JP2016221772A - Method for granulating soft resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for granulating a soft resin that can perform stable granulation.SOLUTION: The method for granulating a soft resin includes: bringing the soft resin into a molten state; using a multi-tube heat exchanger to reduce temperature of the soft resin; discharging the soft resin from a die outlet; and cutting it underwater by a rotary cutter to perform underwater granulation.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for granulating a soft resin.

  Soft resins such as soft polyolefin resins are widely used as raw materials for films and the like as substitutes for soft vinyl chloride resins having a large environmental load. The soft polyolefin resin is granulated to a size that is easy to handle as a product after polymerizing the monomers.

  As a method for granulating the soft resin, for example, as described in Patent Document 1, crystalline polypropylene and amorphous polyolefin previously melted are supplied to a twin-screw extruder, and this extrusion is performed. There is a method in which a soft polyolefin resin having these compositions melt-kneaded by a machine is extruded from a die hole and cut with a rotary blade in a cutting chamber of an underwater cut pelletizing system.

  Further, in Patent Document 2, as an efficient granulation method that does not cause re-fusion between granulated products even after granulation, a soft polyolefin resin in a melted state by a devolatilization step after polymerization is used as a resin. And a step of cooling the cooled resin to a temperature range of ± 50 ° C. and a step of granulating the cooled resin by an underwater granulation method, wherein the temperature of the cooling water in the underwater granulation method is A granulation method of a soft polyolefin resin, which is 30 ° C. or lower and in which an anti-fusing agent is added to the cooling water, is described.

JP-A-7-88839 JP 2006-328350 A

However, these documents pay attention to the problem of re-fusion of pellets after granulation, and provide a solution to the problem. On the other hand, in the conventional underwater granulation method, the soft granulation is performed. Depending on the nature of the resin, when the molten soft resin is directly discharged into water, there is a problem that the discharged resin is wound around the rotary blade.
This invention solves such a subject and provides the granulation method of the soft resin in which stable granulation is possible.

  In the underwater granulation method, the present inventors can solve the above-mentioned problem by lowering the temperature of the soft resin using a multitubular heat exchanger and adjusting the viscosity of the molten soft resin before underwater granulation. I found out.

The present invention relates to the following [1] to [9].
[1] The soft resin is melted, and then the temperature of the soft resin is lowered using a multi-tube heat exchanger, and then the soft resin is discharged from the die outlet and cut with a rotary blade in water. A method for granulating a soft resin, characterized by granulating.
[2] The method for granulating a soft resin according to [1], wherein the temperature is lowered to a temperature at which the viscosity of the soft resin becomes 30 Pa · s or more by the multi-tube heat exchanger.
[3] The method for granulating a soft resin according to [1] or [2], wherein a temperature difference of the soft resin in the radial direction at the die outlet is 10 ° C. or less.
[4] The method for granulating a soft resin according to any one of [1] to [3], wherein the ratio of the outlet viscosity and the inlet viscosity of the soft resin in the multitubular heat exchanger is 5.0 or less.
[5] The method for granulating a soft resin according to any one of [1] to [4], wherein a difference between an outlet temperature and an inlet temperature of the refrigerant flowing through the multi-tube heat exchanger is 10 ° C. or less.
[6] The soft resin granulation method according to any one of [1] to [5], wherein the multi-tube heat exchanger includes a static mixer in a pipe through which the soft resin passes.
[7] The soft resin granulation method according to any one of [1] to [6], wherein a flow path length / body diameter ratio (L / D ratio) of the multitubular heat exchanger is 2 to 10.
[8] The soft resin granulation method according to any one of [1] to [7], wherein the soft resin is a propylene polymer satisfying at least one of (1) and (2).
(1) [mmmm] is 20 to 60 mol%.
(2) Using a differential scanning calorimeter (DSC), hold the sample at −10 ° C. for 5 minutes in a nitrogen atmosphere, and then raise the temperature at 10 ° C./min. The melting point (Tm-D) defined as the observed peak top is 0-120 ° C.
[9] The tensile elastic modulus of the soft resin is 1 to 200 MPa, and the melt flow rate (MFR) of the soft resin at a temperature of 230 ° C. and a load of 21.18 N is 1 to 10,000 g / 10 minutes. The method for granulating a soft resin according to any one of [1] to [8].

  According to the present invention, it is possible to provide a soft resin granulation method capable of stable granulation.

FIG. 1 is a diagram schematically showing a basic configuration of an apparatus according to a first embodiment used in the present invention. FIG. 2 is a cross-sectional view schematically showing the basic configuration of a multi-tube heat exchanger used in the present invention. FIG. 3 is a diagram schematically showing the basic configuration of the apparatus of the second embodiment used in the present invention.

In the granulation method of the soft resin of the present invention, the soft resin is made into a molten state, and then the soft resin is cooled using a multi-tubular heat exchanger, and then the soft resin is discharged from a die outlet, Cut with a rotary blade and granulate in water. Providing a soft resin granulation method in which the soft resin viscosity can be adjusted moderately and stable granulation can be achieved by lowering the temperature of the molten soft resin using a multi-tube heat exchanger. It becomes possible to do.
In the granulation method of the present invention, the temperature is preferably lowered to a temperature at which the soft resin has a viscosity of 30 Pa · s or higher (more preferably 40 Pa · s or higher, more preferably 50 Pa · s or higher) in a multi-tube heat exchanger. .

