JP2007297203A - Rotary valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotary valve capable of quantitatively and stably supplying resin pellets with adhesion to air supply pipes and to which less resin is adhered and a method of feeding resin pellets by air by using the rotary valve. <P>SOLUTION: In this rotary valve for quantitatively supplying resin pellets, sandblasting is applied onto the inner surface of a casing and/or rotor blades. A means for cooling the casing is installed on the outer side of the casing of the rotary valve. The amount of resin adhered to the rotary valve is reduced. It is a preferred embodiment that the means for cooling the casing is a jacket for cooling allowing a cooling medium to pass therethrough. The rotary valve is optimally used when the pellets of a copolymer resin formed of a comonomer selected from vinyl polymers acetate, methyl acrylate, ethyl acrylate, butyl acrylate, methyl metacrylate, and glycyzil metaglylate and ethylene. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rotary valve for quantitatively supplying adhesive resin pellets. More specifically, when the adhesive resin pellets are air-fed, a rotary valve for supplying resin pellets that can prevent the resin from adhering to the inner surface of the rotary valve that quantitatively supplies the resin pellets to the air-feeding pipe, and The present invention relates to an air feeding method of resin pellets using the rotary valve.

  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, or the like as an anti-adhesive agent on the pellet surface of an olefin copolymer rubber or polyolefin copolymer (see, for example, Patent Documents 1 and 2). There is a method in which a resin strand is passed through a container filled with a water-dispersed release agent composition, and then pelletized and dried (see Patent Document 3).

  As for the rotary valve, in order to prevent overfilling of the pellets in the rotor pocket when supplying resin pellets, the rotary valve has a bleeder, and a partition plate is provided in the casing with the discharge port of the funnel in between. (See Patent Document 4), the tip of the rotor blade is thinly processed into an edge shape, and contrivances are made to reduce the sandwiching of pellets between the rotor blade and the casing.

  However, with regard to the supply of resin pellets to the air-feeding pipe when air-adhering resin pellets with adhesive properties in particular, problems such as adhesion of resin between the rotor blade and the casing and biting due to retention of the pellets due to adhesion It could not be said that the problem was solved sufficiently, and further improvement was demanded.

(Japanese Patent Laid-Open No. 56-136347, pages 1 to 2) (JP-A-59-124829, pages 1 to 2) (JP-A-9-77890, pages 1 to 3) (Japanese Patent Laid-Open No. 2000-255790, pages 1 to 3)

  In such a situation, the present invention relates to a rotary valve that stably and stably supplies adhesive resin pellets. More specifically, a rotary valve with reduced resin adhesion capable of quantitatively and stably supplying adhesive resin pellets to an air sending pipe, etc., and air feeding of resin pellets using the rotary valve The purpose is to provide a method.

  That is, according to a first aspect of the present invention, there is provided a rotary valve for quantitatively supplying resin pellets, wherein sand blasting is performed on the inner surface of the casing and / or the rotor blade and the casing is cooled outside the casing of the rotor valve. The present invention relates to a rotary valve with reduced resin adhesion. It is a preferred embodiment of the present invention that the means for cooling the casing is a cooling jacket through which a cooling medium passes.

  In the second invention of the present invention, when the pellets of copolymer resin of ethylene and a comonomer selected from vinyl acetate, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate and glycidyl methacrylate are air-fed, The present invention relates to an air feeding method for resin pellets, characterized in that the resin pellets are supplied to an air feeding pipe using the rotary valve of the invention.

  When the Vicat softening point of the copolymer resin is 25 ° C. or less, the effect of the present invention is particularly remarkable.

  According to the present invention, it is possible to provide a rotary valve with reduced resin adhesion for quantitatively and stably supplying adhesive resin pellets to an air feeding pipe and the like, and an air feeding method for resin pellets using the rotary valve. It became possible.

