JPH0670094B2 - Method for producing low molecular weight polyolefin - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a low molecular weight polyolefin. More specifically, it relates to a method for producing industrially useful low molecular weight polyolefin.

[Prior Art] Conventionally, as a method of pyrolyzing a polyolefin to produce a low-molecular-weight polyolefin, a method of heating the polyolefin at 250 to 600 ° C. in an inert gas is known (for example, British Patent No. 569043, US Patent No. 2835659, Japanese Patent Publication No. 36-
8737 and Japanese Patent Publication No. 43-9368).

[Problems to be Solved by the Invention] However, the conventional techniques are not satisfactory in industrially producing stable products in various qualities such as hue (for example, odor).

[Means for Solving the Problems] The present inventors have arrived at the present invention as a result of intensive studies for industrially producing low-molecular polyolefins having various stable quality such as hue.

That is, the present invention is a method for continuously producing a low molecular weight polyolefin having a heat average molecular weight of 500 to 10,000 by thermally degrading a polyolefin in a tubular reactor in an inert gas (hereinafter referred to as the above method in this section), Thermal degradation at 300-450 ℃ for 0.5-10 hours and formula [In the formula, d: density of polyolefin at 23 ° C. (g / cm ³ ),
σ: Degradation amount of polyolefin per unit time (kg / h
r), D: inner diameter (m) of tubular reactor, L: length of tubular reactor (m), T: degradation temperature (° C). ] The manufacturing method of low molecular weight polyolefin characterized by performing on the conditions of satisfying;
A method for producing a low-molecular-weight polyolefin characterized in that, in the above-mentioned method, two or more tubes having different inner diameters are connected in series as a tubular reactor and carried out at 300 to 450 ° C. for 0.5 to 10 hours;
In the above method, the tubes having different inner diameters are represented by the formula (2)
The manufacturing method according to claim 2, comprising a front pipe and a final pipe satisfying (5) 0.2 ≦ D1 / De ≦ 0.8 (2) 150 ≦ L1 / D1 ≦ 1500 (3) 200 ≦ Le / De ≦ 800 (4) 0.3 ≦ (L1 × De) / (Le × D1) ≦ 4.0 (5) [In the formula, D1: front pipe inner diameter, De: final pipe inner diameter, L1: front pipe length, Le: final pipe length Show. ] In the above method, using a tubular reactor having a tube length of 5 to 200 m, 0.2 to 2
A method for producing a low-molecular-weight polyolefin characterized in that polyolefin is passed through the tubular reactor at a linear velocity of 5 to 100 m / hr at a pressure of 00 kg / cm ³ at 300 to 450 ° C. for 0.5 to 10 hours; In the method, a static mixer is used as a part or all of the tubular reactor at 300 to 450 ° C.
Method for producing low molecular weight polyolefin characterized by carrying out 0.5 to 10 hours; thermal degradation [In the formula, d: density of polyolefin at 23 ° C. (g / cm ³ ),
σ: Degradation amount of polyolefin per unit time (kg / h
r), D: inner diameter (m) of tubular reactor, L: length of tubular reactor (m), T: degradation temperature (° C). The method according to claim 5, wherein the tubular reactor is immersed in a bath of an inorganic salt mixture at 300 to 450 ° C for 0.5 to 10 hours. A low molecular weight polyolefin production method characterized by: a number average molecular weight of 500 to 10,000 obtained by thermal degradation of polyolefin in an inert gas.
In the method for producing a low-molecular-weight polyolefin, a phenol-based antioxidant 0.0
A method for producing a low molecular weight polyolefin, which is carried out at 300 to 450 ° C. for 0.5 to 10 hours in the presence of 1 to 0.2 parts by weight; and a low molecular weight polyolefin in which two or more of the methods according to any one of claims 1 to 8 are combined. It is a manufacturing method.

