阅读说明：本技术 一种降低abs塑料重金属含量的方法 (method for reducing heavy metal content in ABS plastics ) 是由 刘瑾 李�真 叶青霞 夏莉 王卓 吴东兴 张定仑 樊炳宇 于 2019-11-04 设计创作，主要内容包括：本发明属于工业塑料技术领域,具体涉及一种降低ABS塑料重金属含量的方法,采用区域熔炼的方法对含重金属的ABS塑料进行处理,得到重金属含量降低的ABS塑料。本发明的技术方案,将用于提纯金属的区域熔炼法引入到塑料重金属去除工艺中,实现了ABS塑料的纯化处理,没有其他试剂或化学药品参与,绿色环保,可大幅度提高废旧ABS塑料的回收再利用率。(The invention belongs to the technical field of industrial plastics, and particularly relates to methods for reducing the heavy metal content of ABS plastics.)

1, A method for reducing the heavy metal content of ABS plastics, which is characterized in that the ABS plastics containing heavy metal are treated by adopting a zone melting method to obtain the ABS plastics with reduced heavy metal content.

2. The method for reducing the heavy metal content of the ABS plastic according to claim 1, comprising the following steps:

a) processing the ABS plastic containing heavy metal into long strip-shaped sample strips;

b) heating tips of the sample strip to be molten by a heating device;

c) slowly moving the sample strip and/or the heating device to enable the heated area on the sample strip to be slowly moved to the tail end, controlling the relative moving speed of the sample strip and the heating device to ensure that the sample strip at the position of the heating device can be heated to be molten, and naturally cooling and solidifying the sample strip in the molten state after the sample strip is far away from the heating device;

d) repeating the steps b) and c) for 20-60 times, wherein the initial end of each heating in the step b) is the same as that of the previous times;

e) removing the tail end of the sample strip to obtain the ABS plastic with the reduced heavy metal content.

3. The method for reducing the heavy metal content of the ABS plastic according to claim 2, wherein the method comprises the following steps: the steps a), b) and c) are all carried out under a nitrogen atmosphere.

4. The method for reducing the heavy metal content of the ABS plastic according to claim 2, wherein the method comprises the following steps: in the step a), the heavy metal contained in the ABS plastic is lead.

5. The method for reducing the heavy metal content of the ABS plastic according to claim 2, wherein the method comprises the following steps: in the step b), the heating unit of the heating device is an annular heating sleeve.

6. The method for reducing the heavy metal content of the ABS plastic according to claim 2, wherein the method comprises the following steps: the heating temperature of the heating device is 220-300 ℃.

7. The method for reducing the heavy metal content of the ABS plastic according to claim 2, wherein the method comprises the following steps: the length of the instantaneous heating area on the sample strip is 3-7 cm.

8. The method for reducing the heavy metal content in the ABS plastic according to claim 2, wherein the tail end is removed in step e), wherein heating zone lengths are removed from the tail end of the sample strip.

9. The method for reducing the heavy metal content of the ABS plastic according to claim 2, wherein the method comprises the following steps: the relative moving speed of the heating device and the sample strip is as follows: the relative movement speed of the sample strip and the heating device is 1-2 mm/s.

Technical Field

The invention belongs to the technical field of industrial plastics, and particularly relates to methods for reducing the heavy metal content of ABS plastics.

Background

ABS plastic has excellent mechanical performance, better heat resistance and chemical resistance, and is the engineering plastic with the most application of .

With the increasing environmental protection requirement, new requirements are provided for the recycling rate of the waste plastics. However, a large amount of waste plastics are polluted in the using process, and heavy metal elements are carried after the waste plastics are recovered, so that the recycling of the plastics is hindered.

For example, ABS plastic used for packaging lead-acid storage batteries carries trace heavy metal lead during recovery, so that a large amount of ABS plastic recovered from waste batteries cannot be reused, in the prior art is generally cleaned by water or other detergents, but the method can only remove lead stained on the surface of the ABS plastic and cannot remove lead which has permeated into the plastic.

The scheme shows that when the TDI is purified by using the zone melting method, the melting zone moving speed is smaller, the purity of the sample starting end is higher, the temperature difference between a cooler and a heater is larger, the sample starting end is higher, the melting zone is larger, the number of times of zone melting is less, the vertical zone melting is better than the vertical downward zone melting effect, the number of times of zone melting is larger, the impurity removal amount is larger, and the number of times of zone melting is increased after reaching the limit.