Although stable granulation is possible by lowering the temperature using a multitubular heat exchanger, the soft resin in a molten state cooled by the multitubular heat exchanger has temperature unevenness in the radial direction. It has been found that the discharged soft resin has a problem that it is easily wound around the rotary blade.
That is, in the granulation method of the present invention, from the viewpoint of performing remarkably stable granulation, preferably, the temperature difference of the soft resin in the radial direction at the die outlet (hereinafter, also simply referred to as “exit temperature difference”). Is 10 ° C. or less.
The outlet temperature difference is preferably 10 ° C. or less, more preferably 7 ° C. or less, and still more preferably 5 ° C. or less, from the viewpoint of performing remarkably stable granulation.
In addition, the temperature difference of the resin in the radial direction means the maximum temperature difference between the central portion and the outer peripheral portion in the vertical cross section with respect to the direction in which the resin flows near the die outlet. Here, the center portion refers to a die hole located at a location closest to the center of the vertical cross section, and the outer peripheral portion refers to a die hole located at a location farthest from the center of the vertical cross section.

In the granulation method of the present invention, the ratio between the outlet viscosity and the inlet viscosity of the soft resin in the multi-tubular heat exchanger is preferably 20 or less, more preferably 10 or less, from the viewpoint of performing remarkably stable granulation. More preferably, it is 5.0 or less, more preferably 4.8 or less, and still more preferably 4.6 or less. The ratio is not particularly limited, but is, for example, 2.0 or more. Here, the exit viscosity and the entrance viscosity can be calculated from the temperature of the soft resin, a calibration curve prepared in advance, and the like.
Note that the temperature of the soft resin after the temperature drop is preferably higher than the melting point of the soft resin.

In the granulation method of the present invention, the difference between the outlet temperature and the inlet temperature of the refrigerant circulating in the multi-tubular heat exchanger reduces the temperature unevenness of the resin at the die outlet and enables more stable granulation. From the viewpoint, it is preferably 20 ° C. or lower, more preferably 18 ° C. or lower, further preferably 15 ° C. or lower, and further preferably 12 ° C. or lower.
By flowing the refrigerant of the multitubular heat exchanger into the interior, the soft resin passing through the refrigerant is cooled, that is, in the multitubular heat exchanger, due to its structure, the refrigerant inlet viscosity and A difference occurs between the outlet viscosity and the soft polyolefin resin that passes through this, resulting in local temperature unevenness, resulting in a temperature difference in the soft resin extruded from the die hole, and stability of granulation. Was found to decrease.
Therefore, the present inventors suppress the local temperature unevenness of the soft resin passing through the ratio of the outlet temperature and the inlet temperature of the refrigerant circulating in the multi-tube heat exchanger within a predetermined range. It has been found that a soft resin granulation method is provided that suppresses cutting defects sufficiently and enables more stable granulation. The difference between the outlet temperature and the inlet temperature of the refrigerant can be controlled by adjusting the flow rate of the refrigerant.

In the granulation method of the present invention, a multitubular heat exchanger is used. By using a multitubular and multitubular heat exchanger, it is possible to provide a granulation method of a soft resin capable of stable granulation while having a simple apparatus configuration. It is preferable that a static mixer is provided in the tube through which the soft resin of the multi-tube heat exchanger passes.
In the granulation method of the present invention, the flow path length / body diameter ratio (L / D ratio) of the multitubular heat exchanger can be appropriately set, but is preferably 2 to 10, more preferably 3 to 9, More preferably, it is 4-8.

[Soft resin]
Next, a soft resin to which the granulation method of the present invention can be applied will be described.
The tensile elastic modulus of the soft resin is preferably 1 to 200 MPa, more preferably 5 to 150 MPa, and still more preferably 10 to 100 MPa (a value measured according to JIS K 7113). Further, the melt flow rate (hereinafter also referred to as “MFR”) of the soft resin under the conditions of a temperature of 230 ° C. and a load of 21.18 N is preferably 1 to 10,000 g / 10 minutes, more preferably 3 to 5,000 g. / 10 minutes, more preferably 5 to 3,000 g / 10 minutes (measured according to JIS K7210).
In addition, the measuring method of a tensile elasticity modulus and MFR is as having described below.

(Measurement of tensile modulus)
In accordance with JIS K 7113, the tensile elastic modulus is measured under the following conditions.
-Test piece (No. 2 dumbbell) Thickness: 1mm
・ Crosshead speed: 100mm / min ・ Load cell: 100N
・ Measurement temperature: 23 ℃

[Measurement of melt flow rate (MFR)]
Measured in accordance with JIS K7210 under conditions of a temperature of 230 ° C. and a load of 21.18N.

Here, the soft resin to which the granulation method of the present invention can be applied is not particularly limited, but a soft polyolefin resin obtained by polymerizing an α-olefin having 3 to 28 carbon atoms using a metallocene catalyst (hereinafter referred to as “metallocene”). It can also be preferably applied to a "system soft polyolefin resin".
The viscosity of soft resin changes greatly due to temperature unevenness in the multi-tubular heat exchanger. As a result, the flow rate in the tube tends to be uneven and the problem of impaired stable granulation occurs. To do. Therefore, the effect of the present invention can be remarkably obtained.

