JP5074821B2 - Resin pellet blocking evaluation method - Google Patents

Description

  The present invention relates to a method for evaluating blocking of resin pellets used for various moldings.

  Since resin pellets are usually put into a hopper of a molding machine and used for various moldings, they can be put into the hopper and introduced into the molding machine main body through a hopper tank or directly from the hopper of the molding machine. Therefore, the resin product has a granular or long granular shape with a particle diameter of about 1 cm to several mm so that appropriate fluidity can be obtained.

  The package is shipped in tens of kilograms of paper bags (so-called cement bag-like paper bags), for example, 20 kg. In this case, a plurality of bags are stacked, stocked and transported on a pallet. Often done.

  Depending on the type of resin composition that constitutes the resin pellets, especially in the lower bag, a large number of pellets stick to each other (blocking), and the fluidity is lost. This may cause clogging in the hopper and the hopper, which in turn causes a reduction in molding productivity.

  Similarly, in the hopper tank itself, in the resin pellet layer formed inside, the lowermost resin pellet receives all the weight of the resin pellet above it, so that blocking similarly occurs and hopper clogging occurs. .

  Here, when blocking occurs, in the case of relatively weak blocking, it is resolved by applying an impact to the hopper part from the outside, but in the case of strong blocking, such impact is not resolved, The problem cannot be solved without stopping the apparatus and removing the blocked resin pellets, and the problem is particularly great.

  In order to prevent this hopper clogging, various measures have been considered, such as a method using compressed air (Patent Document 1) and a method of supplying with a special feeder attached to the hopper (Patent Documents 2 and 3). However, both are accompanied by hopper modifications.

Here, conventionally, there is no standard for evaluating whether such blocking is difficult to occur, is likely to occur, or can be easily caused (by applying an impact) if it occurs. In the case of a resin that is likely to occur, there was no criterion such as how much the block height could prevent such strong blocking.
JP 11-59785 A JP 2006-143263 A JP 2002-309189 A

  An object of the present invention is to provide a resin pellet blocking evaluation method for evaluating the above-described conventional problems, that is, whether or not blocking has occurred due to the handling of resin pellets, and the influence of blocking.

In order to solve the above problems, the resin pellet blocking evaluation method of the present invention puts a predetermined amount of resin pellets into a bottomed cylindrical container with one end being an open end as described in claim 1, and then And applying a predetermined load from above to the resin pellets in the bottomed cylindrical container while maintaining the bottomed cylindrical container so that the open end is upward and the axis of the cylinder is vertical, Measuring the weight of the resin pellet dropped from the bottomed cylindrical container when the bottomed cylindrical container is held so that the open end is downward and the axis of the cylinder is vertical. It is the blocking evaluation method of the resin pellet to do.

  Moreover, the blocking evaluation method for resin pellets of the present invention is the blocking evaluation method for resin pellets according to claim 1, wherein the amount of the resin pellets falling from the bottomed cylindrical container is as described in claim 2. When the bottomed cylindrical container is not a predetermined amount, the bottomed cylindrical container is predetermined while maintaining the bottomed cylindrical container so that the open end is downward and the axis of the cylinder is inclined at a predetermined angle with respect to the vertical direction. When the impact of the strength is repeatedly applied, the number of times of application of the impact when the resin pellets fall entirely from the bottomed cylindrical container, or the number of times of application of the impact reaches a predetermined value The weight of the resin pellet dropped from the bottomed cylindrical container is measured.

  Moreover, the resin pellet blocking evaluation method according to the present invention is the resin pellet blocking evaluation method according to claim 2, wherein the resin pellet blocking evaluation method according to the present invention is from the bottomed cylindrical container after the predetermined number of impacts are applied. When the falling amount of the resin pellet is not the total amount of the predetermined amount, there is an impact of a predetermined strength while holding the bottomed cylindrical container so that the open end is downward and the axis of the tube is vertical. It is characterized in that it is repeatedly added to the bottom cylindrical container, and the number of times of applying the impact at which the total amount of the resin pellet falls is measured.