In the present invention, the polyolefin is a homopolymer of α-olefin selected from the group consisting of ethylene, propylene, 1-butene and 4-methyl-1-pentene, or a copolymer consisting of two or more of these α / olefins or Examples thereof include copolymers of one or more α-olefins with one or more other α-olefins and / or vinyl compounds. Other α-olefins include olefins having 5 to 18 carbon atoms, such as 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene. Examples of the vinyl compound include unsaturated carboxylic acid or its anhydride [(meth) acrylic acid, maleic anhydride, etc.] and alkyl (meth) acrylate (the alkyl group is a group selected from the group consisting of methyl, ethyl and butyl). Be mentioned).

Polyolefin melt flow rate is typically 0.5 to 2
It is 00 (g / 10min), preferably 1 to 100 (g / 10min). The number average molecular weight is usually 12,000 to 100,000, preferably 15,000 to 70,000.

The density of polyolefin at 23 ℃ is usually 0.85-1 (g /
cm ³ ).

An example of the manufacturing method of the present invention will be described with reference to the drawings. In FIG. 1, 1 is a front tube of a tubular reactor, 2 is a final tube, 3 is a gas-liquid separator, 4 is an inert gas blowing port, 5 is a heat medium (salt bath) container, 6 is a salt bath, and 7 Is a salt bath agitator.

After the polyolefin enters the tubular reactor and is heated and degraded, the volatile gaseous substances are removed by the gas-liquid separator to become a low molecular weight polyolefin.

The inner diameter (D) of the tubular reactor is usually 10 to 300 mm, preferably 20 to 200 mm. Length (L) is usually 5 to 2
The length is 00 m, preferably 10 to 150 m.

When the length of the tubular reactor is less than 5 m, the odor of the obtained low molecular weight polyolefin increases and it is difficult to obtain a homogeneous product. 200 m
If it exceeds, the hue will deteriorate.

Tubular reactor length to inner diameter ratio (L / D) is usually 50 to 200
It is 0, preferably 120 to 1500.

Tubular reactors usually have two or more stages of tubular reactors with different inner diameters.
Preferably two to five stages, particularly preferably two stages connected in series are used. Even though the tubular reactor is straight,
It may also have a spiral shape.

The ratio of the inner diameter of the front pipe (D1) to the inner diameter of the final pipe (De) (D1 / D
e) is usually 0.2 to 0.8, preferably 0.3 to 0.7. When D1 / De is less than 0.2, the hue of the obtained low molecular weight polyolefin becomes poor, and when it exceeds 0.8, the odor increases.

The ratio of the length of the front tube (L1) to D1 (L1 / D1) is usually 150 to 1500, preferably 200 to 1200. L1 / D1 is 150
When it is less than 1, the odor of the obtained low molecular weight polyolefin becomes large, and when it exceeds 1500, the hue is deteriorated.

The ratio of the final tube length (Le) to De (Le / De) is usually 200 to 800, preferably 250 to 700. When Le / De is less than 200, the odor of the obtained low molecular weight polyolefin becomes large,
If it exceeds 800, the hue becomes poor.

The ratio of L1 / D1 and Le / De [(L1 × De) / (Le × D1)] is usually
It is 0.3 to 4.0, preferably 0.5 to 3.5. (L1 x De)
When / (Le × D1) is less than 0.3, the hue of the obtained low molecular weight polyolefin becomes poor, and when it exceeds 4.0, the odor increases.

When the tubular reactor is composed of three or more stages, the inner diameter of the intermediate pipe (the pipe from the second stage to the stage before the final stage) is not particularly limited, but it is preferable to gradually increase. The length may be set arbitrarily.

In the present invention, a static mixer can be used as a part or a front part of the tubular reactor. Ordinary static mixer, eg "static mixer"
(Nikkan Kogyo Shimbun, published September 30, 1981), pages 5 and 6, and so on. Using a static mixer has the advantage of reducing odor.

The ratio of the length (L) of the static mixer to the inner diameter (D: expressed by the inner diameter of the passage tube) is usually 50 to 2000, preferably
120 to 1500.