More specific examples of the soft resin used in the granulation method of the present invention include the following.
[Olefin polymer]
The olefin polymer used as a soft resin is obtained by using a differential scanning calorimeter (DSC), holding the sample at −10 ° C. for 5 minutes in a nitrogen atmosphere, and then raising the temperature at 10 ° C./min. It is preferable that the melting endotherm (ΔH−D) obtained from the melting endotherm curve is 1 to 80 J / g.
The olefin polymer of the present invention is preferably an olefin polymer obtained by polymerizing one or more monomers selected from ethylene and an α-olefin having 3 to 28 carbon atoms.
Examples of the α-olefin having 3 to 28 carbon atoms include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-undecene and 1-dodecene. 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-icocene and the like. Among these, Preferably it is C3-C24 alpha-olefin, More preferably, it is C3-C12 alpha-olefin, More preferably, it is C3-C6 alpha-olefin, More preferably, it is C3-C4 Α-olefin, more preferably propylene. An olefin polymer obtained by polymerizing one of these alone may be used, or an olefin copolymer obtained by copolymerizing two or more of them may be used. In the present invention, the term “olefin polymer” simply includes an olefin copolymer.
Examples of the olefin polymer include an ethylene polymer in which 50 mol% or more of the monomer constituting the polymer is an ethylene monomer, a propylene polymer in which 50 mol% or more of the monomer constituting the polymer is a propylene monomer, Examples include butene-based polymers in which 50 mol% or more of the monomers constituting the coalescence are butene monomers, and propylene-based polymers are more preferable.

Examples of the olefin polymer used in the present invention include propylene homopolymer, propylene-ethylene random copolymer, propylene-butene random copolymer, propylene-α-olefin random copolymer, propylene-ethylene-butene random. A propylene polymer selected from a copolymer, a propylene-ethylene block copolymer, a propylene-butene block copolymer, a propylene-α-olefin block copolymer, a propylene-α-olefin graft copolymer, etc. Preferably there is.
Further, in the propylene polymer, it is more preferable that 50 mol% or more of the monomers constituting the olefin polymer is a propylene monomer, and the propylene polymer is (i) and / or (ii). The polymer which satisfy | fills may be sufficient.
(I) The structural unit of ethylene is contained in excess of 0 mol% and 20 mol% or less.
(Ii) The structural unit of 1-butene is contained in an amount of more than 0 mol% and 30 mol% or less.

[Melting endotherm (ΔH−D)]
The melting endotherm (ΔH-D) of the olefin polymer and the propylene polymer is preferably 1 to 80 J / g, more preferably 10 to 70 J / g, still more preferably 20 to 60 J / g, and further Preferably it is 20-50 J / g.
In the present invention, a differential scanning calorimeter (DSC-7, manufactured by Perkin Elmer Co., Ltd.) is used, and 10 mg of a sample is held at −10 ° C. for 5 minutes in a nitrogen atmosphere and then heated at 10 ° C./min. Calculated by calculating the area enclosed by the line (baseline) connecting the line part including the peak of the melting endotherm curve obtained by the above, the point on the low temperature side where there is no change in calorie, and the point on the high temperature side where there is no change in calorie Is done.

The crystallization time of the olefin polymer and the propylene polymer is preferably 1 minute or more, more preferably 3 minutes or more, still more preferably 5 minutes or more, and still more preferably 10 minutes or more.
The half crystallization time was measured by using a differential scanning calorimeter, and after the sample was melted at 190 ° C. for 3 minutes in a nitrogen atmosphere, liquefied nitrogen was introduced and rapidly (about 300 ° C./min) 25 ° C. This is the time from when the sample temperature reaches 25 ° C. until the crystallization exothermic peak is observed.

The propylene polymer used in the present invention is preferably a propylene polymer satisfying at least one of the following (1) and (2), more preferably satisfying the following (3) and (4): More preferably, the following (5) and (6) are further satisfied, and further preferably, the following (7) is further satisfied.
(1) [mmmm] is 20 to 60 mol%.
(2) Using a differential scanning calorimeter (DSC), hold the sample at −10 ° C. for 5 minutes in a nitrogen atmosphere, and then raise the temperature at 10 ° C./min. The melting point (Tm-D) defined as the observed peak top is 0-120 ° C.
(3) [rrrr] / (1- [mmmm]) ≦ 0.1
(4) Molecular weight distribution (Mw / Mn) <4.0
(5) [rmrm]> 2.5 mol%
(6) [mm] × [rr] / [mr] ² ≦ 2.0
(7) The weight average molecular weight (Mw) is 20,000 to 1,000,000.

(1) Mesopentad fraction [mmmm]
The mesopentad fraction [mmmm] is an index representing the stereoregularity of the propylene-based polymer, and the stereoregularity increases as the mesopentad fraction [mmmm] increases. [Mmmm] is preferably 25 to 55 mol%, more preferably 30 to 50 mol%, still more preferably 40 to 50 mol%.

