JPS589745B2 - Method for manufacturing thermoplastic resin strip aggregate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a thermoplastic resin strip aggregate, and aims to provide a method for continuously manufacturing a lightweight structure with a large porosity by extrusion molding. It is something to do.

Synthetic wood is known as a molded product made by extruding foamed thermoplastic resin through a nozzle with many pores and converging a large number of extruded strips, but each strip is tightly fused together. This results in a molded product with no voids.

On the contrary, the method of the present invention aims to obtain a molded article in which many voids are formed.

This invention was made based on the following basic experimental findings.

That is, a single cap with a depth equal to 30 mm and six types of small holes with diameters ranging from 2.2 mm to 4.2 mm, and conversely a single cap with a diameter equal to 2.2 mm and a depth of 2.2 mm to 4.2 mm. 9
Prepared with 6 types of small holes up to 50mm in diameter.
A mixture of 5 parts of finely powdered talc and 100 parts by weight of polystyrene containing 3 parts of butane gas was attached to a 0 mm extruder and the resin temperature was increased to 10.5 kg for 1 hour.
It was extruded at a temperature of 35-140°C.

As a result, as shown in the table below, when we measured the amount of resin discharged from each small hole, the expansion ratio, diameter, and discharge linear velocity of the foamed strips, we found that there was a larger difference in discharge linear velocity than the expansion ratio and diameter. Therefore, if these foamed strips with different extrusion linear velocities are bundled and molded, the one with the highest extrusion linear velocity is bundled at the same time as the one with the lower extrusion linear velocity while slackening, the extrusion linear velocity is faster. It turned out that it was sliding.

During the extrusion process, the molten resin in the die flows with considerable pressure, and the higher the pressure, the higher the linear velocity of resin discharge from the resin discharge surface of the die.

In addition, the molten resin has a nearly uniform pressure on the resin entry side of the cap, so the linear velocity of resin discharge from the small hole changes depending on the pressure loss when passing through the small hole drilled in the cap. That's why.

The above pressure loss approximately corresponds to Newtonian flow in a circular pipe, and is generally expressed by the following general formula.

In the above equation, P is the pressure difference between both ends of the circular pipe, and μ
is the apparent melt viscosity of the resin, Q is the resin flow rate per unit time,
L is the length of the tube, π is pi, and D is the diameter of the circular tube.

Applying the above general formula to the small hole of the cap used in the present invention, the pressure loss when the molten resin passes through the small hole becomes smaller as the land length of the small hole becomes smaller and the inner diameter becomes larger. I can say that.

Therefore, a resin strip discharged from a small hole with a short land length has a higher resin ejection linear velocity than a resin strip discharged from a small hole with a long land length, and is also discharged from a small hole with a large inner diameter. The resin discharge linear velocity of the resin strip is higher than that of the resin strip discharged from a small hole with a small inner diameter.

The above phenomenon was also confirmed in the case of resin that does not contain a foaming agent, but in the case of non-foamed resin, in order to make a difference in the discharge linear velocity, it is necessary to adjust the amount of discharged resin, that is, the shape of the small hole of the nozzle to the foamed resin. It is necessary to have a larger difference than in the case of .

That is, based on the above knowledge, the present inventor extruded a large number of strips with different linear resin ejection velocities from a single die, and by focusing and fusing the strips, amorphous voids were formed between the strips. The present invention was completed based on the discovery that it is possible to obtain a sliding aggregate having the following shapes.

The present invention is a method for producing a molded article by supplying a thermoplastic resin to an extruder and extruding it as a large number of strips from a die having a large number of small holes, in which the inner diameters or land lengths of the small holes are partially different. Using a cap with many small holes,
By extruding the heated and melted thermoplastic resin into strips from each small hole of the mouthpiece, and taking it off at a drawing speed that is the same as or slower than the advancing speed of the strip that advances the slowest among these strips. , some or all of the strips are guided into the focusing frame while they are still in a molten state, and the strips are fused and integrated at the contact area, and the strips are bonded together. A method for producing a thermoplastic resin strip-shaped aggregate, which comprises obtaining a thermoplastic resin strip-shaped aggregate having irregularly shaped voids and in which the voids account for 20 or more volumes of the whole. This is a summary.

