic fields. When a commodity with a magnetic anti-theft label passes through the induction area, if the commodity is not paid for normally, the magnet in the anti-theft label will be activated, changing its internal circuit state, and then triggering a signal. This signal matches the anti-theft system installed in the store. If the signal is inconsistent, the alarm system will be triggered. Although the anti-theft labels made of traditional ferrite materials can achieve the anti-theft function, their material coercivity is relatively low and they are easily magnetized and demagnetized by strong magnetic fields, resulting in the theft of goods being swiped.

[0003] CN108624824A discloses a bias sheet, a manufacturing method thereof, and an acoustic magnetic anti-theft label made therefrom. The bias sheet is made of a cold-rolled strip of an alloy of Fe with one or more transition metals with a total of no more than 8 wt% of Co of 7 wt%-11 wt%, Cr of 20 wt%-23 wt%, and is obtained by aging heat treatment at 460 °C or above for more than 30 minutes, with a thickness of 0.05 mm - 0.12 mm and a DC magnetic property of remanence of 10000 Gs - 14500 Gs and coercivity of 15 Oe - 38 Oe. It uses an FeCrCo alloy to make a bias sheet with optimal coercivity, high remanence, and high squareness ratio, but the cost is relatively high and the preparation process is complex, making it difficult to be applied industrially.

[0004] Therefore, it is necessary to provide a magnet for anti-theft labels and a preparation method thereof different from the prior art, which not only makes the preparation method simple and easy to implement, but also enables the obtained magnet for anti-theft labels to have appropriate remanence and appropriate coercivity, so as to achieve the purpose of being easily demagnetized and not easily interfered. Summary of the Invention

[0005] Aiming at the deficiencies existing in the prior art, the purpose of the present invention is to provide a magnet for anti-theft labels and a preparation method thereof. The magnetic powder for anti-theft labels provided by the present invention has appropriate remanence and appropriate coercivity, so as to achieve the purpose of being easily demagnetized and not easily interfered, and can achieve the purpose of preventing theft by swiping.

[0006] To achieve the purpose of this invention, the present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention provides a magnet for anti-theft labels. In terms of mass percentage, the preparation raw materials of the magnet for anti-theft labels include 70 wt%-85 wt% of magnetic powder, ≤2 wt% of auxiliary materials, and the balance of binder.

[0008] The magnetic powder includes a first magnetic powder and a second magnetic powder with a mass ratio of (1 - 1.5):1.

[0009] The first magnetic powder is samarium iron nitride magnetic powder.

[0010] The second magnetic powder is iron powder.

[0011] The remanence of the magnet for the anti-theft label is 170 mT - 185 mT, and the coercivity is 420 kA / m - 450 kA / m.

[0012] The first magnetic powder used in the present invention has the characteristic of high coercivity, providing a relatively high coercivity for the magnet of the anti-theft label; the second magnetic powder used in the present invention has a low cost and wide sources. By mixing with the first magnetic powder, the resulting magnet for the anti-theft label has a remanence of 170 mT - 185 mT and a coercivity of 420 kA / m - 450 kA / m, is easily demagnetized and not easily interfered, and can achieve the purpose of preventing fraudulent swiping.

[0013] By mass percentage, the preparation raw materials of the magnet for the anti-theft label include 70 wt% - 85 wt% of magnetic powder, such as 70 wt%, 72 wt%, 75 wt%, 80 wt% or 85 wt%, but not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0014] By mass percentage, the preparation raw materials of the magnet for the anti-theft label include ≤2 wt% of auxiliary materials, such as 0.5 wt%, 1 wt%, 1.5 wt% or 2 wt%, but not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0015] In the magnetic powder of the present invention, the mass ratio of the first magnetic powder to the second magnetic powder is (1 - 1.5):1, such as 1:1, 1.2:1, 1.3:1, 1.4:1 or 1.5:1, but not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0016] When the dosage of the first magnetic powder is too small, the coercivity of the finally obtained magnet for the anti-theft label is relatively low; when the dosage of the first magnetic powder is too large, the second magnetic powder cannot play a good filling effect, resulting in a slight decrease in the coercivity of the magnet for the anti-theft label.

[0017] Preferably, the remanence of the samarium iron nitride magnetic powder is 350 mT - 380 mT.