  According to the method for evaluating blocking of resin pellets of the present invention, it is possible to very easily evaluate the ease of occurrence of blocking in various resin pellets, the difficulty of occurrence of blocking, and the difficulty of elimination when they occur. In addition, storage conditions in which blocking does not occur can be known in advance. For example, it is possible to know in advance the limit stacking in a paper bag packaging, and it is possible to determine in advance the drying conditions (drying temperature and residence time) that do not cause clogging with respect to residence in a hopper dryer or the like. Since it is possible to know the possibility of problems occurring before production, it is possible to reduce development man-hours and various expenses. Moreover, when there exists a possibility that blocking may arise, an operator can be alerted.

  The bottomed cylindrical container with one end used in the present invention may be made of metal, glass, resin, etc., but preferably has sufficient impact resistance and assumes a hopper. Then, it is preferable that it consists of metal, such as stainless steel, or the thick glass etc. which can understand easily the residual state of the resin pellet inside.

  The shape may be a quadrangular column, a hexagonal column, or the like, but since there are no corners in the cross section, the resin pellets are not fixed to the corners, and thus a cylindrical shape is preferable.

  The bottom of the bottomed cylindrical container may be a flat bottom or may be somewhat rounded. However, since the latter has no corners, the resin fixing block to the corners is not provided in advance. Since it is prevented, it is preferable.

  The amount of the resin pellets to be put into such a bottomed cylindrical container is preferably an amount such that the resin pellet height inside the container is 10 cm or more in consideration of the size of blocking formed, more preferably Is such an amount as to be 5 cm or more.

  Such a predetermined amount of resin pellets is put into a bottomed cylindrical container with one end being an open end, and, for example, the bottomed cylindrical shape is maintained while keeping the open end upward and the axis of the cylinder vertical. A predetermined load can be easily applied to the resin pellets by placing a metal columnar weight or weight having the same diameter as the inner diameter of the container on the resin pellets.

  As the magnitude of the load, for example, assuming that the load received by the resin pellets in the lowermost paper bag when stacked in the form of a paper bag or the load received by the lowermost resin pellet in the hopper tank, Blocking formation can be simulated during actual storage and transportation, or in a resin pellet layer in a hopper tank.

  When the drying hopper is assumed, the time for applying the load may be a time corresponding to the drying time inside the drying hopper (the temperature condition is the same as the drying temperature in the hopper). In addition, when assuming stacked storage, it is preferable to maximize the material quality guarantee period (usually 6 months).

  In the case of long-term storage conditions, multiple experiments were performed while gradually increasing the load application time, and even when the time was further increased, the conditions were such that almost the same results were obtained. Since it can be used as conditions equivalent to long-term storage, the occurrence of blocking during long-term storage can be predicted by examining such conditions through examination.

  Here, in order to better simulate the formation of blocking during actual storage / transportation, it is preferable that the temperature and humidity during actual storage / transportation are examined and the conditions are applied when applying a load. In addition, when drying is performed during supply using a hopper dryer or the like in the actual process, conditions equivalent to the drying conditions (drying temperature, drying time, load conditions received by the lowest resin pellet, etc.) Perform under the same conditions.

  After a predetermined load is applied to the resin pellet from above for a predetermined time, the bottomed cylindrical container is turned over as a first stage of evaluation, with its open end downward and the cylinder axis vertical. The amount of resin pellets falling from the bottomed cylindrical container at this time is measured.

  Here, if no or almost no blocking occurs, the resin pellets fall all, but if blocking occurs, some or all of the resin pellets remain. That is, if all the resin pellets fall from the bottomed cylindrical container, it can be determined that blocking does not occur under the load conditions (and the temperature and the humidity conditions). Furthermore, it can be determined that the smaller the amount of residual resin pellets in the bottomed cylindrical container, the smaller the amount of blocking generated under the load conditions (and the temperature and humidity conditions).

  When the falling amount of the resin pellet from the bottomed cylindrical container is not the total amount, that is, when the resin pellet remains in the bottomed cylindrical container, the process proceeds to the second stage of evaluation. In the second stage, blocking that is relatively easy to eliminate is assumed.

  The bottomed cylindrical container in which the resin pellets remain is maintained so that the open end is downward and the axis of the cylinder is inclined at a predetermined angle with respect to the vertical direction. At this time, a predetermined angle of 30 ° to 45 ° is preferable because it is suitable for evaluation of blocking that is relatively easy to eliminate. A more preferable angle is 40 ° to 50 °.

  Next, impact is repeatedly applied to the bottomed cylindrical container in which the resin pellets remain. As a place where the impact is applied, it is necessary that the impact is transmitted to the whole pellet, and the bottom surface is preferable.