As the thermoplastic resin used in the method of the present invention, most general-purpose thermoplastic resins such as polyolefins such as polyethylene and polypropylene, polyvinyl chloride, polystyrene, and polyamide can be mentioned.

Further, a copolymer or mixed resin of these resins may be used.

Further, as a blowing agent for obtaining a foamed resin aggregate, thermally decomposable solid blowing agents such as azodicarboxylic acid amide and dinitrosopentaethylenetetramine, or butane,
Hydrocarbons that are gaseous at room temperature, such as propane, and easily volatile hydrocarbons, such as pentane and hexane, are used.

The method of the present invention includes feeding the thermoplastic resin to an extruder;
Extruded as a large number of strips from a die with many small holes,
Shape.

At this time, the inner diameters or land lengths of the small holes of the cap are formed to be different, so that the discharge linear velocity of the resin strip discharged from the small holes becomes non-uniform.

If the extruded strip is drawn at the same speed as the strip with the slowest discharge linear velocity, the strip will be straight and the other strips will be curved.

All the strips are bent by drawing at a speed lower than that of the strip with the slowest discharge linear velocity.

As described above, some or all of the resin strips are bent, and the strips are guided into a focusing frame while still in a molten state after extrusion, and are heat-sealed at the contact points of each strip. Ru.

The thermoplastic resin strip aggregate partially fused in this way has irregularly shaped voids between the strips.

It is preferable that the voids be formed by at least 20% of the total volume, and by increasing the number of voids, that is, increasing the porosity, the bulk factor can be increased and an aggregate with excellent strength or cushioning properties can be obtained. .

In addition, in order to obtain a collection of strips with sufficient porosity and large sliding curvature, each small hole is spaced at least twice the inner diameter of the small hole between adjacent small holes. It is desirable that this is provided.

According to the method of the present invention, since there is a difference in resin discharge linear velocity at the time when resin strips are extruded, a strip with a high resin discharge linear velocity inevitably has a higher degree of sliding than a strip with a small resin discharge linear velocity. Therefore, a sliding assembly in which the resin strips are entangled can be obtained without providing a mechanism that gives mechanical vibration to the strips, and the take-up speed can be adjusted to the lowest linear velocity of resin discharge. , i.e. equal to the advancing speed of slow strips,
Alternatively, by adjusting the speed to a slightly faster speed, there is an advantage that a resin strip sliding aggregate having high tensile strength and bending strength including unbent portions can be obtained.

In addition, since the method of the present invention does not require the resin strips to be drawn out vertically, it is also suitable for producing lightweight foamed aggregates with large expanses.

Next, an example of implementation of the method of this invention will be described based on the drawings.

The method of the invention is carried out in the manner shown in FIG.

In FIG. 1, 1 is an extruder, 2 is a die, 3 is a resin discharge plate of the die, 4 is a resin strip, 5 is a guide plate, 6 is a cooling tank, and 7 is a forming roll.

Thermoplastic resin 8 supplied to extruder 1 and made into a molten state
is extruded as resin strips 4 through a number of small holes 11 with different inner diameters and land length intervals bored in the resin discharge plate 3 at the tip of the mouthpiece 2. In this way, the inner diameter, land length, and interval are The resin strips 4 extruded from the small holes 11 with different diameters show various kinds of sliding due to the difference in the resin ejection linear velocity, become entangled, and are fused together at the contact portions of the guide plate 5. It is guided into the cooling tank 6 through the cooling tank 6, and is cooled and solidified while the outside dimensions of the mold are regulated by the forming roll 7 that forms a focusing frame provided in the cooling tank 6. By taking it off, a thermoplastic resin strip aggregate with a high porosity can be obtained.

Note that cooling in the six cooling baths can be performed by spraying cooling liquid, cooling gas, etc., but shower cooling by spraying cooling water from the entire circumference of the assembly near the forming rolls 7 is preferable.