[0018] The remanence of the samarium iron nitride magnetic powder used in the present invention is 350 mT - 380 mT, such as 350 mT, 355 mT, 360 mT, 370 mT or 380 mT, but not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0019] Preferably, the coercivity of the samarium-iron-nitrogen magnetic powder is 880 KA / m - 920 KA / m. For example, it can be 880 KA / m, 890 KA / m, 900 KA / m, 910 KA / m, or 920 KA / m, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0020] Preferably, the binder includes any one or a combination of at least two of chloroprene rubber, ethylene-propylene rubber, nitrile rubber, chlorinated polyethylene (CPE), ethylene-vinyl acetate copolymer (EVA), or thermoplastic elastomer (TPE). Typical but non-limiting combinations include a combination of chloroprene rubber and ethylene-propylene rubber, a combination of nitrile rubber and CPE, a combination of CPE, EVA, and TPE, or a combination of chloroprene rubber, ethylene-propylene rubber, nitrile rubber, CPE, EVA, and TPE.

[0021] Preferably, the auxiliary materials include any one or a combination of at least two of stearic acid, calcium stearate, coupling agent, or plasticizer. Typical but non-limiting combinations include a combination of stearic acid and calcium stearate, a combination of calcium stearate and coupling agent, a combination of coupling agent and plasticizer, or a combination of stearic acid, calcium stearate, coupling agent, and plasticizer.

[0022] Preferably, the coupling agent includes any one or a combination of at least two of aluminate coupling agent, titanate coupling agent, or aluminate-titanium composite coupling agent. Typical but non-limiting combinations include a combination of aluminate coupling agent and titanate coupling agent, a combination of titanate coupling agent and aluminate-titanium composite coupling agent, or a combination of aluminate coupling agent, titanate coupling agent, and aluminate-titanium composite coupling agent.

[0023] Preferably, the plasticizer includes epoxy soybean oil and / or phthalate plasticizer.

[0024] In a second aspect, the present invention provides a method for preparing a magnet for an anti-theft tag, and the preparation method includes the following steps:

[0025] Mix the magnetic powder, binder, and auxiliary materials according to the formula amounts, and then successively carry out internal mixing, open mixing, extrusion molding, and magnetization to obtain the magnet for an anti-theft tag described in the first aspect.

[0026] Preferably, the temperature of the internal mixing is 80°C - 125°C. For example, it can be 80°C, 90°C, 100°C, 110°C, 120°C, or 125°C, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0027] Preferably, the absolute pressure of the internal mixing is 2 MPa - 5 MPa. For example, it can be 2 MPa, 2.5 MPa, 3 MPa, 4 MPa, or 5 MPa, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0028] Preferably, the temperature of the open mill is 50°C - 55°C. For example, it can be 50°C, 51°C, 52°C, 53°C, 54°C, or 55°C, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0029] Preferably, the temperature of the extrusion molding is 50°C - 130°C. For example, it can be 50°C, 60°C, 80°C, 90°C, 100°C, 110°C, 120°C, or 130°C, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0030] The extrusion molding in the present invention is carried out in an extruder. There are three temperature zones arranged along the axial direction of the screw, corresponding to the first temperature, the second temperature, and the third temperature respectively. Under the condition of the first temperature, the material is preliminarily heated to start softening; under the condition of the second temperature, the material is better mixed and heated evenly, and the fluidity of the material is further enhanced; under the condition of the third temperature, the material reaches an ideal extrusion state, ensuring that the material can be smoothly extruded and has good molding quality.

[0031] Preferably, the first temperature is 50°C - 60°C. For example, it can be 50°C, 52°C, 55°C, 58°C, or 60°C, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0032] Preferably, the second temperature is 95°C - 100°C. For example, it can be 95°C, 96°C, 98°C, 99°C, or 100°C, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0033] Preferably, the third temperature is 110°C - 130°C. For example, it can be 110°C, 115°C, 120°C, 125°C, or 130°C, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0034] Preferably, the extrusion speed of the extrusion molding is 200 r / min - 500 r / min. For example, it can be 200 r / min, 250 r / min, 300 r / min, 400 r / min, or 500 r / min, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0035] Preferably, the magnetizing capacitor used for magnetizing is 4000 μF - 8000 μF. For example, it can be 4000 μF, 4500 μF, 5000 μF, 5500 μF, 6000 μF, 6500 μF, 7000 μF, 7500 μF or 8000 μF. However, it is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0036] Preferably, the magnetizing machine voltage used for magnetizing is 1000V - 2000V. For example, it can be 1000V, 1200V, 1500V, 1600V, 1800V or 2000V. However, it is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0037] As a preferred technical solution of the preparation method provided by the present invention, the preparation method includes the following steps:

