CN115609786A

CN115609786A - Plastic odor removing method

Info

Publication number: CN115609786A
Application number: CN202211513320.8A
Authority: CN
Inventors: 李建军; 李凡; 汪建; 陈平绪; 叶南飚; 李聪; 彭智
Original assignee: Jiangsu Jinfa Renewable Resources Co ltd; Jinfa Environmental Protection Technology Co ltd; Kingfa Science and Technology Co Ltd; Guangdong Kingfa Science and Technology Co Ltd
Current assignee: Jiangsu Jinfa Renewable Resources Co ltd; Jinfa Environmental Protection Technology Co ltd; Kingfa Science and Technology Co Ltd; Guangdong Kingfa Science and Technology Co Ltd
Priority date: 2022-11-30
Filing date: 2022-11-30
Publication date: 2023-01-17

Abstract

The invention provides a method for removing odor of plastic, belonging to the technical field of plastic processing. The method for deodorizing the plastic comprises the following steps: under the condition of vacuumizing, performing mid-infrared heating treatment on plastic particles to be treated to obtain odor-removing plastic; the middle infrared heating uses a middle infrared ray with the wavelength of 2.5 to 6 mu m; the temperature of the mid-infrared heating is 100 to 120 ℃, and the time is 5 to 8h. Through the means of middle infrared heating, with the middle infrared ray of specific wavelength, heat treatment to the plastics, combine the evacuation to the smell of high-efficient removal plastics, reduce the smell grade of plastics.

Description

Plastic odor removing method

Technical Field

The invention relates to the technical field of plastic processing, in particular to a method for removing odor of plastic.

Background

Plastics have been widely used in agriculture, industry, traffic, packaging, construction, medical supplies, national defense industry, daily life and other fields, and as environmental protection is enhanced, recycling of waste plastics is more and more important. However, the recycled waste plastics are often accompanied with large peculiar smell, so that the deodorization of the plastics is an urgent problem to be solved.

The current methods for deodorizing plastics are mainly by drying and steaming. For example, the prior art discloses a low-emission and low-odor filling functional master batch and a preparation method thereof, and the low-emission and low-odor plastic master batch is prepared in a multi-stage vacuum and hot air circulation mode; also prior art discloses deodorizing waste plastics crushed into small particles by steam distillation. However, in the drying and steaming process, the temperature rising speed of the waste plastics is slow, and the external temperature is higher than the internal temperature, which is not beneficial to the diffusion of small molecular substances, so that the odor grade of the waste plastics cannot be quickly and effectively reduced.

Therefore, it is desirable to provide a method for deodorizing plastic, which can rapidly and effectively remove the odor in the plastic and reduce the odor level of the plastic.

Disclosure of Invention

The invention aims to overcome the defect of poor odor removal effect of plastics in the prior art, and provides a method for removing odor of plastics, which can efficiently remove the odor of plastics and reduce the odor grade by means of combining mid-infrared heating and vacuumizing.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for deodorizing plastic comprises the following steps:

under the condition of vacuumizing, carrying out mid-infrared heating treatment on plastic particles to be treated to obtain odor-removing plastic;

the middle infrared heating uses a middle infrared ray with the wavelength of 2.5 to 6 mu m; the temperature of the mid-infrared heating is 100 to 120 ℃, and the time is 5 to 8h.

The invention adopts the mid-infrared heating and combines the vacuumizing means, effectively removes the smell of the plastic in a short time, reduces the smell grade of the plastic and does not cause the degradation of the performance of the plastic.

The middle infrared heating heats the inside and the outside of the plastic simultaneously mainly through molecular thermal motion, and the inside and the outside have no temperature difference, thereby being beneficial to the diffusion of small molecules inside plastic particles; and the medium infrared heating is used as a heat radiation type heating mode, a transfer medium is not needed, and the heat effect is good.

The odor substances in the plastic mainly comprise small molecules such as acetic acid, dipentene, hexanal, nonanal, 2-ethyl hexanol and the like. The inventor researches and discovers that the frequency of the medium infrared ray with the wavelength of 2.5 to 6 mu m is close to the transition thermal motion frequency of the molecular vibration energy level of the odor substance in the plastic, the heat effect of the medium infrared ray is obvious, the heating rate is high, the emission rate of the odor substance in the plastic is very high by performing medium infrared heating treatment on the plastic, and the odor removing efficiency is very high. By means of cooperation with the vacuumizing, odor substances in the plastic particles to be treated are immediately vacuumized and removed after being emitted, and the odor removal effect on the plastic is further improved.