(2) Melting point (Tm-D)
The melting point (Tm-D) of the propylene polymer is preferably higher from the viewpoints of strength and moldability. The said melting | fusing point (Tm-D) becomes like this. Preferably it is 0-120 degreeC, More preferably, it is 50-100 degreeC, More preferably, it is 55-90 degreeC, More preferably, it is 60-80 degreeC.
In the present invention, a differential scanning calorimeter (DSC-7, manufactured by Perkin Elmer Co., Ltd.) is used, and 10 mg of a sample is held at −10 ° C. for 5 minutes in a nitrogen atmosphere and then heated at 10 ° C./min. The peak top of the peak observed on the highest temperature side of the melting endothermic curve obtained by the above is defined as the melting point (Tm-D). The melting point can be controlled by appropriately adjusting the monomer concentration and reaction pressure.

(3) [rrrr] / (1- [mmmm])
The value of [rrrr] / (1- [mmmm]) is obtained from the mesopentad fraction [mmmm] and the racemic pentad fraction [rrrr] and is an index indicating the uniformity of the regularity distribution of polypropylene. When this value of [rrrr] / (1- [mmmm]) increases, it becomes a mixture of highly stereoregular polypropylene and atactic polypropylene like conventional polypropylene produced using existing catalyst systems, which causes stickiness. . In the above, [rrrr] and [mmmm] are ratios (mol% / 100).
The value of [rrrr] / (1- [mmmm]) in the propylene-based polymer is preferably 0.1 or less, more preferably 0.001 to 0.05, and still more preferably 0.00 from the viewpoint of stickiness. It is 001-0.04, More preferably, it is 0.01-0.04.

Here, the mesopentad fraction [mmmm], the racemic pentad fraction [rrrr], and the racemic mesoracemi mesopentad fraction [rmrm] to be described later are determined according to “Macromolecules, 6, 925 (1973) ”, and meso fraction, racemic fraction, and racemic meso-racemic meso in pentad units in the polypropylene molecular chain measured by the methyl group signal of the ¹³ C-NMR spectrum. It is a fraction. As the mesopentad fraction [mmmm] increases, the stereoregularity increases. Further, triad fractions [mm], [rr] and [mr] described later are also calculated by the above method.

(4) Molecular weight distribution (Mw / Mn)
The molecular weight distribution (Mw / Mn) of the propylene-based polymer is preferably less than 4 from the viewpoint of high strength. The molecular weight distribution (Mw / Mn) of the olefin polymer and the propylene polymer is preferably 3 or less, more preferably 2.5 or less, and further preferably 1.5 to 2.5.
In the present invention, the molecular weight distribution (Mw / Mn) is a value calculated from the polystyrene-equivalent weight average molecular weight Mw and number average molecular weight Mn measured by gel permeation chromatography (GPC).

(5) Racemic meso racemic meso pentad fraction [rmrm]
The racemic meso racemic meso pentad fraction [rmrm] is an index representing the randomness of the stereoregularity of polypropylene, and the randomness of polypropylene increases as the value increases.
The racemic meso racemic meso pentad fraction [rmrm] of the propylene-based polymer is preferably more than 2.5 mol%, more preferably 2.6 mol% or more, still more preferably 2.7 mol% or more. And preferably 10 mol% or less, more preferably 7 mol% or less, still more preferably 5 mol% or less, still more preferably 4 mol% or less.

(6) [mm] × [rr] / [mr] ²
The value of [mm] × [rr] / [mr] ² calculated from the triad fraction [mm], [rr] and [mr] represents an index of randomness of the polymer. Becomes higher. The propylene polymer used in the present invention has a value of the above formula of usually 2 or less, preferably 1.8 to 0.5, and more preferably 1.5 to 0.5.

(7) Weight average molecular weight (Mw)
The weight average molecular weight (Mw) is preferably 20,000 to 1,000,000, more preferably 50,000 to 800,000, still more preferably 80,000 to 500,000. The weight average molecular weight (Mw) is a value in terms of polystyrene measured by a gel permeation chromatography (GPC) method.

As the propylene polymer, for example, a propylene homopolymer can be produced using a metallocene catalyst and propylene as described in WO2003 / 087172. In particular, those using a transition metal compound in which a ligand forms a cross-linked structure via a cross-linking group are preferred, and in particular, a transition metal compound that forms a cross-linked structure via two cross-linking groups and Metallocene catalysts obtained by combining promoters are preferred.
For example,
(I) General formula (I):