[0038] (1) Mix magnetic powder, binder and auxiliary materials according to the formula amount to obtain a mixture;

[0039] (2) Knead the mixture described in step (1) under the conditions of a temperature of 80°C - 150°C and an absolute pressure of 2 MPa - 5 Mpa. After kneading is completed, open mill under the conditions of 50°C - 55°C;

[0040] (3) After open milling is completed, break up and homogenize the sheet material to obtain granular material with an average particle size of 8 mm - 12 mm; after crushing and dyeing, add the granular material to an extruder for extrusion molding; the temperature for extrusion molding is 50°C - 130°C, and the extrusion speed is 200 r / min - 500 r / min;

[0041] (4) Use a magnetizing machine with a capacitor of 4000 μF - 8000 μF and a voltage of 1000V - 2000V for magnetizing to obtain the magnet for the anti-theft label.

[0042] The numerical ranges described in the present invention include not only the above-listed point values, but also any point values between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the ranges.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] The first magnetic powder used in the present invention has the characteristic of high coercivity, providing a relatively high coercivity for the magnet of the anti-theft label; the second magnetic powder used in the present invention has a low cost and a wide source. By mixing with the first magnetic powder, the obtained magnet for the anti-theft label can have a remanence of 170 mT - 185 mT and a coercivity of 420 kA / m - 450 kA / m, is easy to be demagnetized and not easily interfered, and can achieve the purpose of preventing card skimming. Detailed implementation manners

[0045] The technical solution of the present invention will be further described below through specific implementation manners. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0046] Example 1

[0047] This example provides a magnet for anti-theft labels. In terms of mass percentage, the preparation raw materials of the magnet for anti-theft labels include 85 wt% of magnetic powder, 13 wt% of binder, and 2 wt% of auxiliary materials.

[0048] The magnetic powder includes samarium iron nitride magnetic powder and iron powder with a mass ratio of 1:1. Among them, the remanence of the used samarium iron nitride magnetic powder is 380 mT, and the coercivity is 920 kA / m.

[0049] The binder is chlorinated polyethylene (Hangzhou Keli, CM301).

[0050] The auxiliary materials include stearic acid, calcium stearate, coupling agent (aluminate coupling agent, DL-411D), and plasticizer (epoxidized soybean oil, XPJ006) with a mass ratio of 1:1:1:1

[0051] The preparation method of the magnet for anti-theft labels provided in this example includes the following steps:

[0052] (1) Mix the magnetic powder, binder, and auxiliary materials according to the formula amount to obtain a mixed material;

[0053] (2) Knead the mixed material obtained in step (1) under the conditions of a temperature of 125 °C and an absolute pressure of 2 Mpa. After the kneading is completed, open mill three times under the condition of 55 °C;

[0054] (3) After the open milling is completed, disperse, crush, and homogenize the sheet material to obtain granular material with an average particle size of 10 mm; after crushing and dyeing, add the granular material to an extruder for extrusion molding; the first temperature for extrusion molding is 50 °C, the second temperature is 100 °C, the third temperature is 110 °C, the extrusion speed is 200 r / min, the cross-sectional size of the extrusion is 30 mm × 0.45 mm, and then cut into magnetic strips of 30 mm × 10 mm × 0.45 mm;

[0055] (4) Use a magnetizer with a capacitance of 4000 μF and a voltage of 1000 V to magnetize to obtain the magnet for anti-theft labels.

[0056] Example 2

[0057] This embodiment provides a magnet for anti-theft labels. In terms of mass percentage, the raw materials for preparing the magnet for anti-theft labels include 70 wt% of magnetic powder, 28 wt% of binder, and 2 wt% of auxiliary materials.

[0058] The magnetic powder includes samarium-iron-nitrogen magnetic powder and iron powder with a mass ratio of 1.5:1. Among them, the remanence of the used samarium-iron-nitrogen magnetic powder is 350 mT, and the coercivity is 880 kA / m.

[0059] The binder is chlorinated polyethylene (Hangzhou Keli, CM301).