The static mixer can be used for some or all of the tubular reactors. When used for a part, a normal tube can be used for the remainder. In addition, the position of the static mixer is not particularly limited when used partially. That is, any of the first half, the second half and the middle of the tubular reactor may be used, but the first half is preferable. The position to be used may be one place or two or more places.

In the production method of the present invention, it is preferable to use a salt bath as the heating medium bath. Lithium chloride-
Examples thereof include mixed salts of potassium chloride, lithium sulfate-potassium sulfate, sodium nitrate-potassium nitrate, sodium nitrite-potassium nitrate, sodium hydroxide-potassium hydroxide and the like. Among these, preferred is a mixed salt of sodium nitrite-potassium nitrate.

The weight ratio when mixing salt is not particularly limited,
Preferably, the melting point of the mixed salt is selected to be 50 to 200 ° C.

The heating method is usually performed with an electric heater. The temperature adjustment is not particularly limited, but it is preferably within a control range of ± 0.2 ° C or less. Outside this range, it is difficult to obtain a homogeneous polyolefin.

The reaction in the present invention is usually carried out in an inert gas. Examples of the inert gas include argon, nitrogen, carbon dioxide gas and water vapor. Preferred is nitrogen. Flow rate is usually 5
Or 100 l / min.

A catalyst may be used for the purpose of promoting the reaction. The catalyst is a radical generating catalyst [benzoyl peroxide,
Peroxides such as di-tert-butyl peroxide and dicumyl peroxide; 2,2'-azobis (isobutyronitrile), 2,2'-azobis (2,4-dimethylvaleronitrile) and 4,4 Azonitriles such as'-azobis (4-cyanovaleric acid)] and cracking catalysts (silica-alumina, silica-magnesia, activated clay, etc.) and the like.

The amount of catalyst used is usually 0.1 per 100 parts by weight of polyolefin.
To 20 parts by weight, preferably 1 to 10 parts by weight.
Addition of catalyst to the polyolefin is usually done before entering the tubular reactor.

The reaction temperature is 300 to 450 ° C, preferably 320 to 430 ° C.
If the reaction temperature is less than 300 ° C, the reaction will take a long time (usually 30
(More than time), the hue of the obtained low molecular weight polyolefin becomes poor. Odor increases above 450 ° C.

The reaction time is 0.5 to 10 hours, preferably 1 to 7 hours. When the reaction time is less than 0.5 hours, the odor of the obtained low molecular weight polyolefin increases and it is difficult to obtain a homogeneous product. Hue becomes worse after 10 hours.

Deterioration amount of polyolefin is usually 10 to
It is 700 kg, preferably 50 to 500 kg.

The pressure is usually 0.1 to 200 kg / cm ² , preferably 0.5 to 1
It is 50 kg / cm ² . Pressure is poor hue of low molecular polyolefin that is example less than 0.2 kg / cm ^2, odor increases exceeds 200 kg / cm ^2.

In the present invention, the formula [In the formula, d: Density of polyolefin at 23 ° C (g / cm ³ )
σ: Degradation amount of polyolefin per unit time (kg / h
r), D: inner diameter (m) of tubular reactor, L: length of tubular reactor (m), T: degradation temperature (° C). ] Thermal degradation is performed so that Preferably Under the condition that 0.5 to 70.

When the ratio is less than 0.3, the hue of the obtained low molecular weight polyolefin becomes poor, and when it exceeds 100, the odor increases.

When using a static mixer as a tubular reactor in part or in whole, thermal degradation is [In the formula, d, σ, D, T and L are the same as in the case of the formula (1). ] Is satisfied. Preferably Under the condition that is 0.5 to 300.

When the ratio is less than 0.3, the hue of the obtained low molecular weight polyolefin becomes poor, and when it exceeds 500, the odor increases.

When the tubular reactor has two or more stages, the inner diameter (D) and the length (L) of the tube are calculated by the following equations.