[In the formula, M represents a group 3-10 of the periodic table or a lanthanoid series metal element, and E ¹ and E ² represent a substituted cyclopentadienyl group, an indenyl group, a substituted indenyl group, a heterocyclopentadienyl group, respectively. A ligand selected from a substituted heterocyclopentadienyl group, an amide group, a phosphide group, a hydrocarbon group, and a silicon-containing group, which forms a cross-linked structure via A ¹ and A ² In addition, they may be the same or different from each other, X represents a σ-bonded ligand, and when there are a plurality of X, the plurality of X may be the same or different, and other X, E ¹ , E ² or Y may be cross-linked. Y represents a Lewis base, and when there are a plurality of Y, the plurality of Y may be the same or different, and may be cross-linked with other Y, E ¹ , E ² or X, and A ¹ and A ² are A divalent bridging group that binds two ligands, a hydrocarbon group having 1 to 20 carbon atoms, a halogen-containing hydrocarbon group having 1 to 20 carbon atoms, a silicon-containing group, a germanium-containing group, a tin-containing group _{, -O -, - CO -,} - S -, - SO 2 -, - Se -, - NR 1 -, - PR 1 -, - P (O) R 1 -, - BR 1 - or -AlR ¹ - R ¹ represents a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 20 carbon atoms, or a halogen-containing hydrocarbon group having 1 to 20 carbon atoms, which may be the same as or different from each other. q represents an integer of 1 to 5 and represents [(M valence) -2], and r represents an integer of 0 to 3. ]
(Ii) (ii-1) a compound capable of reacting with the transition metal compound of component (i) or a derivative thereof to form an ionic complex, and (ii-2) And a polymerization catalyst containing at least one component selected from aluminoxane.

  As the transition metal compound (i), a ligand is preferably a (1,2 ′) (2,1 ′) double-bridged transition metal compound, such as (1,2′-dimethylsilylene) ( 2,1'-dimethylsilylene) -bis (3-trimethylsilylmethylindenyl) zirconium dichloride.

  Specific examples of the compound of component (ii-1) include triethylammonium tetraphenylborate, tri-n-butylammonium tetraphenylborate, trimethylammonium tetraphenylborate, tetraethylammonium tetraphenylborate, methyl tetraphenylborate (tri- n-butyl) ammonium, benzyl tetraphenylborate (tri-n-butyl) ammonium, dimethyldiphenylammonium tetraphenylborate, triphenyl (methyl) ammonium tetraphenylborate, trimethylanilinium tetraphenylborate, methylpyridinium tetraphenylborate, tetra Benzylpyridinium phenylborate, methyl tetraphenylborate (2-cyanopyridinium), trikis (tetrafluorophenyl) borate triethyla Monium, tetrakis (pentafluorophenyl) tri-n-butylammonium borate, tetrakis (pentafluorophenyl) triphenylammonium borate, tetrakis (pentafluorophenyl) tetra-n-butylammonium borate, tetraethylammonium tetrakis (pentafluorophenyl) borate Benzyl tetrakis (pentafluorophenyl) ammonium borate (tri-n-butyl), methyldiphenylammonium tetrakis (pentafluorophenyl) borate, triphenyl (methyl) ammonium tetrakis (pentafluorophenyl) borate, tetrakis (pentafluorophenyl) boric acid Methylanilinium, tetrakis (pentafluorophenyl) borate dimethylanilinium, tetrakis (pentafluoropheny L) Trimethylanilinium borate, methyl pyridinium tetrakis (pentafluorophenyl) borate, benzyl pyridinium tetrakis (pentafluorophenyl) borate, methyl tetrakis (pentafluorophenyl) borate (2-cyanopyridinium), benzyl tetrakis (pentafluorophenyl) borate (2-cyanopyridinium), methyl tetrakis (pentafluorophenyl) borate (4-cyanopyridinium), triphenylphosphonium tetrakis (pentafluorophenyl) borate, tetrakis [bis (3,5-ditrifluoromethyl) phenyl] dimethylaniline borate Ferrocenium tetraphenylborate, silver tetraphenylborate, trityl tetraphenylborate, tetraphenylporphyrin manganese tetraphenylborate, Trakis (pentafluorophenyl) borate ferrocenium, tetrakis (pentafluorophenyl) borate (1,1′-dimethylferrocenium), tetrakis (pentafluorophenyl) decamethylferrocenium borate, tetrakis (pentafluorophenyl) silver borate, Tetrakis (pentafluorophenyl) triborate borate, tetrakis (pentafluorophenyl) lithium borate, tetrakis (pentafluorophenyl) sodium borate, tetrakis (pentafluorophenyl) borate tetraphenylporphyrin manganese, silver tetrafluoroborate, silver hexafluorophosphate, hexa Examples thereof include silver fluoroarsenate, silver perchlorate, silver trifluoroacetate, and silver trifluoromethanesulfonate.

  Examples of the aluminoxane as the component (ii-2) include known chain aluminoxanes and cyclic aluminoxanes.

  Trimethylaluminum, triethylaluminum, triisopropylaluminum, triisobutylaluminum, dimethylaluminum chloride, diethylaluminum chloride, methylaluminum dichloride, ethylaluminum dichloride, dimethylaluminum fluoride, diisobutylaluminum hydride, diethylaluminum hydride, ethylaluminum sesquichloride, etc. These organoaluminum compounds may be used in combination to produce a propylene polymer.

[Other soft resins]
Similarly, examples of propylene polymers produced with metallocene catalysts include copolymers of propylene and ethylene (such as vistamaxx manufactured by Exxon Mobel), and copolymers of ethylene and octene (such as Engage manufactured by Dow Chemical). , Propylene and ethylene, butene copolymer (Degussa Bestplast etc.) and the like.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the following drawings.
FIG. 1 is a diagram schematically showing a basic configuration of an apparatus according to a first embodiment used in the present invention. FIG. 2 is a cross-sectional view schematically showing the basic configuration of a multi-tube heat exchanger used in the present invention. FIG. 3 is a diagram schematically showing the basic configuration of the apparatus of the second embodiment used in the present invention.

