Method for producing pyrolysis wax

Abstract

To shorten the time required for the production process of a pyrolysis wax, by promoting pyrolysis without the mixing of inorganic compounds and the formation of oxides, in the production of a pyrolysis wax due to the pyrolysis of polyethylene.SOLUTION: A method for producing a pyrolysis wax includes adding a polyolefin decomposition promoter (B) to polyethylene (A), to thermally decompose the polyethylene (A).SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to an efficient method for producing pyrolysis wax. [Background technology]

[0002] Low molecular weight polymers with a molecular weight of 10,000 or less exhibit different physical and chemical properties from common polymers with molecular weights of tens of thousands to hundreds of thousands. Among them, polyolefin waxes such as low molecular weight polyethylene and low molecular weight polypropylene show high compatibility not only with polyolefins, which make up a large portion of the plastics produced, but also with resins such as polyvinyl chloride, and are used in a wide range of applications such as pigment dispersants, molding aids, additives for inks or paints, and additives for hot melt adhesives.

[0003] Polyolefin waxes are generally classified as synthetic waxes into polymerization type and thermal decomposition type. The thermal decomposition method has commercial advantages such as lower manufacturing costs and suitability for small-scale production compared to the polymerization method, as well as being a useful method from the perspective of environmental considerations, which have become increasingly important in recent years, as it can utilize discarded plastics. However, polyolefins have a higher thermal decomposition temperature compared to other polymers, and obtaining wax requires thermal decomposition at high temperatures for a long period of time, thus requiring a lot of energy in the thermal decomposition process. For this reason, several methods have been proposed to accelerate the thermal decomposition reaction, including methods of adding oxygen and peroxides (e.g., Patent Document 1), methods of adding mercaptan-based organic compounds (e.g., Patent Document 2), and methods of reacting with a catalytic catalyst (e.g., Patent Document 3). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Special Publication No. 51-48196 [Patent Document 2] Japanese Patent Application Publication No. 9-40801 [Patent Document 3] Special Publication No. 2019-515060 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Thus, while accelerating the decomposition of polyolefins by adding compounds that act as decomposition accelerators is useful from an energy-saving standpoint, several problems arise. Patent Document 1 exemplifies a method that accelerates the decomposition of propylene polymers using oxygen and peroxides, but this may cause changes in the physical properties of the propylene polymer due to oxidation and secondary decomposition by peroxides remaining in the product.

[0006] In the method proposed in Patent Document 2, a method is exemplified in which a mercaptan-based organic compound is used as a decomposition accelerator in the thermal decomposition of synthetic polymers, but the harmful effects on the human body and the odor of mercaptan-based organic compounds are problematic.

[0007] Furthermore, while Patent Document 3 provides an example of a method that uses a contact catalyst to convert plastic into wax, the catalyst is generally expensive, the process needs to be stopped to regenerate and replace the deactivated catalyst, and there are issues such as the catalyst being mixed into the wax.

[0008] Therefore, in the production method of pyrolysis wax using polyethylene as a raw material, there is a need for a method that promotes pyrolysis without causing process problems or deterioration of the quality of the product. [Means for solving the problem]

[0009] As a result of diligent research to solve the aforementioned problems, the inventors discovered that the thermal decomposition time of polyethylene can be significantly shortened by adding a decomposition accelerator, and thus completed the present invention.

[0010] In other words, the various embodiments of the present invention are as follows [1] to

