阅读说明：本技术 粉末压缩物的制造方法 (Method for producing powder compact ) 是由 羽生圭吾 神谷哲 于 2020-03-04 设计创作，主要内容包括：提供能够抑制粉末压缩物的生产效率的降低、且实现硬度提高的粉末压缩物的制造方法。通过用下冲头31和上冲头32压缩供给至臼孔18内的粉末,从而压缩成型为粉末压缩物14。在压缩成型中,进行第1压缩、及该第1压缩之后的第2压缩。在第1压缩中,以第1压缩速度进行压缩,在第2压缩中,以比第1压缩速度慢的第2压缩速度进行压缩。(Provided is a method for producing a powder compact, which can improve hardness while suppressing a decrease in the production efficiency of the powder compact. The powder fed into the mortar hole 18 is compressed by the lower punch 31 and the upper punch 32, thereby compression-molding the powder compact 14. In the compression molding, the 1 st compression and the 2 nd compression after the 1 st compression are performed. In the 1 st compression, the compression is performed at the 1 st compression speed, and in the 2 nd compression, the compression is performed at the 2 nd compression speed which is slower than the 1 st compression speed.)

1. A method for producing a solid compressed powder material obtained by compression molding a powder, comprising:

a 1 st compression step of compressing the powder at a 1 st compression rate; and

and a 2 nd compression step of compressing the powder compact of the powder compressed in the 1 st compression step from a state compressed in the 1 st compression step to a final thickness of the powder compact in a compressed state determined according to a target thickness of the powder compact at a 2 nd compression speed lower than the 1 st compression speed.

2. The method of manufacturing a powder compact according to claim 1, wherein the 1 st compression speed is set to V₁Setting the 2 nd compression speed to V₂Compression velocity ratio V₁/V₂Is 5 or more.

3. The method of producing a powder compact according to claim 1 or 2, wherein in the 2 nd compression step, the combination of the 2 nd compression speed and the compression distance from the state compressed in the 1 st compression step to the final thickness is set so that the rate of change in hardness with respect to the compression distance when the powder compact is compressed is decreased from the state compressed in the 1 st compression step to the state compressed in the powder compact.

Technical Field

The present invention relates to a method for producing a powder compact.

Background

As a powder compact, solid milk obtained by compression molding of milk powder is known (patent document 1). The solid milk is required to have solubility to be rapidly dissolved by being thrown into warm water and to have suitable transportation performance, that is, hardness to prevent damage such as cracking or collapsing during transportation or carrying. In the case of solid milk, the solubility can be improved by increasing the porosity thereof, but the hardness is lowered by increasing the porosity. Therefore, the most suitable porosity is set from the viewpoint of solubility and a property suitable for transportation. The term "porosity" refers to the volume ratio of pores in the bulk volume of the powder.

A rotary tablet press is known as a tablet press for compression molding a powder represented by a powdered milk (for example, see patent document 2). Further, there is known a tablet press machine in which a slide plate having 2 mortar holes is reciprocated in a horizontal direction (see patent document 3). The tablet press machine of patent document 3 has the following configuration: the powder compression molding machine is characterized in that 2 discharge areas are arranged in a mode of separating the molding area, a sliding plate is made to reciprocate between a 1 st position and a 2 nd position, the 1 st position is a position when one mortar hole part is arranged in the molding area and another mortar part is arranged in the other discharge area, the 2 nd position is a position when another mortar hole part is arranged in the molding area and one mortar part is arranged in the other discharge area, a lower punch and an upper punch are respectively made to enter a plurality of mortar holes of the mortar hole part arranged in the molding area to compress and mold powder, and powder compression products obtained by compressing and molding the powder are extruded from the plurality of mortar holes of the mortar hole part arranged in the discharge area.

Documents of the prior art

Patent document

Patent document 1: international publication No. 2006/004190

Patent document 2: japanese laid-open patent publication No. 2000-95674

Patent document 3: japanese laid-open patent publication No. 2007 and 307592

Disclosure of Invention

Problems to be solved by the invention

However, when the same porosity (compression pressure) is maintained for the powder compact, the faster the compression speed, the lower the hardness. Therefore, in order to increase the hardness of the powder compact while maintaining the porosity, it is considered to be useful to suppress the compression rate to be low. However, when the powder is compressed while suppressing the compression rate, there is a problem that the production rate of the powder compressed product is reduced and the production efficiency is deteriorated.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for producing a powder compact, which can improve hardness while suppressing a decrease in production efficiency of the powder compact.

Means for solving the problems

The method for producing a solid compressed powder material obtained by compression molding a powder according to the present invention comprises the steps of: a 1 st compression step of compressing the powder at a 1 st compression rate; and a 2 nd compression step of compressing the powder compact of the powder compressed in the 1 st compression step from the state compressed in the 1 st compression step to a final thickness of the powder compact in a compressed state determined according to a target thickness of the powder compact at a 2 nd compression speed lower than the 1 st compression speed.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, since the 1 st compression by the 1 st compression speed is followed by the 2 nd compression speed which is slower than the 1 st compression speed, the hardness of the powder compact can be increased and the reduction in the production efficiency of the powder compact can be suppressed, as compared with the case where only the 1 st compression speed is followed by the compression.