[First form]
The apparatus according to the first embodiment includes a melting tank 11 for melting a soft resin, a multi-tube heat exchanger 12 for lowering the temperature of the molten soft resin, a die 13 for discharging the lowered soft resin into a rod shape, An underwater cutting chamber 14 having a rotary blade 141 for cutting the soft resin discharged from the die in water, and a dehydrator 15 for taking out the soft resin granulated from the water are provided.

The multitubular heat exchanger 12 is a liquid refrigerant multitubular heat exchanger.
The multitubular heat exchanger 12 includes a preliminary chamber 122 having a resin inlet 121 into which a soft resin in a molten state is allowed to flow, and a resin collecting chamber 124 having a resin outlet 123 from which the soft resin whose temperature has been lowered is discharged. The refrigerant chamber 127 is provided between the preliminary chamber 122 and the resin collecting chamber 124, and has a refrigerant inlet 125 into which liquid refrigerant flows and a refrigerant outlet 126 into which the liquid refrigerant is discharged, and the refrigerant chamber 127. , A plurality of (for example, 14) hollow heat transfer tubes 128 that connect between the preliminary chamber 122 and the resin assembly chamber 124, and a plurality of (provided that the flow direction of the heat transfer tubes 128 is perpendicular to the flow direction. For example, six sheets of refrigerant guide plates 129 are provided.
In addition, it is preferable that a static mixer is provided in the heat transfer tube 128 to improve the cooling capacity (not shown).
The flow path length / body diameter ratio (L / D ratio) of the multitubular heat exchanger is preferably 2 to 10, more preferably 3 to 9, and further preferably 4 to 8. In the multitubular heat exchanger, the trunk diameter means the sum of the diameters of the provided heat transfer tubes, and the flow path length means the flow path length of the heat transfer tubes.

The granulation method of the present invention using the apparatus according to the first embodiment will be described.
In the granulation method of the present invention, for example, the soft resin is supplied to the melting tank 11 and is heated in the melting tank to obtain a soft resin in a molten state. The molten soft resin is sent to the multitubular heat exchanger 12, and the temperature of the soft resin is lowered by the multitubular heat exchanger.

  In the multitubular heat exchanger 12, the soft resin flows from the resin inlet 121 and is sent from the preliminary chamber 122 to the plurality of heat transfer tubes 128. Thereafter, the temperature of the soft resin is lowered in each heat transfer tube 128, and then merges in the resin collecting chamber 124 and is discharged from the resin discharge port 123.

The ratio of the viscosity of the soft resin at the resin inlet 121 of the multi-tube heat exchanger 12 and the viscosity of the soft resin at the resin outlet 123 is the ratio of the outlet viscosity and the inlet viscosity shown above. Is preferred.
The difference between the outlet temperature and the inlet temperature of the refrigerant flowing through the multitubular heat exchanger 12 is preferably 10 ° C. from the viewpoint of reducing the temperature difference of the resin in the radial direction and performing more significantly stable granulation. Hereinafter, it is more preferably 7 ° C. or less, and further preferably 5 ° C. or less.

The soft resin lowered in temperature by the multi-tube heat exchanger 12 is sent to the die 13 and discharged from the die into the cooling water in the cutting chamber 14 as a plurality of rod-shaped resins.
In the cutting chamber 14, the rotary blade 141 rotates at a high speed to cut the resin. Further, cooling water W is caused to flow in the cutting chamber 14, and the cut pellets are conveyed from the chamber 14 to the dehydrator 15 by the cooling water. Then, the pellet resin and the cooling water are separated by the dehydrator 15.

The temperature of the cooling water in the underwater granulation is preferably 30 ° C. or less, more preferably 20 ° C. or less, still more preferably 15 ° C. or less, and preferably 3 ° C. or more. The temperature of the cooling water can be adjusted by heating or cooling with a heat medium cooler or a heat medium heater (not shown).
The cooling water preferably contains an anti-fusing agent. Examples of the anti-fusing agent include silicone. The content of the anti-fusing agent is preferably 100 to 5000 ppm by mass, more preferably 500 to 1000 ppm by mass with respect to the cooling water.

  The peripheral speed of the rotary blade in the cutting chamber is preferably 1 to 20 m / s, more preferably 1 to 10 m / s.

[Second form]
The device according to the second embodiment basically has the same configuration as the device according to the first embodiment. The common configurations are denoted by the same reference numerals as those in the first embodiment in FIG. 3, and detailed descriptions thereof are omitted.
The apparatus according to the second embodiment further includes a static mixer 16 between the multi-tube heat exchanger 12 and the die 13. The soft resin sent from the multi-tube heat exchanger 12 is mixed in a static mixer, and the outlet temperature difference of the sent soft resin can be reduced. That is, by providing the static mixer 16, it becomes possible to reduce the temperature difference of the soft resin near the die outlet, and stable granulation can be performed.