[11] . [1] A method for producing pyrolysis wax, comprising adding a polyolefin-based decomposition accelerator (B) to polyethylene (A) and thermally decomposing the polyethylene (A). [2] The method for producing pyrolysis wax according to [1] above, wherein the polyolefin-based decomposition accelerator (B) is a polyolefin-based compound having a lower density than polyethylene (A). [3] Polyolefin-based decomposition accelerator (B) 13 A method for producing a pyrolysis wax according to [1] or [2] above, wherein the polyethylene has 5 or more branched carbon atoms per 1000 main chain methylene carbon atoms as measured by 13C-NMR. [4] A method for producing pyrolysis wax according to any one of [1] to [3] above, wherein 1 part by weight or more and 100 parts by weight or less of a polyolefin-based decomposition accelerator (B) is added to 100 parts by weight of polyethylene (A). [5] The density of polyethylene (A) is 920 kg / m³. 3 More than 980kg / m 3 A method for producing a pyrolysis wax as described in any of the above [1] to [4]. [6] The density of the polyolefin-based decomposition accelerator (B) is 880 kg / m³. 3 More than 950kg / m 3 A method for producing a pyrolysis wax as described in any of the above [1] to [5], which is as follows: [7] A method for producing a pyrolysis wax according to any one of [1] to [6] above, wherein the pyrolysis temperature is 350°C or more and 500°C or less. [8] A method for producing a pyrolysis wax according to any one of [1] to [7] above, wherein the number average molecular weight (Mn) of the pyrolysis wax measured by GPC is 500 or more and 10,000 or less. [9] A method for producing a pyrolysis wax according to any one of [1] to [8] above, wherein the molecular weight distribution (Mw / Mn (where Mw is the weight-average molecular weight)) of the pyrolysis wax is 1.1 or more and 3.0 or less.

[10] A method for producing a pyrolysis wax according to any one of [1] to [9] above, wherein polyethylene (A) is used polyethylene.

[11] The method for producing the pyrolysis wax according to any one of [1] to

[10] above, characterized in that the polyolefin-based decomposition accelerator (B) is used polyethylene.

Effect of the Invention

[0011] According to the present invention, the time required for producing the pyrolysis wax by the pyrolysis of polyethylene can be shortened.

Embodiment for Carrying Out the Invention

[0012] Hereinafter, the method for producing the pyrolysis wax, which is one aspect of the present invention, will be described in detail.

[0013] The pyrolysis wax can be produced by adding a polyolefin-based decomposition accelerator (B) to polyethylene (A) and pyrolyzing the polyethylene (A). The polyethylene (A) used as a raw material is preferably a single component of polyethylene (A) or a composition containing polyethylene (A) and further other components. When the polyethylene (A) is a composition, it can be used in any state where each component is in a state of being dissolved in each other or in a state where each component is physically mixed in a solid state such as pellets or end materials. When the polyethylene (A) is a composition, it is preferably contained 80% by weight or more of the polyethylene resin, more preferably 95% by weight or more of the polyethylene resin, particularly preferably 99% by weight or more. If the polyethylene resin is contained 80% by weight or more, the produced low molecular weight polyethylene will not be yellowed or colored, and it is easy to remove components other than polyethylene, and the quality of the product will not deteriorate. Examples of the polyethylene resin constituting the polyethylene (A) include high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ultra-high molecular weight polyethylene, etc., and any one or two or more of these may be used.

[0014] The density of the polyethylene (A) is 920 kg / m 3 or more and 980 kg / m 3 or less is preferable. Since a pyrolysis wax having high heat resistance and mechanical strength can be obtained, 930 kg / m3 980 kg / m or more 3 and preferably 940 kg / m or less, 3 980 kg / m or more 3 and particularly preferably 940 kg / m or less.

[0015] The polyolefin-based decomposition accelerator (B) in the present invention thermally decomposes faster than the polyethylene (A) and promotes the decomposition of the polyethylene (A) by the radicals generated during the thermal decomposition. The polyolefin-based decomposition accelerator (B) is preferably a polyolefin-based compound having a lower density than the polyethylene (A), and examples thereof include polyethylene, polypropylene, etc., and polyethylene is particularly preferable because of its high compatibility with the polyethylene (A). When the polyolefin-based decomposition accelerator (B) is polyethylene, 13 it preferably contains 5 or more branched carbons per 1000 main-chain methylene carbons measured by C-NMR, more preferably 7 or more. Further preferably, it is 10 or more. The promotion effect of thermal decomposition is improved by the large number of branched carbons. The number of branched carbons is the sum of C2 short-chain branched tertiary carbons and C4 or more long-chain branched tertiary carbons, and the number of main-chain methylene carbons and the number of branched carbons are 13 determined by C-NMR measurement. The density of the polyolefin-based decomposition accelerator (B) is 880 kg / m 3 or more and 950 kg / m 3 or less is preferable. Since the shortening time of thermal decomposition by the polyolefin-based decomposition accelerator (B) is large, 880 kg / m 3 or more and 940 kg / m 3 or less is preferable, and 880 kg / m 3 or more and 930 kg / m 3 or less is particularly preferable.