[0060] The auxiliary materials include stearic acid, calcium stearate, coupling agent (aluminate coupling agent, DL-411D), and plasticizer (epoxidized soybean oil, XPJ006) with a mass ratio of 1:1:1:1.

[0061] The preparation method of the magnet for anti-theft labels provided by this embodiment includes the following steps:

[0062] (1) Mix the magnetic powder, binder, and auxiliary materials according to the formula amount to obtain a mixed material;

[0063] (2) Carry out internal mixing on the mixed material described in step (1) under the conditions of a temperature of 80 °C and an absolute pressure of 5 MPa. After the internal mixing is completed, carry out open mixing three times under the condition of 50 °C;

[0064] (3) After the open mixing is completed, disperse, crush, and homogenize the sheet material to obtain particulate material with an average particle size of 10 mm; after crushing and dyeing, add the particulate material to an extruder for extrusion molding; the first temperature for extrusion molding is 60 °C, the second temperature is 95 °C, the third temperature is 130 °C, the extrusion speed is 500 r / min, the cross-sectional size of the extrusion is 30 mm × 0.45 mm, and then cut it into magnetic strips with a size of 30 mm × 10 mm × 0.45 mm;

[0065] (4) Use a magnetizer with a capacitance of 4000 μF and a voltage of 1000 V to magnetize to obtain the magnet for anti-theft labels.

[0066] Comparative Example 1

[0067] This comparative example provides a magnet for anti-theft labels. In terms of mass percentage, the raw materials for preparing the magnet for anti-theft labels include 85 wt% of magnetic powder, 13 wt% of binder, and 2 wt% of auxiliary materials.

[0068] The magnetic powder includes neodymium-iron-boron magnetic powder and strontium ferrite powder with a mass ratio of 2.4:1. Among them, the remanence of the used neodymium-iron-boron magnetic powder is 720 mT, and the coercivity is 600 kA / m; the remanence of the used strontium ferrite powder is 260 mT, and the coercivity is 290 kA / m.

[0069] The binder is chlorinated polyethylene (Hangzhou Keli, CM301).

[0070] The auxiliary materials include stearic acid, calcium stearate, coupling agent (aluminate coupling agent, DL-411D), and plasticizer (epoxidized soybean oil, XPJ006) with a mass ratio of 1:1:1:1.

[0071] The preparation method of the magnet for anti-theft label provided by this comparative example includes the following steps:

[0072] (1) Mix magnetic powder, binder, and auxiliary materials according to the formula amounts to obtain a mixed material;

[0073] (2) Knead the mixed material obtained in step (1) under the conditions of a temperature of 125°C and an absolute pressure of 2 Mpa. After kneading is completed, open mill three times under the condition of 55°C;

[0074] (3) After open milling is completed, disperse, crush, and homogenize the sheet material to obtain granular material with an average particle size of 10 mm; after crushing and dyeing, add the granular material to an extruder for extrusion molding; the first temperature for extrusion molding is 50°C, the second temperature is 100°C, the third temperature is 110°C, the extrusion speed is 200 r / min, the cross-sectional size of the extrusion is 30 mm × 0.45 mm, and then cut into magnetic strips of 30 mm × 10 mm × 0.45 mm;

[0075] (4) Use a magnetizer with a capacitance of 4000 μF and a voltage of 1000 V to magnetize to obtain the magnet for anti-theft label.

[0076] Comparative Example 2

[0077] This comparative example provides a magnet for anti-theft label. In terms of mass percentage, the raw materials for preparing the magnet for anti-theft label include 85 wt% of magnetic powder, 13 wt% of binder, and 2 wt% of auxiliary materials.

[0078] The magnetic powder includes neodymium iron boron magnetic powder and strontium ferrite powder with a mass ratio of 1.5:1. Among them, the remanence of the used neodymium iron boron magnetic powder is 720 mT, and the coercivity is 600 KA / m; the remanence of the used strontium ferrite powder is 260 mT, and the coercivity is 290 KA / m.

[0079] The binder is chlorinated polyethylene (Hangzhou Keli, CM301).

[0080] The auxiliary materials include stearic acid, calcium stearate, coupling agent (aluminate coupling agent, DL-411D), and plasticizer (epoxidized soybean oil, XPJ006) with a mass ratio of 1:1:1:1.