Compared with infrared rays with other wavelengths, the middle infrared rays have certain selectivity on heating and emission of odor substances in the plastic, and the performance of the plastic cannot be damaged. The inventor researches and discovers that the effect of heating the plastic by adopting near infrared rays or far infrared rays is far less than that of using medium infrared rays with the wavelength of 2.5 to 6 mu m, although the smell of the plastic can be emitted to a certain degree; in addition, the near infrared rays or far infrared rays can also cause the degradation of the performance of the plastic, and limit the subsequent application of the plastic.

For the temperature and time of the intermediate infrared heating treatment, the inventor researches and discovers that the odor in the plastic is not thoroughly emitted and the odor grade is still too high when the temperature is too low or the time is too short; when the temperature is too high, the plastic is easy to soften, adhere and agglomerate, so that the subsequent use of the plastic is influenced, and odor substances in the plastic are prevented from being diffused due to the agglomeration of the plastic, so that the plastic subjected to the intermediate infrared heating treatment still has too high odor grade; over time, plastics are susceptible to performance degradation, such as a substantial drop in melt flow rate.

Preferably, the wavelength of the mid-infrared ray is 4 to 5 μm.

The frequency of the medium infrared ray with the wavelength of 4 to 5 mu m is closer to the transition thermal motion frequency of the molecular vibration energy level of the odor substance in the plastic, the heating selectivity of the odor substance in the plastic is higher, and the odor of the plastic can be removed more effectively.

Preferably, the temperature of the intermediate infrared heating is 100 to 110 ℃.

Preferably, the time of the intermediate infrared heating is 6 to 7 hours.

For plastics, odor ratings of 4.5 or less are generally required, and for some more stringent applications, odor ratings of 4.0 or less are required. For the intermediate infrared heating treatment, when the temperature is 100 to 110 ℃ and the time is 6 to 7 hours, the requirements can be met, the temperature is further increased, the time is prolonged, and the reduction effect on the odor grade is not obvious.

Preferably, the power of the intermediate infrared heating is 50 to 400kW.

More preferably, the power of the mid-infrared heating is 100 to 300 kW.

The acceleration rate is influenced by the power of the mid-infrared heating, the heating rate is proper within the power range of 100 to 300kW, and the odor removing effect on the plastic is excellent. When the power is less than 100kW, the heating rate is too slow, so that the odor removal effect of the plastic is poor on one hand, and the performance of the plastic is deteriorated after the plastic is used for a long time in a high-temperature environment on the other hand. When the power is more than 300kW, the energy consumption is overlarge, and a better effect cannot be brought to the odor removal of the plastic.

Preferably, the vacuum pumping condition is that the vacuum degree is controlled to be less than or equal to 100Pa.

More preferably, the vacuum degree is controlled to be 20 to 50 Pa under the vacuum pumping condition.

Preferably, the plastic particles are obtained by processing recycled plastics.

The recycled plastic may be at least one of recycled polypropylene (PP), polyethylene (PE), polystyrene (PS), polycarbonate (PC), and Polyamide (PA).

Preferably, the average particle size of the plastic particles is 0.5 to 2mm.

More preferably, the average particle diameter of the plastic particles is 1 to 1.5 mm.

The odor removal is carried out on the plastic particles with proper average particle size, the odor removal rate is higher, and the odor removal effect is better. And the plastic obtained after deodorization is still in a granular shape and can be directly used for subsequent further processing.

Preferably, the plastic particles are continuously stirred during the mid-infrared heat treatment.

The continuous stirring of the plastic particles is beneficial to better odor emission effect, and agglomeration and adhesion among the plastic particles are avoided.

According to the method for deodorizing the plastic, the ratio of the melt flow rate of the obtained deodorized plastic to the melt flow rate of the plastic particles to be treated is less than or equal to 1.1.

The closer the ratio of melt flow rate of the deodorized plastic to the plastic particles to be treated is to 1, the more slightly the molecular chain of the plastic is broken, the less the plastic changes its properties after deodorization. When the ratio of the melt flow rate of the deodorized plastic to the plastic particles to be treated is less than or equal to 1.1, the subsequent use of the deodorized plastic is not influenced.