[0016] In the present invention, it is preferable to add 1 to 100 parts by weight of a polyolefin-based decomposition accelerator (B) to 100 parts by weight of polyethylene (A) and perform thermal decomposition, more preferably 2 to 90 parts by weight, and particularly preferably 3 to 80 parts by weight. When the amount of polyolefin-based decomposition accelerator (B) is 100 parts by weight or less, the resulting thermally decomposed wax has excellent heat resistance and impact resistance. On the other hand, when the amount of polyolefin-based decomposition accelerator (B) is 1 part by weight or more, the effect of shortening the thermal decomposition time is significant.

[0017] Polyethylene (A) and polyolefin-based decomposition accelerator (B) may be not limited to pellets, powders, etc., but may also be molded products such as films, sheets, bottles, and their crushed products, or waste polyethylene referred to as used products, off-spec products, or discarded products.

[0018] The polyethylene (A), which is the raw material for the pyrolysis wax, is preferably pre-mixed with a polyolefin-based decomposition accelerator (B) before pyrolysis. The mixing method is not particularly limited and can be any method that can achieve uniform mixing, such as dry blending using a tumbler, or melt blending using a kneading device such as a single-screw extruder, multi-screw extruder, Banbury mixer, pressure kneader, rotary roll, or internal mixer. When kneading by melt blending, the kneading temperature is preferably around 160°C to 300°C.

[0019] Polyethylene (A) can be used as is, with antioxidants added during the manufacturing of the raw polyethylene resin or during molding into products such as films. Furthermore, antioxidants can be added during the thermal decomposition reaction to prevent oxidative degradation. There are no particular restrictions on the antioxidants to be added; for example, phenolic antioxidants such as 2,6-di-t-butyl-4-methylphenol, n-octadecyl-3-(4-hydroxy-3,5-di-t-butylphenyl)propionate, and tetrakis[β-(3,5-di-t-butyl-4-hydroxyphenyl)propionitrileoxymethyl]methane can be used. The amount or content added is 0.005 parts by weight or more and 0.5 parts by weight or less per 100 parts by weight of raw polyethylene, preferably 0.01 parts by weight or more and 0.1 parts by weight or less. Adding 0.005 parts by weight or more of antioxidant may improve the color or odor of the thermal decomposition wax. If the antioxidant is 0.5 parts by weight or less, no coke will be generated during thermal decomposition, nor will any unpleasant odor be produced.

[0020] The thermal decomposition reaction in this invention is carried out in an inert gas or under an inert gas atmosphere. Examples of inert gases include hydrogen, helium, argon, nitrogen, and carbon dioxide, either individually or in any proportion. Preferably, nitrogen is used because it is easily handled industrially, readily available, and relatively inexpensive. The inert gas may contain trace amounts of oxygen, but preferably it is 0.1% or less, and more preferably 100 ppm or less, in order to prevent oxidative degradation, discoloration, and odor generation of the thermal decomposition wax.

[0021] The thermal decomposition temperature in the thermal decomposition process is preferably in the range of 350°C to 500°C, as this allows for short-time thermal decomposition and suppresses oxidation and odor of the resulting thermally decomposed wax. Preferably, it is in the range of 365°C to 475°C, and particularly preferably 380°C to 450°C. If the thermal decomposition temperature is 500°C or lower, there is less odor, and if it is 350°C or higher, the reaction becomes uniform, resulting in a homogeneous thermally decomposed wax. Furthermore, it is economically advantageous as it does not require a long thermal decomposition time until the reaction is complete. The heating time in the thermal decomposition process is not particularly limited, but is usually in the range of 1 minute to 10 hours, and an appropriate time is selected to obtain the desired number-average molecular weight of the thermally decomposed wax. Preferably, it is in the range of 1 minute to 6 hours, as this suppresses oxidative degradation and odor, and particularly preferably, it is in the range of 2 minutes to 5 hours, as this improves ease of control and production efficiency.