[In the formula, L1, L2 ...: First-stage pipe, second-stage pipe length, ... Stage pipe length, Le: Final-stage pipe length, D1, D2 ...: First-stage pipe and second-stage pipe, respectively ...... Inner diameter of the tube in the first stage, De: Indicates the inner diameter of the tube in the last stage. ] When the tubular reactor is a static mixer, the inner diameter (D) of the tube indicates the inner diameter of the passage tube of the static mixer,
The length is indicated by the length of the static mixer.

In the present invention, the linear flow velocity of polyolefin is usually 0.5.
To 100 m / hr, preferably 1 to 80 m / hr. When the linear velocity is less than 0.5 m / hr, the hue of the obtained low molecular weight polyolefin becomes poor, and when it exceeds 100 m / hr, the odor increases.

In the present invention, a phenolic antioxidant is usually added to perform thermal degradation.

A hindered phenolic compound is preferable as the phenolic antioxidant. Hindered phenol compounds include monocyclic hindered phenols such as 2,6-di-te
rt-Butyl-4-methylphenol (BHT), 2-tert-butyl-4-methylphenol (BHA), 6-tert-butyl-
2,4-Methylphenol (24M6B), 2,6-di-tert-butylphenol (26B), 2-tert-butyl-4-methylphenol (26M6B), 2,6-di-tert-butyl-4-ethyl Phenol, n-octadecyl-3- (4'-hydroxy-3,5-di-
(tert-butylphenyl) propionate, dioctadecyl-4-hydroxy-3,5-di-tert-butylbenzylphosphonate, diethyl-4-hydroxy-3,5-di-tert
-Butylbenzylphosphonate and 6- (4-oxy-3,5-di-tert-butyl-anilino) 2,4-bis (n-octylthio) -1,3,5-triazine; bicyclic hindered Phenols, such as 4,4'-thiobis (6-tert-butyl-3-
Methylphenol), 4,4'-butylidene bis (6-tert-
Butyl-3-methylphenol), 4,4'-methylenebis (6-tert-butylphenol), 4,4'-bis (2,6-di-
tert-butylphenol), 4,4'-thiobis (6-tert-
Butyl-o-cresol), 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,2'-thiobis (6-tert-butyl-4-methylphenol) and 1,6-bis ( 3,5-di-tert-butyl-4-hydroxy-2-methylphenyl) butane; and polycyclic (tricyclic or higher) hindered phenols such as 1,1,3-tris (5-tert-butyl- Four
-Hydroxy-2-methylphenyl) butane, 2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) mesitylene, 1,3,5-tris (3,5-di-tret -Butyl-4-hydroxybenzyl) mesitylene, 1,3,5-tris (3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate and tetrakis [β- (3,5-di-tert-butyl -Four
-Hydroxyphenyl) propionyloxymethyl] methane and the like.

Of these, preferably 2,6-di-tert-butyl-4-methylphenol, 2-tert-butyl-4-methylphenol, n
-Octadecyl-3- (4'-hydroxy-3,5-di-tert-
Butylphenyl) propionate and tetrakis [β- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxymethyl] methane, particularly preferred is tetrakis [β- (3,5-di-trt- Butyl-4-
Hydroxyphenyl) propionyloxymethyl] methane.

The amount of the phenolic antioxidant added is usually 0.01 to 0.2 part by weight, preferably 0.02 to 0.15 part by weight, based on 100 parts by weight of the polyolefin. If it is less than 0.01 part by weight, the hue of the obtained low molecular weight polyolefin will be poor, and if it exceeds 0.2 part by weight, the odor will increase.

The method for adding the phenolic antioxidant is not particularly limited. For example, it may be added before thermal degradation or may be added during thermal degradation.

The low-molecular polyolefin obtained in this way is usually
It is molded into powder or pellets through a purification process for removing extremely low molecular weight substances. The purification and molding methods are not particularly limited and may be ordinary methods.