Compared with the prior art, the invention has the beneficial effects that:

the invention develops a method for removing odor of plastic, which is characterized in that the plastic is heated for 5 to 8h at the temperature of 100 to 120 ℃ by a medium infrared ray with a specific wavelength through a medium infrared heating means, and the plastic is vacuumized, so that the odor of the plastic is efficiently removed, and the odor grade of the plastic is reduced.

The middle infrared heating heats the inside and the outside of the plastic simultaneously mainly through molecular thermal motion, and the inside and the outside have no temperature difference, thereby being beneficial to the diffusion of small molecules inside plastic particles; and the mid-infrared heating is used as a heat radiation type heating mode, a transfer medium is not needed, and the heat effect is good.

The frequency of the middle infrared ray with the wavelength of 2.5 to 6 mu m is close to the transition thermal motion frequency of the molecular vibration energy level of the odor substance in the plastic, the heat effect of the middle infrared ray is obvious, the heating rate is high, the middle infrared ray is subjected to middle infrared heating treatment, the emission rate of the odor substance in the plastic is very high, and the odor removing efficiency is very high.

Detailed Description

The present invention will be further described with reference to specific examples for better illustrating the objects, technical solutions and advantages of the present invention, but the examples are not intended to limit the present invention in any way.

The wavelength and power of the intermediate infrared heating device, the near infrared heating device or the far infrared heating device used in the embodiments and the comparative examples of the invention are adjusted by controlling the device voltage adjusting system (i.e. controlling the infrared lamp tube), or by replacing the infrared lamp tube with different wavelength.

Recycled plastic-1, which is PP recycled plastic taken from outer barrel particles of a waste washing machine, has an original odor grade of 6, and a melt flow rate of 30 g/10min at 230 ℃ and under the condition of 2.16 kg;

recycling plastic-2, which is taken from waste lunch box particles and is PP recycling plastic, wherein the original odor grade is 6, and the melt flow rate under the conditions of 230 ℃ and 2.16kg is 50 g/10min;

reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated. Unless otherwise indicated, reagents and materials used in the present invention are commercially available.

Example 1

This example provides a method for deodorizing a plastic, comprising the steps of:

crushing the recycled plastic-1 into plastic particles with the average particle size of 1mm, adding the plastic particles into a medium infrared heating device, heating by adopting medium infrared rays with the wavelength of 4-5 mu m under the conditions of vacuum pumping and the vacuum degree of 50 Pa, wherein the temperature is 100 ℃, the time is 5 hours, the power of the medium infrared heating is 200 kW, and the plastic particles are continuously stirred in the medium infrared heating process; after cooling, the deodorized plastic is obtained.

Example 2

This example provides a method of deodorising plastics which differs from example 1 in that:

the temperature of the heat treatment was 110 ℃.

Example 3

This example provides a method of deodorising a plastics material which differs from example 1 in that:

the temperature of the heat treatment was 120 ℃.

Example 4

the time of the heat treatment was 6 hours.

Example 5

the time of the heat treatment was 7 hours.

Example 6

the time of the heat treatment was 8 hours.

Example 7

heating the mixture by using a medium infrared ray with the wavelength of 2.5 to 3 mu m.

Example 8

heating the mixture by using a medium infrared ray with the wavelength of 3 to 4 mu m.

Example 9

heating the mixture by using a medium infrared ray with the wavelength of 5 to 6 mu m.

Example 10

the power of the mid-infrared heating is 50 kW.

Example 11

the power of the mid-infrared heating is 100 kW.

Example 12

the power of the mid-infrared heating is 300 kW.

Example 13

the power of the mid-infrared heating is 400kW.

Example 14

the mean particle diameter of the plastic granules was 2mm.

Example 15

the mean particle diameter of the plastic granules was 4mm.

Example 16

This example provides a method of deodorizing a material, which differs from example 1 in that:

the used plastic is recycled plastic-2, and the vacuum degree is controlled to be 20Pa.

Comparative example 1

The comparative example provides a method for deodorizing plastic, which is a heating and drying method and comprises the following steps:

crushing the recycled plastic-1 into plastic particles with the average particle size of 1mm, placing the plastic particles in a dryer, heating the plastic particles at 100 ℃ for 5 hours under the condition of vacuumizing and the vacuum degree of 50 Pa, and cooling to obtain the deodorized plastic.