[0022] The thermal decomposition reaction in this invention is carried out at a gauge pressure of -0.1 to 10 MPa, and a range of -0.05 to 1 MPa is preferred because it offers good operability and produces a good color for the resulting thermally decomposed wax.

[0023] There are no particular restrictions on the apparatus used to carry out the pyrolysis reaction, but any commonly used equipment is acceptable. Examples include hot plate heaters, electric furnaces, tubular electric furnaces, quartz mantle heaters, gas furnaces, gas-heated kilns, electric kilns and other kiln-type reactors, single-screw or twin-screw screw extruders, stainless steel autoclaves with agitators, quartz flasks, fluidized bed reactors, solid bed reactors, tubular reactors, and microwave heaters. Among these, hot plate heaters, electric furnaces, screw extruders, and kiln-type reactors are particularly recommended because they facilitate the removal of volatile components.

[0024] The pyrolysis wax produced by the manufacturing method of the present invention can be used in any form, such as pellets, powder, or flakes, after being purified. The methods of purification and molding are not particularly limited and can be conventional methods.

[0025] The weight-average molecular weight (Mw), number-average molecular weight (Mn), and molecular weight dispersion (weight-average molecular weight / number-average molecular weight) of polyethylene resins and pyrolysis waxes can be measured by general gel permeation chromatography (GPC). Note that Mw and Mn were determined as linear polyethylene equivalents.

[0026] The pyrolysis wax produced by the present invention's method for producing pyrolysis wax preferably has a number-average molecular weight of 500 to 10,000 as measured by gel permission chromatography (GPC), more preferably 1,000 to less than 8,000, and even more preferably 1,500 to 5,000. Furthermore, the molecular weight distribution (weight-average molecular weight Mw / number-average molecular weight Mn) is preferably 1.1 to 3.0, more preferably 1.3 to 2.5, and most preferably 1.5 to 2.3.

[0027] When the polyolefin-based degradation accelerator (B) is polyethylene, the main chain methylene carbon and branched carbons are determined using a Bruker AVANCE NEO700 nuclear magnetic resonance spectrometer. 13 The number of C2 branched tertiary carbons and long-chain branched tertiary carbons (C4 and above) was measured by 13C-NMR. The solvent used was orthodichlorobenzene-d4. The number of C2 branched tertiary carbons (39.4 ppm) and C4 and above branched tertiary carbons (38.0 ppm) was calculated as the number of carbons per 1,000 main-chain methylene carbons (30.0 ppm).

[0028] The pyrolysis wax produced by the manufacturing method of the present invention can be widely used as a plastic molding aid, such as a dispersant, release agent, lubricant, or plasticizer for fillers and pigments, as well as for modifying hot melt adhesives and other everyday products such as cosmetics, inks, and chemical papers. [Examples]

[0029] The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these. (1) Meltmass flow rate (MFR) Measurements were taken in accordance with JIS K6922-1 (1997). (2) Density Measurements were taken in accordance with JIS K6922-1 (1997). (3) GPC measurement Equipment: HLC-8321GPC / HT (Detector: RI type) (Manufactured by Tosoh Corporation) Columns: Use one column (i) and three columns (ii) in series. (i)TSKgel guArdColumuH(HR)(30)HT (7.5mm I.D.) x 7.5cm) (Manufactured by Tosoh Corporation) x 1 piece (ii) TSKgel GMH(HR)-H(20)HT (7.5mm I.D.) x 30cm) (Manufactured by Tosoh Corporation) x 3 pieces Eluent: 1,2,4-Trichlorobenzene (containing 0.05 wt% BHT) (Manufactured by Fujifilm Wako Pure Chemical Corporation) Flow rate: 1.0mL / min Injection volume: 0.3mL Column temperature: 140℃ Temperature: 40°C Sample concentration: 1 mg / mL Calibration curve: A fifth-order approximation curve using standard polystyrene manufactured by Tosoh Corporation. However, the molecular weight was converted to PE-equivalent molecular weight using the Q factor. (4) Pyrolysis time reduction rate The effect of adding the polyolefin-based decomposition accelerator (B) on shortening the thermal decomposition time is calculated as follows.

