JP5023479B2 - Post-treatment method for polyolefin pellets - Google Patents

Description

  The present invention relates to a post-treatment method for polyolefin pellets having adhesiveness. More specifically, when the polyolefin pellets having adhesive properties are air-fed, post-treatment of the polyolefin pellets that can reduce the air-fed pressure loss and prevent the pellets from being bitten into the rotary valve installed in the air-fed pipe. It is about the method.

  In the case of pellets of resin such as rubber and resin of olefin copolymer having tackiness, the mutual adhesion of pellets during silo storage or storage after filling has been a problem in the past, and various countermeasures have been taken. For example, a method of mixing talc, silica, calcium carbonate, higher fatty acid, etc. as an antiblocking agent (anti-adhesive agent) on the pellet surface of an olefin copolymer rubber or polyolefin copolymer (see, for example, Patent Documents 1 and 2) . A method in which resin pellets are introduced into a transport pipe, an anti-blocking powder slurry is introduced into the transport pipe, the pellet surface is coated with powder, and the resin pellets are dried while circulating through a hopper (see Patent Document 3). There is a method in which a resin strand is passed through a container filled with an aqueous dispersion release agent composition, and then pelletized and dried (see Patent Document 4).

  On the other hand, in the polyolefin production process, adhesive resin pellets have high pressure loss in the piping when the pellets are air-fed, and the rotary valve blades installed in the middle of the air-feeding piping or in the silo receiving part or discharging part There is a problem that pellets are easily caught between casings, and further improvement is required from the viewpoint of process rationalization such as blower capacity for air transportation, capacity of drive motor of rotary valve, long distance transportation capacity by air transportation. It was.

(Japanese Patent Laid-Open No. 56-136347, pages 1 to 2) (JP-A-59-124829, pages 1 to 2) (Japanese Patent Publication No. 7-37026, pages 1 to 3) (JP-A-9-77890, pages 1 to 3)

  Under such circumstances, in the post-treatment step in the polyolefin production process, the present invention reduces pressure loss in the air feed piping of the polyolefin pellets having adhesiveness, and bites the pellet into the rotary valve attached in the air feed piping. It aims at providing the post-processing method of the polyolefin pellet which can perform prevention.

That is, the present invention
(1) In a post-treatment process comprising a granulation process, an air transport process and a silo storage process of a polyolefin production process, an operation of uniformly adhering an antiblocking agent to the surface of the polyolefin pellets is performed, and the polyolefin is obtained by performing the operation. A post-treatment method for polyolefin pellets, characterized by reducing the air pressure loss of pellets and preventing biting between the blade and casing of the rotary valve;
(2) The post-treatment method for polyolefin pellets according to (1), wherein the operation of uniformly attaching the antiblocking agent to the surface of the polyolefin pellets is performed at a plurality of locations in the polyolefin pellet air feeding step,
(3) The polyolefin according to (1) or (2) above, wherein the operation of uniformly adhering the antiblocking agent to the surface of the polyolefin pellet is performed by spraying the antiblocking agent in the polyolefin pellet emptying step. Pellet post-treatment method,
(4) The operation of uniformly adhering an antiblocking agent to the surface of the polyolefin pellets is performed by adding an antiblocking agent to circulating water used for watering the polyolefin pellets in the granulation step (1) ) To a post-treatment method for polyolefin pellets according to any one of (3),
(5) The operation of uniformly attaching the anti-blocking agent to the surface of the polyolefin pellets is performed when the polyolefin pellets pass through the rotary valve and while being sent by air, while the anti-blocking agent is attached to the surface of the polyolefin pellets relative to the weight of the polyolefin pellets. The post-treatment method for polyolefin pellets according to any one of (1) to (4), wherein the concentration is 500 to 10,000 ppm by weight,
(6) The polyolefin pellet is a copolymer resin pellet of a comonomer selected from vinyl acetate, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate and glycidyl methacrylate and ethylene (1) ) To the polyolefin pellet post-treatment method according to any one of (5),
(7) Any of the above (1) to (6), wherein the antiblocking agent is any one selected from talc, ethylene-vinyl acetate copolymer, modified polyolefin, or a mixture thereof. This relates to a post-treatment method for polyolefin pellets.

  According to the present invention, in a post-processing step in a polyolefin production process, pressure loss in an air-feeding piping of an adhesive polyolefin pellet is reduced, and pellets to a rotary valve installed in the air-feeding piping or in a silo receiving part or discharging part It has become possible to provide a post-treatment method for polyolefin pellets that can prevent the occurrence of biting.