In addition, the position of the guide plate 5 is set at 100 m from the base when trying to freely slide the strips 4 forming the surface of the aggregate.
It is possible to install them at a distance of less than m, but if they are too far apart, the twisted strips will be the only weight and will sag in the vertical direction, causing the aggregate to become distorted if it cools and solidifies. Preferably, it should be installed in close contact with the base.

Furthermore, regarding the shape of the strip-sliding aggregate, when trying to obtain a molded body with a large porosity where the outer dimensions of the aggregate are not strictly required, the frame is simply used to prevent the strips from sagging in the vertical direction. A plate-shaped body like this is sufficient, and if you want to obtain an aggregate that requires relatively high precision in external dimensions, a frame shape that surrounds the entire periphery of the aggregate formed by each strip is used. It is preferable to

In this case, in order to prevent the frame from suppressing the sliding of the strips, it is necessary to use a frame whose inner dimensions are enlarged in a trumpet shape in the direction of travel. It is also possible to forcefully cool the aggregate surface by circulating cooling gas or liquid.

The guide plate can also be provided with a protruding guide on the inner surface of the guide plate to facilitate sliding of the strip.

Next, the shape of the cap in the present invention will be explained based on the drawings.

Figures 2 to 6 show the resin discharge plate 3 of the mouthpiece, and show several examples of the state in which small holes are formed to provide a difference in the linear velocity of resin discharge from the small holes 11. , arrows indicate the direction of resin travel.

The cap shown in FIG. 2 is an example in which the inner diameters of the small holes 11 are different, and the strip 4 discharged from the small hole 11 with a large inner diameter is different from the strip 4 discharged from the small hole 11 with a small inner diameter. Therefore, when these strips 4 are taken at the same time, the strips 4 discharged from the small hole 11 having a large inner diameter are
This means that the degree of sliding increases.

The caps shown in FIGS. 3 and 4 are examples in which the small holes 11 having the same inner diameter are counterbored from the resin discharge end side.

In this case, when the counterbore is made to the same depth from the resin discharge end as shown in Fig. 3, the resin discharge linear velocity increases as the small hole 11 has a larger inner diameter at the resin discharge end, and as shown in Fig. 4. As shown in FIG. 3, when spot facing the same inner diameter from the resin discharge end is performed at different depths, the small hole 11 with a deeper counterbore depth has a higher resin discharge linear velocity.

The cap shown in FIG. 5 is an example in which the land lengths of the small holes 11 are made different. The more ejected the strip 4, the greater the ejected linear velocity.

In the cap shown in FIG. 6, the angle at which the small hole is formed is changed in order to change the land length of the small hole 11.

In other words, the land length of the small hole 11 can be substantially increased by forming the small hole 11 not perpendicularly to the resin discharge surface but at a certain angle.

In order to create a difference in the linear velocity of the resin discharged from the mouthpiece of the resin strip, there is a method of changing the inner diameter of the small hole 11 or the land length as shown in FIGS. 2 to 6. However, the difference in effectiveness between changing the inner diameter and changing the land length is that changing the inner diameter is better than changing the land length, as shown in the general formula above. However, it is preferable to adopt a method of changing the inner diameter because the effect is more clearly seen and the machining of the cap is easier.

In addition, the hole distribution of the small holes 11 of the cap is an essential element for efficiently sliding the resin strip.

That is, in order for the resin strips 4 discharged from the small holes 11 of the cap to slide and become entangled, the strips 4 must be integrated with other strips 4 around each strip 4. It is necessary to have enough space for sliding until the cap is bent, and for this purpose, a hole distribution in which the small holes 11 of the cap are spaced widely is required.

If the distance between the small holes 11 is small, even if the strip 4 discharged from the nozzle is taken at a slower speed than its discharge linear velocity,
Immediately after each strip is ejected from the die, it is thermally fused and integrated with the adjacent strip 4, so the strips 4 do not become entangled, and the resulting molded product is made up of individual strips. This results in not many voids remaining between the rows.