[0030] Let t(T-α-A) be the time it takes for the sample weight to decrease by α% when only polyethylene (A) is thermally decomposed at a thermal decomposition temperature T°C, and let t(T-α-B) be the time it takes for the sample weight to decrease by α% when a resin composition consisting of polyethylene (A) and a polyolefin-based decomposition accelerator (B) is thermally decomposed. In this case, the reduction time of thermal decomposition is expressed as (t(T-α-A)-t(T-α-B)), and the reduction rate is expressed as (1-(t(T-α-B) / t(T-α-A))). (5) Melting point measurement Measurements were taken in accordance with JIS K7122 (2012). [Example 1] 1) Create a sample Polyethylene (A) is manufactured by Tosoh Corporation, product name Nipolon Hard 1200 A-1 (number average molecular weight 13,300 g / mol, MFR 21 g / 10 min, density 952 kg / m³). 3 ), as a polyolefin-based decomposition accelerator (B), manufactured by Tosoh Corporation, trade name Petrocene 202K B-1 (number average molecular weight 14,700 g / mol, MFR 24 g / 10 min, density 918 kg / m³) 3 The following materials (with 13.2 branched carbon atoms per 1000 main chain methylene carbon atoms) were powdered using a freeze-dried pulverizer (JFC-5000, manufactured by Nippon Analytical Industry Co., Ltd.) at a weight ratio of 100:5 and mixed. The mixture was then press-molded using a press molding machine (AWFA-50, manufactured by Shinto Metal Industry Co., Ltd.) under the conditions of heating at 180°C (primary pressurization for 3 minutes, secondary pressurization for 3 minutes) and cooling at 25°C (for 4 minutes) to obtain a press sheet with a thickness of 1 mm. 2) Thermal decomposition reaction The prepared press sheet (10 cm long x 10 cm wide x 1 mm thick) was placed in an electric furnace on an aluminum sample stand mounted on a hot plate that was covered with a stainless steel shield capable of nitrogen exchange and whose weight could be measured over time. The internal temperature was adjusted to 30°C, and nitrogen gas was supplied into the reaction vessel at a constant flow rate of 50 mL / min for 30 minutes, while exhaust gas was vented through the vent line, thereby replacing the inside of the vessel with nitrogen gas. Next, nitrogen gas was supplied to the reactor at a constant flow rate of 50 mL / min, and the temperature was raised from room temperature at 10°C / min until it reached 420°C, at which point it was held at that temperature. When the sample weight decreased by 5% due to the generation of volatile pyrolysis products, heating and holding were stopped, and the sample was cooled by supplying nitrogen gas at 100 mL / min. After the internal temperature returned to room temperature, nitrogen gas was supplied for 30 minutes, and then the sample was collected. The pyrolysis time (time from the start of holding to the start of cooling) t(420-5-B) was 11 minutes. Various measurements were performed on the collected samples. The evaluation results are shown in Table 1. [Example 2] Sample preparation and thermal decomposition reaction were carried out in the same manner as in Example 1, except that the weight ratio of A-1 to B-1 was set to 100:54. The samples were then collected. The thermal decomposition time t(420-5-B) was 6 minutes. Various measurements were performed on the collected samples. The evaluation results are shown in Table 1. [Example 3] Sample preparation and pyrolysis were carried out in the same manner as in Example 2, except that cooling was started when the sample weight reduction rate due to the generation of volatile pyrolysis products in the pyrolysis reaction reached 20%. The sample was then collected. The pyrolysis time t(420-20-B) was 23 minutes. Various measurements were performed on the collected sample. The evaluation results are shown in Table 1. [Example 4] Sample preparation and pyrolysis were carried out in the same manner as in Example 1, except that the holding temperature during the pyrolysis reaction was set to 380°C. The sample was then collected. The pyrolysis time t(380-5-B) was 180 minutes. Various measurements were performed on the collected sample. The evaluation results are shown in Table 1. [Comparative Example 1] Sample preparation and thermal decomposition reaction were carried out in the same manner as in Example 1, except that the press sheet was made using only A-1, and the sample was recovered. The thermal decomposition time t(420-5-A) was 14 minutes. Various measurements were performed on the recovered sample. The evaluation results are shown in Table 1. [Comparative Example 2] Sample preparation and pyrolysis were carried out in the same manner as in Comparative Example 1, except that cooling was started when the sample weight loss rate due to the generation of volatile pyrolysis products in the pyrolysis reaction reached 20%. The sample was then recovered. The pyrolysis time t(420-20-A) was 37 minutes. Various measurements were performed on the recovered sample. The evaluation results are shown in Table 1. [Comparative Example 3] Sample preparation and pyrolysis were carried out in the same manner as in Comparative Example 1, except that the holding temperature during the pyrolysis reaction was set to 380°C. The sample was then collected. The pyrolysis time t(380-5-A) was 199 minutes. Various measurements were performed on the collected sample. The evaluation results are shown in Table 1.