The low molecular weight polyolefin obtained by the present invention is usually 50
It has a number average molecular weight of 0 to 10,000.

Hues usually has Hazen of 500 or less, softening point of 90 to 210
℃ or melt viscosity at 140 ℃ or 160 ℃ 20 to 100,
It is 000 cps.

[Examples] Hereinafter, the present invention will be further described with reference to Examples, but the present invention is not limited thereto. Parts in the examples are parts by weight.

Example 1 The density at 23 ° C. is 0.920 and the melt flow rate is 2.0.
(G / 10min) high-pressure polyethylene was dipped in a salt bath (mixed salt of sodium sulfite-potassium nitrate at a weight ratio of 45:55) controlled at 410 ± 0.1 ° C and the inner diameter was 49.5 mm.
While introducing nitrogen at a rate of 15 l / min into a tubular reactor consisting of a front tube with a length of 60 m and a rear tube with an inner diameter of 97.1 mm and a length of 50 m, 180
Thermal degradation was continuously performed at a flow rate of kg / hr. The obtained low molecular weight polyethylene has a number average molecular weight of 2200 and a hue (Hazen).
It was a colorless wax with almost no odor and a melt viscosity of 350 cps at a softening point of 109 ° C and 140 ° C.

Example 2 Density at 23 ° C. is 0.957 and Melt Flow Rate is 12.2
The same procedure as in Example 1 was carried out except that low pressure polyethylene of (g / 10 min) was used. The obtained low molecular weight polyethylene was a colorless wax with almost no odor, having a number average molecular weight of 4,200, a hue (Hazen) of 50, a softening point of 127 ° C. and a melt viscosity of 3300 cps at 140 ° C.

Example 3 Used in Example 1 while introducing 10 l / min of nitrogen into a tubular reactor having an inner diameter of 73.9 mm and a length of 100 m immersed in the same salt bath as in Example 1 whose temperature was controlled to 395 ± 0.1 ° C. High-pressure polyethylene at a pressure of 50 kg / cm ³ and a linear velocity of 45 m / hr for 2 hours
Thermal degradation was continuously performed for 10 minutes. The obtained low molecular weight polyethylene has a number average molecular weight of 3300, a hue (Hazen) of 30, and a softening point.
It was a colorless and almost odorless wax with a melt viscosity of 880 cps at 111 ° C and 140 ° C.

Example 4 23 ° C. instead of the high-pressure polyethylene used in Example 3.
At a density of 0.900 and a melt flow rate of 6.0 (g / 10
The same procedure as in Example 3 was carried out except that (min) polypropylene was used. The low molecular weight polyethylene obtained has a number average molecular weight.
3000, hue (Hazen) 100, softening point 147 ℃ and 160 ℃
It was a slightly yellow wax with a melt viscosity of 100 cps and almost no odor.

Example 5 Example 5 was repeated except that the front tube of the tubular reactor used in Example 1 was a fixed-blade static mixer. The obtained low molecular weight polyethylene has a number average molecular weight of 2400,
It was a colorless and odorless wax having a hue (Hazen) of 50, a softening point of 109 ° C. and a melt viscosity of 390 cps at 140 ° C.

Example 6 2-te as an antioxidant before passing through the tubular reactor in Example 2
Example 2 was repeated except that 0.05% of rt-butyl-4-methoxyphenol was added to polyethylene. The obtained low molecular weight polyethylene has a number average molecular weight of 4400, a hue (Hazen) 20, a softening point of 128 ° C and a melt viscosity of 3400 at 140 ° C.
It was a colorless cps wax with almost no odor.

[Effects of the Invention] By the production method of the present invention, it is possible to industrially produce stable low-molecular polyolefins having various qualities such as hue. Specifically: 1. A low molecular weight polyolefin with a good hue can be obtained.