Therefore, among the small holes 11 drilled in the cap 2, the small hole 1 corresponds to the part where the strip 4 discharged from the cap is to be slid.
1 is a hole interval between adjacent small holes 11 that is at least twice the inner diameter, or if there is a difference in inner diameter, at least twice the inner diameter of the small hole 11 with the larger inner diameter among the adjacent small holes 11. It is desirable to have a

Particularly when trying to obtain a foamed strip-shaped aggregate, the resin strips 4 expand rapidly immediately after being discharged from the die, so it is preferable to have a large hole interval.

The shape of the cap used in the method of the present invention can take various shapes depending on the intended use of the aggregate to be obtained. For example, when trying to obtain an assembly that requires a relatively smooth surface quality, a cap 2 having the form shown in FIGS. 7 and 8 is suitable.

FIG. 7 is a front view of the cap 2 seen from the resin discharge side, and FIG. 8 is a sectional view taken along the line A--A of the cap shown in FIG.

In the cap 2 shown in FIGS. 7 and 8, the resin discharge plate 3
Among the many small holes 11 provided in the , the small holes 11 on the outer periphery have a smaller inner diameter than the small holes 11 on the inside, and at the same time, the distance between adjacent small holes 11 is narrow.

When the resin strip 4 is extruded from such a die, the resin strip 4 constituting the inside of the aggregate extruded through the small hole 11 with a large inner diameter constitutes the outer surface of the aggregate that is extruded through the small hole 11 with a small inner diameter. The discharge linear velocity is higher than that of the resin strips, and each strip is discharged with a sufficient distance from the surrounding strips, so that the drawing speed is lower than that of the resin strips forming the outer surface of the aggregate where the discharge linear velocity is slow. By matching the advancing speed of the strips 4 that are discharging, the strips 4 that form the inside of the assembly and that have a faster ejection linear velocity will be able to slide sufficiently because there is sufficient space between them and the surrounding strips 4. They curve and progress as they intertwine with each other.

At this time, the strips 4 that make up the outer surface of the aggregate are ejected at a speed that matches the take-up speed, so they do not slide, and the spacing between the surrounding strips 4 is small, so the strips 4 are ejected. It will be integrated immediately after.

In the molded body thus obtained, the strips 4 on the surface of the aggregate are not bent and there are almost no gaps between the strips 4, while the strips 4 on the inside of the aggregate are not bent. There are voids between the intertwined strips, and the overall result is a sliding aggregate with a smooth surface and a high porosity.

Next, the cap 2 shown in Fig. 9 has partially different degrees of sliding,
This figure shows an example of a die suitable for obtaining a molded article including a dense structural part.

In this nozzle 2, the small holes 11 in the C portion of the resin discharge plate 3 in FIG. 9 have a relatively small inner diameter and are closely spaced with small holes.

On the other hand, the small holes 11 in the D portion have a relatively large inner diameter, and are bored with sufficient space between the holes.

When resin is extruded using such a nozzle 2, the strip 4 discharged from the small hole 11 corresponding to the D portion of the nozzle 2 has a higher resin ejection linear velocity than the strip 4 discharged from the small hole 11 corresponding to the C portion. , since the distance between adjacent strips is large, these strips are taken up at the same time and integrated at a speed slower than the advancing speed of the strip 4 discharged from the small hole 11 of the D portion. The strip discharged from the small hole 11 corresponding to the part has a small degree of sliding, or is formed without sliding,
The strip 4 discharged from the small hole corresponding to the D portion is bent,
The plate-shaped sliding aggregate is formed in an intertwined state, and as a whole, there are parts where there are few voids between the strips in the width direction, and regions where the strips are intertwined and have many voids.

The die in the method of the present invention is intended to obtain a lightweight structure with a large porosity, and for this purpose, the strip discharged from the die requires sufficient space for sliding between adjacent strips. At least the small hole corresponding to the part to be slid is at least twice the inner diameter of the adjacent small hole, and if there is a difference in inner diameter, the small hole with the larger inner diameter of the adjacent small hole is used. It is desirable to provide a hole interval that is at least twice the inner diameter of the hole.