The scheme shows that the zone melting technology is still only applied to the field of impurity removal of small-molecular-weight substrate materials, and the molecular weight of impurities is equivalent to that of the substrate. However, the molecular weight of ABS plastic is as high as tens of thousands or even hundreds of thousands, which is much larger than TDI, and the heavy metal impurity lead in the ABS plastic has a molecular weight of only 207.3, and the heavy metal impurity in the ABS plastic with large molecular weight is removed by a zone melting method, so the TDI purification method is obviously not feasible by transferring. Therefore, the inventors set out a problem of how to apply the zone melting technique to engineering plastics.

Disclosure of Invention

The invention aims to provide methods for reducing the heavy metal content of ABS plastics, which can effectively reduce the heavy metal content of the ABS plastics, and have the advantages of simple equipment and simple and convenient operation.

In order to achieve the purpose, the invention adopts the technical scheme that methods for reducing the heavy metal content of the ABS plastic adopt a zone melting method to treat the ABS plastic containing heavy metal, so as to obtain the ABS plastic with reduced heavy metal content.

According to the technical scheme, the zone melting method for purifying the metal is introduced into the plastic heavy metal removal process, so that the purification treatment of the ABS plastic is realized, other reagents or chemicals are not involved, the method is green and environment-friendly, and the recycling rate of the waste ABS plastic can be greatly improved.

Specifically, the method for reducing the heavy metal content of the ABS plastic comprises the following steps:

a) processing the ABS plastic containing heavy metal into long strip-shaped sample strips;

b) heating tips of the sample strip to be molten by a heating device;

c) slowly moving the sample strip and/or the heating device to enable the heated area on the sample strip to be slowly moved to the tail end, controlling the relative moving speed of the sample strip and the heating device to ensure that the sample strip at the position of the heating device can be heated to be molten, and naturally cooling and solidifying the sample strip in the molten state after the sample strip is far away from the heating device;

d) repeating the steps b) and c) for 20-60 times, wherein the initial end of each heating in the step b) is the same as that of the previous times;

e) removing the tail end of the sample strip to obtain the ABS plastic with the reduced heavy metal content.

Specifically, the steps a), b) and c) are all carried out under a nitrogen atmosphere. If ABS plastic is melted in air and exposed to oxygen, molecules of the ABS plastic are oxidized and decomposed.

In the step a), the heavy metal contained in the ABS plastic is lead. The primary purpose of the invention is to reduce the lead content in the recycled waste battery packaging material by using a zone melting method, and after the technology is mature, the technology can be used for removing other impurities by using other engineering plastics.

In the step b), the heating unit of the heating device is an annular heating sleeve. The ABS plastic sample strip can be heated more uniformly.

The heating temperature of the heating device is 220-300 ℃. The ABS can be ensured to be heated to a molten state without decomposition.

The length of the instantaneous heating area on the sample strip is 3-7 cm. The heating area is too short, namely the melting zone is too short, so that the migration of impurity lead in the molten ABS macromolecule gap is not facilitated, and the heating area is too long, namely the melting zone is too long, so that the migration direction of the impurity lead in the melt away from the condensation interface part is difficult to control.

And in the step e), the tail end is removed, wherein the length of heating areas is removed from the tail end of the sample strip, the removed tail end has high heavy metal content, the sample can be prepared by a system after collection, and the waste ABS plastic is purified by adopting the method disclosed by the invention, so that the reutilization rate of the waste ABS plastic is improved.

The relative moving speed of the heating device and the sample strip is as follows: the relative movement speed of the sample strip and the heating device is 1-2 mm/s. Because the ABS plastic has a slow heat transfer rate, the ABS plastic is not easy to melt due to an excessively high moving speed; and the moving speed is too slow, the lead ions have insufficient migration tendency to the tail end along with the melting area of the ABS, and can be homogenized again in the melting area and difficultly concentrated to the tail end.

The beneficial effect that adopts above-mentioned technical scheme to produce lies in: the technical scheme of the invention is simple and environment-friendly, has short time and easily controlled process conditions; more importantly, the zone melting purification technology is applied to the field of heavy metal removal of high polymers, and a new research direction is provided for the field of impurity removal of engineering plastics.

Drawings

FIG. 1 is a DSC plot of ABS before and after zone melting;

FIG. 2 is an infrared spectrum of ABS before and after zone melting.

Detailed Description

The technical solution of the present invention is further described in with reference to the following examples.

The instrument comprises the following steps: the automatic slide rail (adjustable speed) of the water bottle, a heating device (with a heating ring and the width of 3cm, 5cm and 7cm), a glass tube (with the length of 120cm and the diameter of 1.2cm), a nitrogen bottle and a clamp.

Splines: taking ABS plastic recovered from waste batteries, cleaning, drying, crushing, uniformly mixing, measuring the initial lead content by ICP (inductively coupled plasma) to be 540ppm, and extruding by an extruder to prepare a plurality of sample strips with the length of about 1m and the diameter of 0.5cm respectively for later use.