[0081] The preparation method of the magnet for anti-theft label provided by this comparative example includes the following steps:

[0082] (1) Mix the magnetic powder, binder and auxiliary materials according to the formula amount to obtain a mixture;

[0083] (2) Knead the mixture described in step (1) under the conditions of a temperature of 125 °C and an absolute pressure of 2 Mpa. After the kneading is completed, open mill three times under the condition of 55 °C;

[0084] (3) After the open milling is completed, break up, crush and homogenize the sheet material to obtain granular material with an average particle size of 10 mm; after crushing and dyeing, add the granular material to an extruder for extrusion molding; the first temperature for extrusion molding is 50 °C, the second temperature is 100 °C, the third temperature is 110 °C, the extrusion speed is 200 r / min, the cross-sectional size of the extrusion is 30 mm × 0.45 mm, and then cut it into magnetic strips of 30 mm × 10 mm × 0.45 mm;

[0085] (4) Use a magnetizer with a capacitance of 4000 μF and a voltage of 1000 V for magnetization to obtain the magnet for the anti-theft label.

[0086] Comparative Example 3

[0087] This comparative example provides a magnet for an anti-theft label. In terms of mass percentage, the raw materials for preparing the magnet for the anti-theft label include 85 wt% of magnetic powder, 13 wt% of binder and 2 wt% of auxiliary materials.

[0088] The magnetic powder includes samarium-iron-nitrogen magnetic powder and strontium ferrite powder with a mass ratio of 2.4:1. Among them, the remanence of the used samarium-iron-nitrogen magnetic powder is 380 mT, and the coercivity is 920 kA / m; the remanence of the used strontium ferrite powder is 260 mT, and the coercivity is 290 kA / m.

[0089] The binder is chlorinated polyethylene (Hangzhou Keli, CM301).

[0090] The auxiliary materials include stearic acid, calcium stearate, coupling agent (aluminate coupling agent, DL-411D) and plasticizer (epoxidized soybean oil, XPJ006) with a mass ratio of 1:1:1:1.

[0091] The preparation method of the magnet for the anti-theft label provided by this comparative example includes the following steps:

[0092] (1) Mix the magnetic powder, binder and auxiliary materials according to the formula amount to obtain a mixture;

[0093] (2) Knead the mixture described in step (1) under the conditions of a temperature of 125 °C and an absolute pressure of 2 Mpa. After the kneading is completed, open mill three times under the condition of 55 °C;

[0094] After the open mill process is completed, the sheet material is broken up, crushed, and homogenized to obtain granular material with an average particle size of 10 mm. After crushing and dyeing, the granular material is added to an extruder for extrusion molding. The first temperature for extrusion molding is 50°C, the second temperature is 100°C, the third temperature is 110°C, the extrusion speed is 200 r / min, the cross-sectional size of the extrusion is 30 mm × 0.45 mm, and then it is cut into magnetic strips with dimensions of 30 mm × 10 mm × 0.45 mm.

[0095] (4)Magnetization is carried out using a magnetizer with a capacitance of 4000 μF and a voltage of 1000 V to obtain the magnet for the anti-theft label.

[0096] Comparative Example 4

[0097] This comparative example provides a magnet for an anti-theft label. In terms of mass percentage, the raw materials for preparing the magnet for the anti-theft label include 85 wt% of magnetic powder, 13 wt% of binder, and 2 wt% of auxiliary materials.

[0098] The magnetic powder includes samarium iron nitride magnetic powder and strontium ferrite powder with a mass ratio of 1.5:1. Among them, the remanence of the used samarium iron nitride magnetic powder is 380 mT, and the coercivity is 920 kA / m; the remanence of the used strontium ferrite powder is 260 mT, and the coercivity is 290 kA / m.

[0099] The binder is chlorinated polyethylene (Hangzhou Keli, CM301).

[0100] The auxiliary materials include stearic acid, calcium stearate, coupling agent (aluminate coupling agent, DL-411D), and plasticizer (epoxidized soybean oil, XPJ006) with a mass ratio of 1:1:1:1.

[0101] The preparation method of the magnet for the anti-theft label provided in this comparative example includes the following steps:

[0102] (1)Mix the magnetic powder, binder, and auxiliary materials according to the formula amounts to obtain a mixed material;

[0103] (2)Carry out internal mixing on the mixed material described in step (1) under the conditions of a temperature of 125°C and an absolute pressure of 2 Mpa. After the internal mixing is completed, carry out open mill three times under the condition of 55°C.