In order to obtain a foamed aggregate with a large spread in %, it is necessary to further increase the hole spacing.

In the method of the present invention, it is possible to obtain a resin strip sliding aggregate even with a non-foamed material, but the difference in ejection linear velocity is more clearly seen when a foamed material is used, and the molded product obtained is also better. It is preferable because it is lightweight.

Figures 10 and 11 show an example of a thermoplastic resin foamed strip sliding aggregate obtained by the method of the present invention. Thin strips 4 are mixed therein, and the thick strips 4 are bent to a large degree.

9 is a fused portion. As described above, the thermoplastic resin strip aggregate obtained by the method of the present invention is made by converging a large number of strips with different degrees of sliding, and fusing and integrating the strips at the contact portions of the strips. Because of this, irregularly shaped voids are formed between the strips, and the bulk factor is large and it is strong, so it can be used for various purposes as a plate, round bar, square bar, etc. as required. I can do it.

For example, it can be used as a drain material for culvert drainage, a core material for various products, etc. In particular, the foamed thin strip sliding aggregate is lightweight, so in addition to the above-mentioned uses, it can also be used as a core material for tatami mats or mats, etc. When polyolefin resin is used for irrigation pipes and other materials, it has good elasticity and can be widely used as a cushioning material.

Next, examples of the method of the present invention will be shown.

Example 1 This example shows a method for obtaining a thermoplastic resin foam strip aggregate having a relatively smooth surface and a large internal porosity.

The cap used in this method had a large number of small holes as shown in FIGS. 7 and 8.

The detailed structure of the cap 2 is as follows.

The resin discharge plate 3 of the mouthpiece is a rectangular plate with a length of 150 m on the long side and 22 mm on the short side, and a thickness of 20 mm in the part that comes into contact with the molten resin.
The one with holes was used.

The distribution of these small holes 11 is as shown in FIGS. 7 and 8.

In Fig. 1, the small holes 11 on the outer periphery have a single inner diameter, and the adjacent small holes 11 have an interval of 4 mm, making a total of 68 holes, and the small holes 11 inside have an inner diameter of 2 mm. The dovetail hole distribution is a total of 32 holes arranged in a staggered manner with an interval of 10 mm in the vertical and horizontal directions, and the land length of each small hole is 2.
It was 0 mm.

In this example, a large number of resin strips 4 were extruded and molded using an apparatus as shown in FIG.

Polystyrene is used as the resin, and polystyrene 10
0 parts by weight and 2 parts by weight of finely powdered talc are uniformly blended, and this mixture is supplied to an extruder. In the extruder, about 3% by weight of butane is compressed to the mixture to form a resin and a blowing agent. were mixed well.

The extruder temperature is 170℃ in the resin supply section and 220℃ in the melting section.
The resin strips 4 are drawn from the cap 2 kept at 140 to 150°C.
Extruded as

In the resin strip 4 extruded in this way, there was a large difference in the ejection linear velocity between the resin strip on the outer periphery of the aggregate and the resin strip on the inside.

In other words, in FIG. 7, the resin strip 4 discharged from the small hole with a small inner diameter has a discharge linear velocity lower than that of the resin discharged from the small hole with a large inner diameter, and the take-up speed is lower than that of the resin discharged from the small hole with a small inner diameter. The resin strip 4 discharged from the small hole with a large inner diameter by making the advancing speed the same as that of the strip 4 is
As the volume increases due to foaming, the resin slides considerably, and at the sliding portion, the contact points fuse with the adjacent resin strips as the assembly progresses, and these aggregates are placed in the cooling tank 6 via the guide plate 5 in FIG. The mixture was passed through a molding roll 7 and cooled and solidified while adjusting the outer dimensions of the aggregate to obtain a thin strip aggregate.

In order to cool the inside of the cooling tank 6, a large number of shower rings were installed in the cooling tank 6, and spray cooling was applied from the entire circumference of the assembly.