[0031] [Table 1] [Industrial applicability]

[0032] The pyrolysis wax produced by the method of the present invention is suitably used as a plastic molding aid, such as a dispersant for fillers and pigments, a release agent, a lubricant, or a plasticizer.

Claims

1. A method for producing a pyrolysis wax by adding a polyolefin-based decomposition accelerator (B) to polyethylene (A) and thermally decomposing the polyethylene (A), wherein the polyolefin-based decomposition accelerator (B) is polyethylene with a lower density than polyethylene (A).

2. Polyolefin-based decomposition accelerator (B) １３ A method for producing pyrolysis wax according to claim 1, wherein the polyethylene has 5 or more branched carbon atoms per 1000 main chain methylene carbon atoms as measured by 13C-NMR.

3. A method for producing pyrolysis wax according to claim 1 or 2, wherein 1 to 100 parts by weight of a polyolefin-based decomposition accelerator (B) is added to 100 parts by weight of polyethylene (A).

4. The density of polyethylene (A) is 920 kg / m³. ３ More than 980kg / m ３ The method for producing a pyrolysis wax according to any one of claims 1 to 3, as follows:

5. The density of the polyolefin-based decomposition accelerator (B) is 880 kg / m³. ３ More than 950kg / m ３ The method for producing a pyrolysis wax according to any one of claims 1 to 4, as follows:

6. A method for producing a pyrolysis wax according to any one of claims 1 to 3, wherein the density of polyethylene (A) is 930 kg / m³ or more and 980 kg / m³ or less, and the density of the polyolefin-based decomposition accelerator (B) is 880 kg / m³ or more and 930 kg / m³ or less.

7. A method for producing a pyrolysis wax according to any one of claims 1 to 6, wherein the pyrolysis temperature is 350°C or higher and 500°C or lower.

8. A method for producing a pyrolysis wax according to any one of claims 1 to 7, wherein the number-average molecular weight (Mn) of the pyrolysis wax measured by GPC is 500 or more and 10,000 or less.

9. A method for producing a pyrolysis wax according to any one of claims 1 to 8, wherein the molecular weight distribution (Mw / Mn (where Mw is the weight-average molecular weight)) of the pyrolysis wax is 1.1 or more and 3.0 or less.

10. A method for producing a pyrolysis wax according to any one of claims 1 to 9, wherein polyethylene (A) is used polyethylene.

11. A method for producing pyrolysis wax according to any one of claims 1 to 10, characterized in that the polyolefin-based decomposition accelerator (B) is used polyethylene.

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