  For impact, it is necessary for relative evaluation that the same thing is applied each time. For example, a hammer (a wooden hammer, a plastic hammer, a rubber hammer, etc.) is fixed to the shaft near the tip of the hammer. It is possible to turn about its axis with the head side of the bottom side down, and hold the bottomed cylindrical container in a position where it comes into contact when the head of this hammer is at the lowest point, By eliminating the holding of the hammer from a position rotated so that the vertical line is at a constant angle, for example, 30 °, a constant impact can be always applied. This method assumes an actual operation of hitting the outside of the hopper relatively lightly with a plastic hammer when the hopper is clogged due to blocking.

  Such impacts are repeatedly applied, and the number of repeated impacts when the resin pellets fall entirely from the bottomed cylindrical container is measured. However, since it is not practical to apply many of the same impacts assuming an actual hopper operation, the resin pellets when the number of such impacts applied is a predetermined number, for example, 30 times or 50 times. Measure the amount of fall.

  If all the resin pellets fall before the number of impacts reaches the specified number of times, it is determined that blocking can be eliminated relatively easily. If the resin pellets remain even after the specified number of times, blocking is difficult to eliminate. Can be determined. The small amount of resin pellets dropped at a predetermined number of times in the latter corresponds to the difficulty in eliminating blocking.

  When the amount of resin pellets falling from the bottomed cylindrical container in the second stage is not the total amount, that is, when the resin pellets remain, the process proceeds to the third stage. The third stage is an evaluation method when blocking is difficult to eliminate.

  The bottomed cylindrical container in which the resin pellets remain is maintained with its open end downward and the axis of the cylinder in the vertical direction. taking measurement. The method of applying the impact may be the same as that in the second stage or may be stronger. This method assumes the actual work of hitting the outside of the hopper comparatively strongly with a plastic hammer when the hopper becomes clogged by blocking with the plastic hopper, even if the outside of the hopper is not cleared even if it is tapped lightly with a plastic hammer. Is.

  Examples of the blocking evaluation method for resin pellets of the present invention will be specifically described below.

<Resin pellets>
The particle shape of the resin pellet used is a cylindrical shape having a diameter of 2.3 mm (average value) and a length of 3.5 mm (average value), and the weight per particle is 0.01 g.

<Bottomed cylindrical container>
As the bottomed cylindrical container with one end being an open end, a test tube-shaped glass container (hereinafter referred to as “cylindrical container”) having an inner diameter of 40 mm, an outer diameter of 42 mm, and a length of 250 mm was used.

<Impact imparting device>
A plastic hammer (commercially available) with a head weight of 400 g was pivotally supported so that the handle (about 20 cm) was on top and the tip of the handle was the axis (Fig. 4 and FIG. 5). The cylindrical container can be fixed so that when the head is at the lowest point, the bottom of the cylindrical container or the side surface in the vicinity thereof contacts. A protractor (not shown) is attached, and the swing-up height of the hammer can be known from the angle from the vertical direction.

<First stage>
The test was performed under three conditions with different loads.
50 g of the above resin pellets (without blocking) were placed in each of the three cylindrical containers a, b and c (see FIG. 1).

  Then, one, two, or three 200 g weights (bottom diameter: 35 mm) were placed on each of these resin pellets (see FIG. 2) and kept at 60 ° C. for 72 hours. These assumed the pellets in the lowermost paper bag when the resin pellets packed in a 20 kg paper bag were stacked in two, three, or four layers and left at 25 ° C. for 4000 hours. Is.

  Thereafter, these cylindrical containers were all turned upside down, their open ends were kept downward, and the cylinder axis was kept vertical (see FIG. 3). As a result, all the resin pellets were dropped in the cylindrical container a, but 3.3 g of the resin pellets were dropped in the cylindrical container b, but the resin pellets in the cylindrical container c were not dropped at all. In addition, when the resin pellet which fell from the cylindrical container a was observed, there was no blocking.

<Second stage>
The second stage evaluation was performed on the resin pellets of the cylindrical containers b and c.
These cylindrical containers are kept so that their open ends are downward and the axis of the cylinder is 60 ° with respect to the vertical direction. With the above-mentioned impact applying device, the swing-up height of the hammer is an angle from the vertical. Was set to 30 °, and impacts were applied 50 times at intervals of about 1 second (see FIG. 4).