The aggregate thus obtained has an external dimension of approximately 130 mm in width,
It is a plate-shaped aggregate with a thickness of about 30 mm, a weight of 200 g/1 mm, and an apparent magnification of about 20 times, and the resin strips 4 forming the plate-shaped surface layer are almost linear in the direction of travel. It is solidified, and the resin strips 4 forming the inside are bent in the vertical and horizontal directions and are solidified in a mutually entangled state, and the resin strips 4 have a porosity of about 50% as a whole. It was a collection of songs.

Example 2 In this example, polypropylene was used as the resin, and the type shown in FIG. 5 was used as the base.

The resin discharge plate 3 of the cap 2 has a diameter of 5 at the part that comes into contact with the molten resin.
0mm circular shape, 1 piece at the center of this circle, 4 pieces on the same circumferential line with a radius of 10 mm from the center, 8 pieces on the same circumferential line with a radius of 15 mm from the center, and 20 mm radius from the center.
A total of 29 small holes 11 with a diameter of 2 mm are drilled on the same circumferential line of the circle, and the land length is determined according to the method shown in Fig. 5. The land length of the small hole 11 located at the center point of the circle is about 10 mm, and the land length of the small hole 11 located on the same circumferential line with a radius of 20 mm from the center is about 10 mm. was approximately 20 mm.

Polypropylene resin was supplied to an extruder and extruded from the above-mentioned die.

The temperature at that time was 200 to 240°C in the extruder and 180 to 200°C at the tip of the die.

The resin strips extruded in this way have a higher ejection linear velocity as they are ejected from small holes with shorter land lengths closer to the center of the circular body. An aggregate was obtained in the same manner as in Example 1, by taking up the strip at a slower speed than the strip that was discharged from the hole and traveling at the slowest speed.

The aggregate obtained in this way is a circular rod-shaped body with a diameter of approximately 30 mm, and each of the strips constituting the aggregate has a greater degree of sliding as it approaches the center of the rod, and there are more gaps between the strips. As a whole, it was an aggregate of resin strips with a porosity of about 20%.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram illustrating the method of the present invention, FIGS. 2 to 6 are sectional views showing the shape of the cap, FIG. 7 is a partially cutaway front view showing the shape of the cap, and FIG. 8 is a cross-sectional view showing the shape of the cap. FIG. 7 is a sectional view taken along line A-A, FIG. 9 is a partially cutaway front view of another base, FIG. 10 is a plan view of the obtained thermoplastic resin striped aggregate, and FIG.
The figure is a sectional view thereof. The main symbols in the drawings are as follows. 1...Extruder, 6...Cooling tank, 2...
・・・Base, 7...Molding roll, 3...
...Resin discharge plate, 9...Fusion part, 4...
-Resin strip, 11...Small hole, 5...Guide plate.

Claims (1)

[Claims] 1. A method for manufacturing a molded article by supplying a thermoplastic resin to an extruder and extruding it as a large number of strips from a die having a large number of small holes, wherein the inner diameter of the small holes or the land length is Using a die in which a large number of small holes with different characteristics are arranged, heated and melted thermoplastic resin is extruded into strips from each small hole of the die, and among these strips, the thin strip with the slowest progressing speed is extruded. Some or all of the strips are bent by drawing at a take-off speed that is equal to or slower than the advancing speed of the strip, and these strips are guided into the focusing frame while still in a molten state, and each The strips are fused and integrated at their contact areas to obtain a thermoplastic resin strip sliding aggregate that has irregularly shaped voids between the strips and in which the voids account for 20% or more by volume of the whole. A method for manufacturing a thermoplastic resin strip-curved aggregate, characterized in that: 2. A method for manufacturing a thermoplastic resin strip sliding aggregate according to claim 1, characterized in that an amorphous void is formed penetrating the strip in the extrusion direction. 3. The thermoplastic resin strip sliding aggregate according to claim 1, characterized in that a cap is used in which a large number of small holes are arranged at intervals of at least twice the inner diameter of the cap. Production method. 4. The method for producing a thermoplastic resin strip sliding aggregate according to claim 1, wherein the thermoplastic resin molded body is a thermoplastic resin foam molded body.