[Soft resin pellets]
As described above, the granulated soft resin (hereinafter also referred to as “soft resin pellet”) is obtained by the production method of the present invention.
The tensile elastic modulus of the soft resin pellet is preferably 1 to 200 MPa, more preferably 5 to 150 MPa, and still more preferably 10 to 100 MPa.
The tensile elastic modulus is measured according to JIS K7113.
The melt flow rate (MFR) of the soft resin pellet at a temperature of 230 ° C. and a load of 21.18 N is preferably 1 to 10,000 g / 10 minutes, more preferably 3 to 5,000 g / 10 minutes, and still more preferably 5 ~ 3,000 g / 10 min.
The melt flow rate (MFR) is measured according to JIS K7210.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples. The physical properties of the soft resin were measured by the following method.

[DSC measurement]
Using a differential scanning calorimeter (DSC-7, manufactured by Perkin Elmer Co.), a melting endotherm obtained by holding 10 mg of a sample at −10 ° C. for 5 minutes in a nitrogen atmosphere and then raising the temperature at 10 ° C./min. It calculated | required as melting endotherm (DELTA) HD from a curve. Moreover, melting | fusing point (Tm-D) was calculated | required from the peak top of the peak observed on the highest temperature side of the obtained melting endothermic curve.
The melting endotherm (ΔH-D) is a differential scanning calorimeter (manufactured by Perkin Elmer Co., Ltd.) with a line connecting a point on the low temperature side where there is no change in heat quantity and a point on the high temperature side where there is no change in heat quantity as the baseline. , DSC-7), and calculating the area surrounded by the line portion including the peak of the melting endothermic curve obtained by DSC measurement and the base line.

[Weight average molecular weight (Mw), molecular weight distribution (Mw / Mn) measurement]
The weight average molecular weight (Mw) and the number average molecular weight (Mn) were measured by gel permeation chromatography (GPC) method to determine the molecular weight distribution (Mw / Mn). For the measurement, the following equipment and conditions were used, and polystyrene-reduced weight average molecular weight and number average molecular weight were obtained. The molecular weight distribution (Mw / Mn) is a value calculated from these weight average molecular weight (Mw) and number average molecular weight (Mn).
<GPC measurement device>
Column: “TOSO GMHHR-H (S) HT” manufactured by Tosoh Corporation
Detector: RI detection for liquid chromatogram "WATERS 150C" manufactured by Waters Corporation
<Measurement conditions>
Solvent: 1,2,4-trichlorobenzene Measurement temperature: 145 ° C
Flow rate: 1.0 ml / min Sample concentration: 2.2 mg / ml
Injection volume: 160 μl
Calibration curve: Universal Calibration
Analysis program: HT-GPC (Ver.1.0)

[NMR measurement]
The ¹³ C-NMR spectrum was measured using the following apparatus and conditions. In addition, the attribution of the peak followed the method proposed by A. Zambelli et al. In “Macromolecules, 8, 687 (1975)”.
Apparatus: JNM-EX400 type ¹³ C-NMR apparatus manufactured by JEOL Ltd. Method: Proton complete decoupling method Concentration: 220 mg / ml
Solvent: 90:10 (volume ratio) mixed solvent of 1,2,4-trichlorobenzene and heavy benzene Temperature: 130 ° C
Pulse width: 45 °
Pulse repetition time: 4 seconds Integration: 10,000 times

<Calculation formula>
M = m / S × 100
R = γ / S × 100
S = Pββ + Pαβ + Pαγ
S: Signal intensity of side chain methyl carbon atoms of all propylene units Pββ: 19.8 to 22.5 ppm
Pαβ: 18.0 to 17.5 ppm
Pαγ: 17.5 to 17.1 ppm
γ: Racemic pentad chain: 20.7 to 20.3 ppm
m: Mesopentad chain: 21.7-22.5 ppm

The mesopentad fraction [mmmm], the racemic pentad fraction [rrrr] and the racemic mesoracemi mesopentad fraction [rmrm] are described in “Macromolecules, 6, 925 (1973)” by A. Zambelli et al. The meso fraction, the racemic fraction, and the racemic meso-racemic meso in the pentad unit in the polypropylene molecular chain measured by the methyl group signal in the ¹³ C-NMR spectrum were obtained according to the proposed method. It is a fraction. As the mesopentad fraction [mmmm] increases, the stereoregularity increases. The triad fractions [mm], [rr] and [mr] were also calculated by the above method.

[Melt flow rate (MFR) measurement]
Based on JIS K7210, the measurement was performed under conditions of a temperature of 230 ° C. and a load of 2.16 kg.

[Semi-crystallization time]
The half crystallization time was measured using a differential scanning calorimeter (“DSC-7” manufactured by Perkin Elmer).

[Viscosity (190 ° C)]
The melt viscosity at 190 ° C. was measured with a Brookfield B-type viscometer (model: HADV-E, model number: KN3312442).