[0104] (3)After the open mill process is completed, the sheet material is broken up, crushed, and homogenized to obtain granular material with an average particle size of 10 mm. After crushing and dyeing, the granular material is added to an extruder for extrusion molding. The first temperature for extrusion molding is 50°C, the second temperature is 100°C, the third temperature is 110°C, the extrusion speed is 200 r / min, the cross-sectional size of the extrusion is 30 mm × 0.45 mm, and then it is cut into magnetic strips with dimensions of 30 mm × 10 mm × 0.45 mm.

[0105] (4) Magnetize using a magnetizer with a capacitance of 4000 μF and a voltage of 1000 V to obtain the magnet for the anti-theft label.

[0106] Comparative Example 5

[0107] This comparative example provides a magnet for an anti-theft label. In terms of mass percentage, the raw materials for preparing the magnet for the anti-theft label include 85 wt% of magnetic powder, 13 wt% of binder, and 2 wt% of auxiliary materials.

[0108] The magnetic powder includes samarium-iron-nitrogen magnetic powder and strontium ferrite powder with a mass ratio of 1:1. Among them, the remanence of the used samarium-iron-nitrogen magnetic powder is 380 mT, and the coercivity is 920 kA / m; the remanence of the used strontium ferrite powder is 260 mT, and the coercivity is 290 kA / m.

[0109] The binder is chlorinated polyethylene (Hangzhou Keli, CM301).

[0110] The auxiliary materials include stearic acid, calcium stearate, coupling agent (aluminate coupling agent, DL-411D), and plasticizer (epoxy soybean oil, XPJ006) with a mass ratio of 1:1:1:1.

[0111] The preparation method of the magnet for the anti-theft label provided in this comparative example includes the following steps:

[0112] (1) Mix the magnetic powder, binder, and auxiliary materials according to the formula amount to obtain a mixture.

[0113] (2) Knead the mixture obtained in step (1) under the conditions of a temperature of 125 °C and an absolute pressure of 2 MPa. After kneading is completed, open mill three times under the condition of 55 °C.

[0114] (3) After open milling is completed, break up, crush, and homogenize the sheet material to obtain particulate material with an average particle size of 10 mm; after crushing and dyeing, add the particulate material to an extruder for extrusion molding; the first temperature for extrusion molding is 50 °C, the second temperature is 100 °C, the third temperature is 110 °C, the extrusion speed is 200 r / min, the cross-sectional size of the extrusion is 30 mm × 0.45 mm, and then cut into magnetic strips of 30 mm × 10 mm × 0.45 mm.

[0115] (4) Magnetize using a magnetizer with a capacitance of 4000 μF and a voltage of 1000 V to obtain the magnet for the anti-theft label.

[0116] Comparative Example 6

[0117] This comparative example provides a magnet for an anti-theft label. In terms of mass percentage, the raw materials for preparing the magnet for the anti-theft label include 85 wt% of magnetic powder, 13 wt% of binder, and 2 wt% of auxiliary materials.

[0118] The magnetic powder is neodymium iron boron magnetic powder. Among them, the remanence of the neodymium iron boron magnetic powder used is 720 mT, and the coercivity is 600 kA / m.

[0119] The binder is chlorinated polyethylene (Hangzhou Keli, CM301).

[0120] The auxiliary materials include stearic acid, calcium stearate, coupling agent (aluminate coupling agent, DL-411D) and plasticizer (epoxidized soybean oil, XPJ006) with a mass ratio of 1:1:1:1.

[0121] The preparation method of the magnet for anti-theft label provided by this comparative example includes the following steps:

[0122] (1) Mix the magnetic powder, binder and auxiliary materials according to the formula amount to obtain a mixture.

[0123] (2) Knead the mixture described in step (1) under the conditions of a temperature of 125 °C and an absolute pressure of 2 MPa. After the kneading is completed, open mill three times under the condition of 55 °C.

[0124] (3) After the open milling is completed, break up and homogenize the sheet material to obtain particulate material with an average particle size of 10 mm; after the breaking and dyeing, add the particulate material to an extruder for extrusion molding; the first temperature for extrusion molding is 50 °C, the second temperature is 100 °C, the third temperature is 110 °C, the extrusion speed is 200 r / min, the cross-sectional size of the extrusion is 30 mm × 0.45 mm, and then cut into magnetic strips of 30 mm × 10 mm × 0.45 mm.