  The outline of the polyolefin production process after the granulation step is shown in FIG. The granulation step includes an extruder c, a circulating water pump d, a circulating water tank e, a centrifugal dryer f, a vibrating sieve g, and the like. The air sending process includes an air sending blower (not shown), an air sending pipe i-1 to 3, a rotary valve h-1 to 4, a blender j, an intermediate silo k, a filling silo 1 and the like. The pellets are stored and filled in a silo storage process consisting of a large number of silo groups (not shown except k and l). In the present invention, these steps are collectively referred to as post-processing steps.

  The molten polyolefin after polymerization or one or more polyolefin pellets, or a mixture obtained by adding one or more additives thereto, is processed into pellets in the granulation step. At that time, until the silo storage process where the filling operation is finally performed, the pressure loss in the air sending pipe during air sending over a long distance and the blade and casing of the rotary valve attached to the intermediate silo existing in the middle It is necessary to relieve the load on the rotary valve drive motor due to the intercalation of the pellets. Then, it turned out that there exists a favorable effect, when operation which makes an antiblocking agent adhere uniformly to the pellet surface was performed.

  That is, by performing an operation of spraying the anti-blocking agent at least at a plurality of locations of the piping in the air feeding process, it is possible to reduce the air pressure loss of polyolefin pellets and the phenomenon of biting into the rotary valve. It was. Furthermore, a uniform antiblocking agent layer can be formed on the surface of the pellets more effectively by adding the antiblocking agent into the circulating water tank that carries the underwater cut pellets in the granulation step.

  The anti-blocking agent can be sprayed into the pipe either by installing an anti-blocking agent spray nozzle in the diameter direction of the pipe or by inclining the pipe in the direction of the pellet flow or in the opposite direction. The anti-blocking agent can be uniformly adhered to the pellet. The spray nozzle sprays the anti-blocking agent emulsion together with air into a 6-inch air feed pipe through a thin pipe of about 1/2 inch. The anti-blocking agent is appropriately dried and uniformly adheres to the pellet surface by the temperature in the pipe (about 25 to 60 ° C.).

  As the type of the antiblocking agent, talc, ethylene-vinyl acetate copolymer, modified polyolefin, or a mixture thereof is preferably used. The amount of the anti-blocking agent used is preferably such that the concentration of the anti-blocking agent attached to the polyolefin pellet surface with respect to the polyolefin pellet weight is 500 to 10,000 wtppm.

  The polyolefin pellet is particularly effective when used as a copolymer resin pellet of a comonomer selected from vinyl acetate, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, and glycidyl methacrylate.

EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example, this invention is not limited to these Examples from the first.
Example 1
Evaluation of air pressure loss at the time of pellet air transport The experiment based on the apparatus based on the flow chart of Fig. 1 is used to granulate the copolymerized molten polymer of ethylene and vinyl acetate into pellets and air transport them to the filling silo as follows. I went like that.
Add anti-blocking agent (Kemipearl V-200, manufactured by Mitsui Chemicals) from anti-blocking agent addition point X-1 to circulating water tank e so that the concentration of anti-blocking agent in circulating water is about 0.5 to 1.0 wt%. Then, an anti-blocking agent is added from the addition point X-2 to the pellets coming out of the vibrating sieve g, and the pellet surface anti-blocking agent concentration is adjusted to 500 to 1500 wtppm with respect to the pellet weight during air feeding, Pellet is fed by air blower via feed pipe i-1 (pipe inner diameter: 15.84 cm, pipe length: about 128 m), and passes through rotary valve h-1 (Japan Aluminum RA-GWW type). Later, it was accepted by blender j.
Table 1 shows the pressure loss coefficient β, which is an index for evaluating the air pressure loss up to the blender j, MFR (g / 10 min), vinyl acetate, which is a measure of the adhesiveness of the ethylene vinyl acetate copolymer used in the experiment. This is shown together with other contents (hereinafter abbreviated as VA content, wt%) and other experimental conditions.
The pressure loss coefficient β, which is an index for evaluating the air pressure loss, was calculated by the following equation (1).
ΔP = ΔP _air (1 + mβ) (1)
ΔP: Pressure loss during air transportation, ΔP _air : Pressure loss when only air is passed through the air transportation piping, m: Solid-gas ratio of pellet and air, β: Pressure loss coefficient

  The ethylene vinyl acetate copolymers used in Experiment Nos. 1 and 3 and Experiment Nos. 2 and 4 have almost the same MFR and VA contents, respectively, so that the pellet tackiness is almost the same. When comparing these, the pressure loss coefficient β of the experiment numbers 1 and 2 to which the anti-blocking agent was added was 0.320 and 0.580, and the pressure loss coefficient β of the experiment numbers 3 and 4 to which the anti-blocking agent was not added was 1.55 and 3.00, and it was found that the pressure loss during pellet emptying was greatly reduced by the addition of the antiblocking agent.