Comparative example 2

crushing the recycled plastic-1 into plastic particles with the average particle size of 1mm, placing the plastic particles in a dryer, heating the plastic particles at 100 ℃ for 20 hours under the condition of vacuumizing and the vacuum degree of 50 Pa, and cooling to obtain the deodorized plastic.

Comparative example 3

The comparative example provides a method for deodorizing a plastic by steaming, comprising the steps of:

and (3) crushing the recycled plastic-1 into plastic particles with the average particle size of 1mm, placing the plastic particles into a steam tank, carrying out steam treatment at 100 ℃ for 5 hours, and cooling to obtain the deodorized plastic.

Comparative example 4

and (3) crushing the recycled plastic-1 into plastic particles with the average particle size of 1mm, placing the plastic particles into a steam tank, carrying out steam treatment at 100 ℃ for 20 hours, and cooling to obtain the deodorized plastic.

Comparative example 5

This comparative example provides a method of deodorising a plastics material which differs from example 1 in that:

heating treatment is carried out by using near infrared rays with the wavelength of 0.71 to 1 mu m.

Comparative example 6

heating treatment is carried out by adopting near infrared rays with the wavelength of 1 to 2 mu m.

Comparative example 7

heating treatment is carried out by adopting far infrared rays with the wavelength of 7.5 to 14 mu m.

Comparative example 8

the time of the heat treatment was 4 hours.

Comparative example 9

This comparative example provides a method of deodorising plastics which differs from example 1 in that:

the time for the heat treatment was 9 hours.

Comparative example 10

the temperature of the heat treatment was 90 ℃.

Comparative example 11

the temperature of the heat treatment was 130 ℃.

Comparative example 12

the vacuum pumping is not carried out, and the vacuum degree is not controlled.

Performance testing

The performance of the odour-reducing plastics obtained in the above examples and comparative examples was tested by the following specific method:

odor grade: testing according to a PV3900-2000 standard method, testing 10 groups of parallel samples in total, and taking an average value; the odor grade is considered to be qualified when the odor grade is less than or equal to 4.5, and the odor grade is better when the odor grade is less than or equal to 4.0;

melt flow rate: the test was carried out at 230 ℃ under a load of 2.16kg according to GB/T3682-2000.

The test results of the examples are shown in Table 1.

TABLE 1

According to the test results in table 1, when the recycled plastic with the original odor grade of 6 is treated by the method for deodorizing plastic according to the application, the odor grade of the deodorized plastic treated in each example meets the qualified requirement, and the odor grade of the deodorized plastic treated in some examples can reach below 4.0, so that the deodorizing effect is excellent. After deodorization, the difference between the melt flow rate of the plastic and the melt flow rate of the untreated recycled plastic is less than or equal to 3 g/10min, namely, the ratio of the melt flow rate of the deodorized plastic to the melt flow rate of the plastic particles to be treated is less than or equal to 1.1.

According to examples 1 to 3 and 4 to 6, it can be seen that the odor grade of the plastic is reduced with the rise of the temperature and the extension of the time of the intermediate infrared heat treatment, but when the temperature is increased from 110 ℃ to 120 ℃ or the time is increased from 7h to 8h, the odor grade of the plastic is not changed greatly, and the melt flow rate is increased, which indicates that the molecular chains of the plastic are broken. When the temperature of the medium infrared heating is 100 to 110 ℃ and the time is 6 to 7h, the good odor removing effect can be kept, and the change of the melt flow rate of the plastic is very small. Therefore, the temperature of the medium-infrared heating is preferably 100 to 110 ℃ and the time is preferably 6 to 7h.

From example 1 and examples 7 to 9, it can be seen that the wavelength change of the mid-infrared ray has a certain influence on the odor removing effect of the plastic. The frequency of the medium infrared ray with the wavelength of 4-5 mu m is closer to the transition thermal motion frequency of the molecular vibration energy level of the odor substance in the plastic, the heating selectivity of the medium infrared ray with the wavelength of 4-5 mu m on the odor substance in the plastic is higher, the odor of the plastic can be removed more effectively, the removal effect of the medium infrared ray with the wavelength of 4-5 mu m on the odor substance in the plastic is relatively better, and the odor grade of the plastic can be effectively reduced in a shorter time. And the plastic is treated by adopting the medium infrared ray with the wavelength of 2.5 to 4 mu m or 5 to 6 mu m, so that the odor removing effect is slightly poor.