[0125] (4) Use a magnetizer with a capacitance of 4000 μF and a voltage of 1000 V to magnetize to obtain the magnet for anti-theft label.

[0126] Comparative Example 7

[0127] This comparative example provides a magnet for anti-theft label, which is the same as Example 1 except that the magnetic powder is a samarium iron nitride magnetic powder and iron powder with a mass ratio of 0.8:1.

[0128] Comparative Example 8

[0129] This comparative example provides a magnet for anti-theft label, which is the same as Example 1 except that the magnetic powder is a samarium iron nitride magnetic powder and iron powder with a mass ratio of 2.7:1.

[0130] Comparative Example 9

[0131] This comparative example provides a magnet for anti-theft label. In terms of mass percentage, the raw materials for preparing the magnet for anti-theft label include 96 wt% of magnetic powder, 2 wt% of binder and 2 wt% of auxiliary materials.

[0132] The magnetic powder includes samarium-iron-nitrogen magnetic powder and iron powder with a mass ratio of 2.4:1. Among them, the remanence of the used samarium-iron-nitrogen magnetic powder is 400 mT, and the coercivity is 960 kA / m.

[0133] The binder is chlorinated polyethylene (Hangzhou Keli, CM301).

[0134] The auxiliary materials include stearic acid, calcium stearate, coupling agent (aluminate coupling agent, DL-411D) and plasticizer (epoxidized soybean oil, XPJ006) with a mass ratio of 1:1:1:1.

[0135] The preparation method of the magnet for anti-theft label provided by this comparative example includes the following steps:

[0136] (1) Mix the magnetic powder, binder and auxiliary materials according to the formula amount to obtain a mixture.

[0137] (2) Knead the mixture described in step (1) under the conditions of a temperature of 180 °C and an absolute pressure of 0.3 Mpa. After the kneading is completed, open mill three times under the condition of 60 °C.

[0138] (3) After the open milling is completed, break up, crush and homogenize the sheet material to obtain particulate material with an average particle size of 10 mm; after the crushing and dyeing, add the particulate material to an extruder for extrusion molding; the first temperature for extrusion molding is 80 °C, the second temperature is 105 °C, the third temperature is 150 °C, the extrusion speed is 1000 r / min, the cross-sectional size of the extrusion is 30 mm × 0.45 mm, and then cut into magnetic strips of 30 mm × 10 mm × 0.45 mm.

[0139] (4) Use a magnetizer with a capacitance of 4000 μF and a voltage of 1000 V for magnetization to obtain the magnet for anti-theft label.

[0140] Comparative Example 10

[0141] This comparative example provides a magnet for anti-theft label, which is the same as Example 1 except that the samarium-iron-nitrogen magnetic powder in Comparative Example 1 is replaced with neodymium-iron-boron magnetic powder with a remanence of 720 mT and a coercivity of 600 kA / m.

[0142] Comparative Example 11

[0143] This comparative example provides a magnet for anti-theft label, which is the same as Example 1 except that the samarium-iron-nitrogen magnetic powder in Comparative Example 1 is replaced with neodymium-iron-boron magnetic powder with a remanence of 700 mT and a coercivity of 560 kA / m.

[0144] Comparative Example 12

[0145] This comparative example provides a magnet for anti-theft tags. Except that the samarium-iron-nitrogen magnetic powder in Comparative Example 1 is replaced with neodymium-iron-boron magnetic powder having a remanence of 750 mT and a coercivity of 640 kA / m, the rest are the same as in Example 1.

[0146] Performance Test

[0147] The remanence and coercivity of the magnets for anti-theft tags obtained in the above examples and comparative examples were tested, and the results are shown in Table 1.

[0148] When the magnet has appropriate remanence and coercivity, it has the properties of being easily demagnetized and not easily interfered with, is not easily stolen and swiped, and is suitable for anti-theft tags; when the magnet has a relatively too high remanence, it is likely to cause difficulty in demagnetization. Further, when there is a relatively too high coercivity at the same time, it will also cause inability to demagnetize; when it is difficult to demagnetize or unable to demagnetize, it is not suitable for the magnet for anti-theft tags. In addition, when the magnet has a relatively too low remanence and a relatively too low coercivity, when tested with N35 neodymium-iron-boron strong magnetic interference, it shows an extremely easy-to-be-interfered situation, and there is a risk of being easily stolen and swiped; while when the magnet has a relatively too high remanence and a relatively too high coercivity, when tested with N35 neodymium-iron-boron strong magnetic interference, it shows a situation of not being easily interfered with, but at the same time it is also difficult to demagnetize, and it is also not suitable for the magnet for anti-theft tags.