  Although the pressure loss coefficient β was not calculated, the pellet was discharged from the blender j by a rotary valve h-2 (Nihon Aluminum RA-GWW type), and the antiblocking agent (Chemipearl) was added from the antiblocking agent addition point X-3. V-200 Mitsui Chemicals Co., Ltd.) is adjusted so that the pellet surface antiblocking agent concentration is 500 to 1500 wtppm with respect to the pellet weight during the air transportation, and the filling silo through the air transportation pipe i-2 to 3 and the intermediate silo k sent to l. As a result, it was possible to achieve air feeding with a low pressure loss as in the case of blender j.

Example 2
Evaluating the effect of the rotary valve on the pellets between the blade and the casing Using the same air-feed route as in Example 1, 100 tons or more of ethylene and vinyl acetate copolymer polyolefin pellets were added to the rotary valves h-1 to 4 ( Air transport was carried out while passing through Japan Aluminum RA-GWW type). However, as the VA content is higher, the stickiness of the pellet is also increased. Therefore, the antiblocking agent addition concentration and type added at the antiblocking agent addition points X-1 to 3 are changed as shown in Table 2 and then air-fed. Went.
The experimental results are shown in Experiment Nos. 1, 2, and 3 in Table 2. As a result, in Experiment Nos. 1 and 2, since the anti-blocking agent was added at the anti-blocking agent addition point X-1 to 3, the drive motor of any rotary valve did not exceed its rated amperage (10 to 20A). Stable operation was possible. On the other hand, in Experiment No. 3, in which no anti-blocking agent was added, the pellet was caught between the rotary valve blade and casing, and the trip exceeded the rated amperage of the rotary valve drive motor, so stable operation was possible. There wasn't.

* 1: ○ indicates Chemipearl V-200 (Mitsui Chemicals), and ● indicates Talcan powder PK-P (Hayashi Kasei talc).
* 2: Anti-blocking agent concentration (wt%) in circulating water
* 3: Antiblocking agent concentration (wtppm) on the pellet surface relative to the pellet weight during air transportation.

Flow chart showing the outline of the polyolefin manufacturing process after the granulation process

Explanation of symbols

a ... Raw polyolefin (polymerized molten polyolefin or pelleted polyolefin, etc.), b ... Raw material receiving hopper, c ... Extruder, d ... Circulating water pump, e ... Circulating water tank, f ... Centrifugal dryer, g ... Vibrating sieve , H-1 to 4 ... Rotary valve, i-1 to 3 ... Air feed piping, j ... Blender, k ... Intermediate silo, l ... Filling silo, m-1-2 ... Cyclone, X-1 ... 3 ... Anti-blocking Examples of agent addition locations

Claims (6)

In the post-treatment process consisting of granulation process, air transport process and silo storage process of polyolefin production process, including the operation of uniformly attaching the anti-blocking agent to the polyolefin pellet surface, the anti-blocking agent is uniformly attached to the polyolefin pellet surface The operation to be performed is performed by spraying the anti-blocking agent in the polyolefin pellet air-feeding process, and the anti-blocking agent is dried in a pipe at 25 to 60 ° C. to uniformly adhere to the pellet surface, and the operation is performed. A post-treatment method for polyolefin pellets, characterized in that the loss of air feeding pressure of the polyolefin pellets is reduced and biting between the blade of the rotary valve and the casing is prevented. 2. The post-treatment method for polyolefin pellets according to claim 1, wherein the operation for uniformly attaching the antiblocking agent to the surface of the polyolefin pellets is performed at a plurality of locations in the polyolefin pellet emptying step. The operation of uniformly attaching the anti-blocking agent to the polyolefin pellet surface,
Performed by air transport process and granulation process,
The operation in the granulation process ,
The post-treatment method for polyolefin pellets according to claim 1 or 2, wherein an antiblocking agent is added to the circulating water used for watering the polyolefin pellets. The operation of uniformly adhering the anti-blocking agent to the surface of the polyolefin pellets is performed when the polyolefin pellets pass through the rotary valve and while being sent by air.
Or, when the polyolefin pellets are granulated and passed through a rotary valve and while being sent by air,
The post-treatment method for polyolefin pellets according to any one of claims 1 to 3, wherein the concentration of the antiblocking agent on the surface of the polyolefin pellets relative to the weight of the polyolefin pellets is 500 to 10000 wtppm. 5. The polyolefin pellet according to claim 1, wherein the polyolefin pellet is a copolymer resin pellet of a comonomer selected from vinyl acetate, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate and glycidyl methacrylate and ethylene. A post-treatment method for polyolefin pellets according to claim 1. The polyolefin pellet according to any one of claims 1 to 5, wherein the antiblocking agent is any one selected from talc, ethylene-vinyl acetate copolymer, modified polyolefin, or a mixture thereof. Processing method.

Images