From examples 1 and 10 to 13, it can be seen that when the power of the mid-infrared heating treatment is less than 100kW, the heating rate is too slow, so that the odor removal efficiency of the plastic is low, the effect is poor, and if the low power is kept and the mid-infrared heating treatment time is prolonged, the plastic can be used in a high-temperature environment for a long time, and the performance of the plastic is deteriorated; and when the power of the intermediate infrared heating treatment is more than 300kW, the energy consumption is overlarge, and the odor grade of the plastic cannot be further optimized. Therefore, the power of the mid-infrared heating is preferably 100 to 300 kW.

From examples 14 to 16, it can be seen that the odor removal effect is better when the average particle diameter of the plastic particles is lower and the vacuum degree is lower.

The test results of the comparative examples are shown in Table 2.

TABLE 2

According to the test results of Table 2, in comparative example 1 and comparative example 3, in order to treat the recycled plastic using the drying and steaming methods, respectively, the treatment time was 5 hours, the temperature was 100 ℃, and the treatment time and temperature were the same as those of example 1. However, according to the odor rating test results, the odor rating of the odor-reducing plastic of comparative example 1 is still grade 6, and the odor rating of the odor-reducing plastic of comparative example 3 is grade 5.7, which is much higher than grade 3.8 of example 1. It shows that the odor removal effect is very poor when the plastic is treated by drying or steaming under the same temperature and time conditions.

Comparative example 2 and comparative example 4 are the treatment of the recycled plastic by drying and steaming, respectively, with a treatment time of 20h and a temperature of 100 ℃. It can be seen that although the odor grade of the deodorized plastic of comparative examples 2 and 4 is reduced compared to comparative examples 1 and 3, molecular chains of the plastic are broken due to the heating time of the process, and the melt flow rate of the plastic becomes large, which means that the plastic itself is somewhat deteriorated.

Comparative examples 5 to 7 are heating treatments using infrared rays of other wavelengths, and since the frequencies of the infrared rays of different wavelengths are different from the transition thermal motion frequency of the molecular vibrational energy level of the odorant in the plastic, the heating selectivity for the odorant in the plastic is low, and it is difficult to efficiently remove the odor of the plastic. The odour-combating plastics of comparative examples 5 to 7 had an odour rating which was too high compared to example 1.

According to the test results of comparative examples 8 to 11, when the time of the heat treatment is too short or too long and the temperature is too low or too high, the odor removing effect that the odor grade of the plastic is less than 4.5 and the change of the melt flow rate is not large is difficult to obtain. When the heating time is too long or the temperature is too high, the melt flow rate of the plastic is increased, the performance is degraded to a certain extent, and the odor removing effect is influenced due to the breakage of a plastic molecular chain part, so that the odor grade of the plastic subjected to odor removing treatment is still high.

In comparative example 12, the degree of vacuum was not controlled, i.e., vacuum pumping was not performed. Under the condition of no vacuum pumping, the odor removing effect of the plastic is not ideal, and the odor grade is only 4.9.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for deodorizing a plastic, comprising the steps of:

under the condition of vacuumizing, performing mid-infrared heating treatment on plastic particles to be treated to obtain odor-removing plastic;

the middle infrared heating uses a middle infrared ray with the wavelength of 2.5 to 6 mu m;

the temperature of the mid-infrared heating is 100 to 120 ℃, and the time is 5 to 8h.

2. The method for deodorizing plastic according to claim 1, wherein the wavelength of the mid-infrared ray is 4 to 5 μm.

3. The method for deodorizing plastic according to claim 1, wherein the temperature of the mid-infrared heating is 100 to 110 ℃.

4. The method for deodorizing plastic according to claim 1, wherein the time for the medium infrared heating is 6 to 7 hours.

5. The method for deodorizing plastic according to claim 1, wherein the power of the mid-infrared heating is 50 to 400kW.

6. The method of deodorizing a plastic according to claim 1, wherein said vacuum level is 100Pa or less.

7. The method for deodorizing plastic according to claim 1, wherein the plastic particles have an average particle size of 0.5 to 2mm.

8. The method of deodorizing plastic according to claim 1, wherein the plastic particles are continuously agitated during the mid-infrared heat treatment.

9. The method of deodorizing a plastic according to claim 1, wherein said plastic particles are recycled plastic.

10. The method of claim 1, wherein the ratio of the melt flow rate of the deodorized plastic to the plastic particles to be treated is not more than 1.1.