  At this time, in the cylindrical container b, the entire amount of the resin pellets was dropped by the 39th impact. At this time, blocking occurred in the dropped resin pellets. On the other hand, in the cylindrical container c, only 3.41 g of resin pellets were dropped by the impact up to 50 times (predetermined number of times), and the rest remained in the cylindrical container c.

<Third stage>
Next, the cylindrical container c in which the resin pellets remained, the open end thereof was kept downward and the axis of the cylinder was kept in the vertical direction, and the impact was repeatedly applied to the cylindrical container c as described above (see FIG. 5). Due to the 12th impact application, the entire amount of the resin pellet dropped. At this time, the dropped resin pellets were blocked.

<Correspondence with actual stacked storage state>
20 kg of the above resin pellets without blocking were packed in paper bags and stacked. In condition A, 2 levels were stacked, in condition B, 3 levels, and in condition C, 5 levels were stacked and stored at 25 ° C. for 6 months.

  Then, when the supply test to the molding machine by a hopper was performed using the lowermost resin pellets, hopper clogging did not occur in the resin pellets in condition A, and hopper clogging occurred in the resin pellets in condition B However, just capping the hopper with a plastic hammer from the outside eliminated the clogging.

  In the resin pellets under condition C, hopper clogging occurred, and the clogging could not be eliminated by just tapping lightly. To eliminate it, the hopper had to be struck strongly.

  From these, in the case of resin pellets that fall entirely in the evaluation in the first stage, hopper clogging does not occur, and in the case of resin pellets that fall in whole quantity in the evaluation in the second stage, hopper clogging occurs, It is relatively easy to eliminate, but in the case of resin pellets that fall in the third stage of evaluation, it can be seen that there is difficulty in supplying with an actual hopper, and blocking with the evaluation method of the present invention is difficult. It was confirmed that the evaluation result of easy occurrence and the actual result corresponded well.

  Furthermore, according to the evaluation method of the present invention, it can be seen that the number of stackable stages where hopper clogging does not occur and the number of possible stages where only hopper clogging is relatively easy can be known in advance. This method can also be applied to the determination of the resin pellet layer thickness in the hopper tank.

It is a model figure which shows the state which put the resin pellet in the bottomed cylindrical container in which one end became the open end in the blocking evaluation method of the resin pellet which concerns on this invention. It is a model figure which shows the state which is applying the load to the resin pellet in a bottomed cylindrical container (cylindrical container). It is a model figure which shows the state (the 1st step of evaluation) which kept the bottom end cylindrical container (cylindrical container) containing the resin pellet that the open end was below and the axis of the cylinder was vertical. It is a model figure which shows the 2nd step of the evaluation method concerning this invention using an impact addition apparatus. It is a model figure which shows the 3rd step of the evaluation method concerning this invention using an impact addition apparatus.

Claims (3)

Put a predetermined amount of resin pellets in a bottomed cylindrical container with one end open,
Next, after applying a predetermined load from above to the resin pellet in the bottomed cylindrical container for a predetermined time while holding the bottomed cylindrical container so that the open end is upward and the axis of the cylinder is vertical ,
Measuring the weight of the resin pellet dropped from the bottomed cylindrical container when the bottomed cylindrical container is held so that the open end is downward and the axis of the cylinder is vertical. Evaluation method for blocking resin pellets.   When the falling amount of the resin pellet from the bottomed cylindrical container is not the total amount of the predetermined amount, the open end is downward and the axis of the cylinder is inclined at a predetermined angle with respect to the vertical direction. The number of times the impact is applied when the resin pellet falls entirely from the bottomed cylindrical container when the bottomed cylindrical container is repeatedly subjected to an impact of a predetermined strength while keeping the bottom cylindrical container. The resin pellet blocking evaluation according to claim 1, wherein the weight of the resin pellet dropped from the bottomed cylindrical container until the number of times the impact is applied reaches a predetermined value is measured. Method.   When the amount of dropping of the resin pellet from the bottomed cylindrical container after the predetermined number of impacts is not the total amount of the predetermined amount, the open end is downward and the axis of the cylinder is vertical. The impact of a predetermined strength is repeatedly applied to the bottomed cylindrical container while keeping the bottomed cylindrical container, and the number of times the impact is applied to which the total amount of the resin pellet falls is measured. Resin pellet blocking evaluation method.

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