[Tensile modulus]
The tensile elastic modulus was measured under the following conditions based on JIS K7113.
Test piece: No. 2 dumbbell (thickness: 1 mm)
Crosshead speed: 100mm / min Load cell: 100N
Measurement temperature: 23 ° C

Production Example 1 [Production of Polypropylene Polymer (PP1)]
In a stainless steel reactor having an internal volume of 20 L with a stirrer, n-heptane was 20 L / hr, triisobutylaluminum was 15 mmol / hr, dimethylanilinium tetrakispentafluorophenylborate, and (1,2'-dimethylsilylene) A catalyst component obtained by contacting (2,1′-dimethylsilylene) -bis (3-trimethylsilylmethylindenyl) zirconium dichloride, triisobutylaluminum and propylene in a mass ratio of 1: 2: 20 in advance is used as zirconium. It was continuously supplied at a conversion of 30 μmol / hr.
Propylene and hydrogen are continuously fed under conditions where the ratio of hydrogen is much smaller than that of Production Example 1 so as to keep the total pressure in the reactor at 1.0 MPa · G, and the polymerization temperature is appropriately adjusted around 70 ° C. to obtain a desired molecular weight A polymerization solution having was obtained.
To the obtained polymerization solution, an antioxidant was added so that the content ratio was 1000 mass ppm, and then n-heptane as a solvent was removed to obtain a polypropylene polymer (PP1).

  The polypropylene polymer (PP1) obtained in Production Example 1 was measured as described above (weight average molecular weight Mw 120,000, Mw / Mn: 2.1, ΔH-D: 27.5 J / g). The other results are shown in Table 1 below.

Production Example 2
A polypropylene polymer was obtained in the same manner as in Production Example 1 except that the polymerization temperature was changed from 70 ° C to 71 ° C.

Example 1 Polypropylene Granulation Method The polypropylene polymer obtained in Production Example 1 was desolvated at an internal temperature of 180 ° C. using a stainless steel melting tank having an internal volume of 3 m ³ .
Thereafter, the molten resin was transferred to a multi-tube heat exchanger (manufactured by Noritake Company Limited, L / D ratio = 4) with a transfer pump. The soft resin was cooled to 126 ° C. with a multitubular heat exchanger and then granulated in water with a granulator. Details of the cooling conditions are shown in Table 1. As the granulator, PASC-21HS manufactured by Tanabe Plastics Machine Co., Ltd. was used, the cooling water temperature was 10 ° C., and the peripheral speed of the cutter was 3.8 m / s. Moreover, silicone (Shin-Etsu Chemical Co., Ltd. product, X-22-904) was added to cooling water so that it might become 600 mass ppm.
As a result of granulation in water, stable granulation of polypropylene pellets was possible without the discharged soft resin being wrapped around the rotary blade in the above granulation method.

Example 2
Except that the "polypropylene polymer obtained in Production Example 1" was "polypropylene polymer obtained in Production Example 2" and the cooling conditions in the multi-tube heat exchanger were as shown in Table 2, Granulation of Example 2 was carried out under the same conditions as in Example 1. As a result of granulation in water, stable granulation of polypropylene pellets was possible without the discharged soft resin being wrapped around the rotary blade in the above granulation method.

  According to the present invention, a method for granulating a soft resin capable of stable granulation can be provided, and therefore, it can be applied to industrial production of soft resin pellets.

11: Melting tank 12: Multi-tube heat exchanger 13: Die 14: Underwater cutting chamber 141: Rotary blade 15: Dehydrator 16: Static mixer W: Cooling water

Claims (9)

The soft resin is in a molten state,
Next, after the temperature of the soft resin is lowered using a multi-tubular heat exchanger, the soft resin is discharged from a die outlet, cut with a rotary blade in water, and granulated in water. Granulation method.   The granulation method of a soft resin according to claim 1, wherein the temperature is lowered to a temperature at which the soft resin has a viscosity of 30 Pa · s or more in the multi-tube heat exchanger.   The method for granulating a soft resin according to claim 1 or 2, wherein the temperature difference of the soft resin in the radial direction at the die outlet is 10 ° C or less.   The method for granulating a soft resin according to any one of claims 1 to 3, wherein a ratio of the outlet viscosity and the inlet viscosity of the soft resin in the multitubular heat exchanger is 20 or less.   The method for granulating a soft resin according to any one of claims 1 to 4, wherein a difference between an outlet temperature and an inlet temperature of the refrigerant flowing through the multi-tube heat exchanger is 20 ° C or less.   The method for granulating a soft resin according to any one of claims 1 to 5, wherein the multi-tubular heat exchanger includes a static mixer in a pipe through which the soft resin passes.   The flow path length / body diameter ratio (L / D ratio) of the multi-tubular heat exchanger is 2 to 10, 7. The soft resin granulation method according to any one of claims 1 to 6. The method for granulating a soft resin according to any one of claims 1 to 7, wherein the soft resin is a propylene polymer satisfying at least one of (1) and (2).
(1) [mmmm] is 20 to 60 mol%.
(2) Using a differential scanning calorimeter (DSC), hold the sample at −10 ° C. for 5 minutes in a nitrogen atmosphere, and then raise the temperature at 10 ° C./min. The melting point (Tm-D) defined as the observed peak top is 0-120 ° C.   The tensile elastic modulus of the soft resin is 1 to 200 MPa, and the melt flow rate (MFR) of the soft resin under conditions of a temperature of 230 ° C. and a load of 21.18 N is 1 to 10,000 g / 10 minutes. Item 9. The method for granulating a soft resin according to any one of Items 1 to 8.