[0149] Table 1

[0150]

[0151] In summary, the first magnetic powder used in the present invention has the characteristics of low remanence and high coercivity, providing relatively high remanence and coercivity for the magnet for anti-theft tags; although the second magnetic powder used in the present invention has relatively weak magnetic properties such as remanence and coercivity, it has good temperature stability, and the cost of the second magnetic powder is low and the source is wide, and it can also improve the processing performance of the first magnetic powder by mixing with the first magnetic powder; the magnet for anti-theft tags provided by the present invention through the synergistic cooperation of the first magnetic powder and the second magnetic powder makes the obtained magnet for anti-theft tags have low remanence and high coercivity, is not easily magnetized, and can achieve the purpose of preventing theft and swiping.

[0152] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A magnet for an anti-theft tag, characterized in that: In terms of mass percentage, the raw materials for preparing the magnet for the anti-theft label include 70wt%-85wt% of magnetic powder, ≤2wt% of auxiliary materials and the remainder of a binder; The magnetic powder includes a first magnetic powder and a second magnetic powder in a mass ratio of (1-1.5):1; The first magnetic powder is samarium iron nitrogen magnetic powder; The second magnetic powder is iron powder; The remanence of the magnet used for the anti-theft tag is 170mT-185mT, and the coercive force is 420KA / m-450KA / m.

2. The magnet for anti-theft label according to claim 1, characterized in that: The remanence of the samarium iron nitrogen magnetic powder is 350mT-380mT.

3. The magnet for anti-theft label according to claim 1 or 2, characterized in that: The coercive force of the samarium iron nitrogen magnetic powder is 880KA / m-920KA / m.

4. The magnet for anti-theft label according to claim 1, characterized in that: The adhesive includes any one of chloroprene rubber, ethylene-propylene rubber, nitrile rubber, chlorinated polyethylene, ethylene-vinyl acetate copolymer or thermoplastic elastomer, or a combination of at least two thereof.

5. The magnet for anti-theft label according to claim 1, characterized in that: The auxiliary material includes any one of stearic acid, calcium stearate, a coupling agent or a plasticizer, or a combination of at least two of them.

6. A method for preparing a magnet for an anti-theft label, characterized in that: The preparation method comprises the following steps: The magnetic powder, binder and auxiliary materials are mixed according to the formula, and then internal mixing, open mixing, extrusion molding and magnetization are carried out in sequence to obtain the magnet for the anti-theft label according to any one of claims 1 to 5.

7. The preparation method according to claim 6, characterized in that: The temperature of the banburying is 80°C-125°C; And / or, the absolute pressure of the banburying is 2MPa-5Mpa; And / or, the temperature of the open refining is 50°C-55°C.

8. The preparation method according to claim 6, characterized in that: The extrusion molding temperature is 50°C-130°C; And / or, the extrusion speed of the extrusion molding is 200r / min-500r / min.

9. The preparation method according to any one of claims 6 to 8, characterized in that: The magnetizer capacitor used in the magnetization is 4000μF-8000μF; And / or, the voltage of the magnetizer used for the magnetization is 1000V-2000V.

10. The preparation method according to claim 6, characterized in that: The preparation method comprises the following steps: (1) Mixing magnetic powder, binder and auxiliary materials according to the formula to obtain a mixture; (2) kneading the mixture of step (1) at a temperature of 80°C-125°C and an absolute pressure of 2MPa-5Mpa, and after kneading, refining at 50°C-55°C; (3) After the refining is completed, the flake material is broken up, crushed and homogenized to obtain a granular material with an average particle size of 8mm-12mm; after crushing and dyeing, the granular material is added to the extruder for extrusion molding; the extrusion molding temperature is 50℃-130℃, and the extrusion speed is 200r / min-500r / min; (4) Use a magnetizer with a capacitance of 4000 μF-8000 μF and a voltage of 1000 V-2000 V to magnetize the magnet to obtain the magnet for the anti-theft label.

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