  A copolymer of ethylene and a comonomer selected from vinyl acetate, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, and glycidyl methacrylate has a soft resin and is sticky. In particular, among the above-mentioned copolymers, those having a large amount of comonomer and having a Vicat softening point of 25 ° C. or less have a remarkable tendency. When such resin pellets are air-fed to a storage silo, the resin pellets are quantitatively supplied to the air-feeding pipe, but the resin pellets are caught between the rotor blade and the casing, and the resin pellets are crushed. A phenomenon occurs, a resin film is formed on the inner surface of the rotary valve, and a serious operational failure occurs, such as the rotational load of the rotor rising and the motor tripping. In addition, when the grade of the resin to be manufactured is changed, the attached resin film is peeled off, resulting in a quality problem such as mixing with a different grade of resin.

  The present invention will be described with reference to a schematic diagram (FIG. 1) showing a configuration example of a rotary valve of the present invention. The configuration example of the rotary valve in FIG. 1 includes a bleeder funnel 11 for preventing the overfilling of pellets already proposed, a rotor blade with edge processing, and the like. This is because the present invention can be used to modify the existing rotary valve to exhibit the effect. In the rotary valve of the present invention, the first method for preventing the formation of the resin film on the inner surface of the rotary valve is to prevent the resin from adhering by roughening the inner surface of the casing 13 and / or the tip of the rotor blade 14 by sandblasting or the like. Means. Due to the rough surface processing, the inner surface of the casing and the surface of the rotor blade are roughened, and the adhesive effect is difficult to adhere due to the cooling effect. The rough surface processing is performed so that Rz is 10 to 80 μm, and preferably Rz is about 40 μm ± 10%. If the surface becomes excessively rough, the air in the air feeding pipe will flow backward, making it difficult to quantitatively supply the resin pellets. On the other hand, if the degree of the rough surface is small, resin adhesion cannot be sufficiently prevented. Examples of the rough surface processing performed in the present invention include blast processing such as sand blast processing and shot blast processing, and knurling. Among these, sand blast processing is preferably used.

  Second, it is preferable to provide cooling means such as a cooling jacket outside the casing. The casing is cooled by passing a cooling medium through the cooling jacket. As the cooling medium, water, ethylene glycol, a mixed solution of water and ethylene glycol, or the like is used. For cooling, it is preferable that the inside of the rotary valve is cooled below the Vicat softening point of the resin, and it is particularly preferable that the Vicat softening point can cope with cooling of the resin at 25 ° C. or lower. For this purpose, the temperature of the cooling medium passed through the outer jacket is preferably about 5 ° C. or less.

  As described above, the present invention can be applied to various types of rotary valves. For example, the tip part of the rotor blade is processed into a convex shape, and edge processing is applied to reduce the resin sandwiched between the rotor and the casing so that the convex part is in contact with the casing. By using a bleeder for preventing the pellet from being overfilled in the pellet supply portion, it is effective in preventing the formation of the resin film and the resin biting caused by the resin adhesion.

  The rotary valve of the present invention supplies resin pellets to an air supply pipe when air-coating a copolymer resin of ethylene and a comonomer selected from vinyl acetate, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate and glycidyl methacrylate. It is effective to perform smoothly, and particularly when applied to copolymer pellets having a Vicat softening point of 25 ° C. or less copolymerized with high-concentration vinyl acetate, high-concentration acrylic esters, etc. This prevents the resin contamination in the rotary valve, and is effective without any biting of pellets due to the contamination.

The Vicat softening point is a temperature at which the deformation becomes practically large as the temperature rises and cannot withstand external force. The measurement is performed in accordance with JISK7205-1979, that is, a load of 1 kg is applied through a needle-like indenter having a cross-sectional area of 1 mm ² placed perpendicularly to a test piece in a heating bath and transmitted at a rate of 50 ± 5 ° C./hr. The temperature of the heat transfer medium when the heat medium is raised and the needle-like indenter enters 1 mm is defined as a softening point.

EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and this invention, this invention is not limited to these Examples from the first.
Example 1
Evaluation of the effect of preventing the adhesion of pellets in a rotary valve (hereinafter referred to as RV) was performed using the experimental apparatus shown in FIG. 2 as follows.
The resin used is a pellet of ethylene methyl methacrylate copolymer (EMMA) having a methyl methacrylate concentration of 28 wt%, an MFR of 1000 g / 10 min, and a Vicat softening point of 25 ° C. or less.
The RV has a bleeder for preventing overfilling of resin pellets as shown in FIG. 1. The tip of the rotor blade is subjected to edge processing, and the inside of the casing is sandblasted so that the surface roughness is Rz 40 μm ± 10%. And a cooling jacket provided outside the casing to allow cooling.
Cooling water of about 5 ° C was passed through the cooling jacket so that the inside of the RV casing was adjusted to 25 ° C or lower. Pellets are supplied to the hopper 21, the RV 22 is driven by the motor 23, and the pellets stored in the hopper 21 are discharged to the hopper 25 pressurized by the blower 24. The pellets discharged to the hopper 25 were returned to the hopper 21 through the pipe 26 and circulated for 1 hr. The experimental results are shown in Table 1 as RV-1.

Comparative Example 1
Using the experimental apparatus shown in FIG. 3, the following two types of RV were evaluated as follows for the evaluation of resin adhesion.
RV-2: A standard type rotary valve that does not perform extraction equipment to prevent overfilling of pellets, edge processing of rotor blades, sand blasting inside the casing, and mounting of the casing outer jacket.
RV-3: Rotary valve that performs edge processing of the bleeder and rotor blade to prevent overfilling of pellets on RV-2, and does not perform sand blasting inside the casing and mounting of the casing outer jacket.
For two types of RV-2 and RV-3, pellets are supplied to the hopper 31, the RV 32 is driven by the motor 33, and the pellets stored in the hopper 31 are discharged to the hopper 35 pressurized by the blower 34. . The pellets discharged to the hopper 35 are collected by opening the damper 36 and returned to the hopper 31. This cycle is repeated 30 times. Repeating this operation 30 times is a processing amount equivalent to the 20-minute circulation in Example-1.
The experimental results of Example 1 and Comparative Example-2 are summarized in Table 1. The state of adhesion of the pellets was visually confirmed by the amperage of the RV drive motor and the RV disassembly after the experiment, and it was determined whether there was no adhesion (O) or there was adhesion (X).

  RV-1 used in Example 1 showed no increase in amperage of the driving motor even at the end of the experiment, indicating that there was no dirt due to resin adhesion or biting of resin pellets. After the experiment, the RV was disassembled and the inside was inspected. However, no resin adhered to the inner surface of the RV, and no cleaning was required after the experiment. On the other hand, in RV-2 and RV-3 used in Comparative Example-2, the ampere increased about twice as much at the end of the experiment as compared to the start of the experiment. There was a risk that the motor would trip if the process progressed.

Schematic showing a configuration example of a rotary valve of the present invention Schematic showing the flow of the experimental apparatus used in Example 1 Schematic showing the flow of the experimental apparatus used in Comparative Example 2

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Funnel, 12 ... Hopper, 13 ... Sandblasted casing, 14 ... Rotor blade, 15 ... Rotor, 16 ... Cooling jacket, 17 ... Cooling water, 18 ... Air feed piping, 21 ... Hopper, 22 ... Rotary valve , 23 ... motor, 24 ... blower, 25 ... hopper, 26 ... piping, 31 ... hopper, 32 ... rotary valve, 33 ... motor, 34 ... blower, 35 ... hopper, 36 ... damper

Claims (4)

A rotary valve for quantitatively supplying resin pellets, characterized in that the inner surface of the casing and / or the tip of the rotor blade is roughened and has a means for cooling the casing outside the casing of the rotary valve. Reduced rotary valve. 2. The rotary valve with reduced resin adhesion according to claim 1, wherein the means for cooling the casing is a cooling device for passing a cooling medium. When the pellets of copolymer resin of ethylene and a comonomer selected from vinyl acetate, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate and glycidyl methacrylate are air-fed, using the rotary valve according to claim 1 or 2, A resin pellet air-feeding method comprising supplying resin pellets to an air-feed piping. 4. The resin pellet air feeding method according to claim 3, wherein the copolymer resin has a Vicat softening point of 25 [deg.] C. or less.

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