2. A low molecular weight polyolefin with little odor can be obtained.

3. A low molecular weight polyolefin with good thermal stability can be obtained.

4. Efficient industrial scale production of low molecular weight polyolefin by thermal degradation.

The low-molecular polyolefin obtained in the present invention having the above-mentioned effects can be suitably used as a pigment dispersant for plastics, a processability improver for plastics, a rubber additive, an ink, a compounding agent for paints and a release agent for toners. .

[Brief description of drawings]

 FIG. 1 is a flow chart showing an embodiment of the present invention. 1 and 2: Tubular reactor 6: Salt bath

Claims (9)

[Claims] 1. A method for continuously producing a low-molecular polyolefin having a number average molecular weight of 500 to 10,000 by thermally degrading a polyolefin in an inert gas in a tubular reactor, wherein the thermal degrading is performed.
0.5 ~ 10 hours at 300 ~ 450 ℃ and formula [In the formula, d: density of polyolefin at 23 ° C. (g / cm ³ ),
σ: Degradation amount of polyolefin per unit time (kg / h
r), D: inner diameter (m) of tubular reactor, L: length of tubular reactor (m), T: degradation temperature (° C). ] The manufacturing method of the low molecular polyolefin characterized by performing on the conditions satisfy | filled. 2. A method for continuously producing a low-molecular-weight polyolefin having a number average molecular weight of 500 to 10,000 by thermally decomposing a polyolefin in an inert gas in a tubular reactor, wherein two tubes having different inner diameters are used as the tubular reactor. 300 or more connected in series
A method for producing a low-molecular-weight polyolefin, which comprises performing thermal degradation for 0.5 to 10 hours at ~ 450 ° C. 3. A tube according to claim 2, wherein the tubes having different inner diameters are a first-stage reactor (hereinafter referred to as a front tube) and a final-stage reactor (hereinafter referred to as a final tube) satisfying the formulas (2) to (5). Manufacturing method. 0.2 ≦ D1 / De ≦ 0.8 (2) 150 ≦ L1 / D1 ≦ 1500 (3) 200 ≦ Le / De ≦ 800 (4) 0.3 ≦ (L1 × De) / (Le × D1) ≦ 4.0 (5) [Formula] Medium, D1: front pipe inner diameter, De: final pipe inner diameter, L1: front pipe length, Le: final pipe length. ] 4. A method for continuously producing a low-molecular polyolefin having a number average molecular weight of 500 to 10,000 by thermally decomposing a polyolefin in a tubular reactor in an inert gas, and using a tubular reactor having a tube length of 5 to 200 m. A low molecular weight compound, characterized in that thermal degradation is carried out by passing a polyolefin through the tubular reactor at 300 to 450 ° C. for 0.5 to 10 hours at a linear velocity of 5 to 100 m / hr under a pressure of 0.2 to 200 kg / cm ^3. Manufacturing method of polyolefin. 5. A method for continuously producing a low molecular weight polyolefin having a number average molecular weight of 500 to 10,000 by thermally degrading a polyolefin in an inert gas at 300 to 450 ° C. for 0.5 to 10 hours in a tubular reactor, wherein A process for producing a low-molecular-weight polyolefin, characterized in that a static mixer is used as a part or all of the reactor to perform thermal degradation at 300 to 450 ° C for 0.5 to 10 hours. 6. A thermal degradation formula [In the formula, d: density of polyolefin at 23 ° C. (g / cm ³ ),
σ: Degradation amount of polyolefin per unit time (kg / h
r), D: inner diameter (m) of tubular reactor, L: length of tubular reactor (m), T: degradation temperature (° C). ] The manufacturing method of Claim 5 performed on the conditions satisfy | filled. 7. The production method according to claim 1, 2 or 4, wherein the tubular reactor is immersed in a bath containing an inorganic salt mixture for thermal degradation. 8. The method according to claim 1, wherein the thermal degradation is carried out in the presence of 0.01 to 0.2 parts by weight of a phenolic antioxidant with respect to 100 parts by weight of the polyolefin. 9. A method for producing a low molecular weight polyolefin, which is a combination of two or more of the methods according to any one of claims 1 to 8.