Drawings

Fig. 1 is an explanatory diagram showing the configuration of a tablet press.

Fig. 2 is an explanatory diagram for explaining the 1 st compression distance of the 1 st compression and the 2 nd compression distance of the 2 nd compression.

Fig. 3 is a graph showing the relationship between the compression speed ratio and the hardness ratio of the powder compact.

Detailed Description

In fig. 1, the tablet press machine 10 of the embodiment is provided with: a molding region 12, and extraction regions 13a and 13b on both sides of the molding region 12. The molding region 12 is a region where the powder is compression-molded into a solid powder compact (hereinafter, simply referred to as a compact) 14. The take-out areas 13a and 13b are areas for taking out the compressed article 14 compression-molded in the molding area 12 to the recovery tray 15. Fig. 1 schematically shows the structure of the tablet press machine 10.

For example, milk powder may be used as the powder, and the solid milk as the compact 14 may be compressed and molded by the tablet press 10. The tablet press 10 and method of compression molding are also useful for making compacts 14 from powders other than powdered milk. The powder is not particularly limited, and examples thereof include: metals, catalysts, inorganic compounds such as surfactants, organic compounds such as sugars, powdered oils and fats, proteins, and mixtures thereof. The compressed product 14 to be produced is not particularly limited, and may be a compressed product of a food, a medicine, an industrial product, or the like.

The tablet press machine 10 is provided with a slide plate 17 slidably in a horizontal direction (left-right direction in the drawing). The slide plate 17 has a 1 st mortar portion 17a on one end side (left side in the drawing) and a 2 nd mortar portion 17b on the other end side (right side in the drawing) in the sliding direction thereof. A plurality of mortar holes 18 penetrating in the thickness direction (vertical direction) of the slide plate 17 are arranged in a matrix form in each of the 1 st mortar portion 17a and the 2 nd mortar portion 17 b.

As shown in the drawing, the slide plate 17 is slid by a slide mechanism (not shown) between a 1 st slide position when the 1 st mortar portion 17a is provided in the molding area 12 and the 2 nd mortar portion 17b is provided in the removal area 13b, and a 2 nd slide position when the 2 nd mortar portion 17b is provided in the molding area 12 and the 1 st mortar portion 17a is provided in the removal area 13 a.

In the molding region 12, a lower punch portion 21 is disposed below the slide plate 17, and an upper punch portion 22 is disposed above. In addition, in the respective take-out areas 13a, 13b, extrusion portions 24a, 24b are disposed above the slide plate 17, respectively. The lower punch head 21 is moved up and down by an actuator 26. The upper punch portion 22 and the extrusion portions 24a and 24b are connected by a connecting member, and are moved up and down integrally by an actuator 27.

A plurality of lower punches 31 stand on the upper portion of the lower punch portion 21, and a plurality of upper punches 32 stand on the lower portion of the upper punch portion 22. The lower punches 31 and the upper punches 32 are arranged in a matrix so as to correspond to the plurality of mortar holes 18 of the mortar, respectively. Thereby, the lower punch 31 and the upper punch 32 are inserted into each mortar hole 18 provided in either the 1 st mortar portion 17a or the 2 nd mortar portion 17b of the molding region 12. As described later, the powder is compression-molded into the compact 14 between the upper end face of the lower punch 31 and the lower end face of the upper punch 32 inserted in the mortar hole 18.

The actuators 26 and 27 are, for example, servo motors driven and controlled by the controller 34, and move the lower punch portion 21 and the upper punch portion 22 up and down. In this example, the speed of the servo motors serving as the actuators 26 and 27 is changed, thereby changing the compression speed at the time of compression molding, that is, the moving speed of the lower punch 31 and the upper punch 32, as described in detail below. The actuators 26 and 27 are not limited to servo motors, and a method of changing the moving speed of the lower punch portion 21 and the upper punch portion 22 is not limited thereto. For example, a hydraulic cylinder or the like may be used. In this example, both the lower punch 31 and the upper punch 32 are moved in the direction of approaching each other during the compression molding, but one may be fixed and only the other may be moved.

A hopper 36 is provided in the tablet press 10 to feed powder to the mortar holes 18. The hopper 36 is disposed so that its bottom surface is close to the upper surface of the slide plate 17. A slit-shaped bottom opening extending in the width direction of the slide plate 17 (the direction perpendicular to the sliding direction) is provided in the bottom surface of the funnel 36. Before compression molding by the lower punch 31 and the upper punch 32, the funnel 36 is reciprocated above a mortar provided in the molding area 12. During this reciprocating movement, powder is supplied from a hopper (not shown) into the hopper 36, whereby a certain amount of powder is supplied into the mortar hole 18 through the bottom opening. In this way, the hopper 36 constitutes a powder supply portion together with the hopper. During compression molding, the funnel 36 moves to a position where it does not interfere with the lowered upper punch portion 22 and the extrusion portions 24a and 24 b. In the case of supplying the powder into the mortar hole 18, the powder is supplied in a state where the lower punch 31 is inserted into the mortar hole 18. In addition, the bottom surface of the hopper 36 can slide with the upper surface of the slide plate 17.

A plurality of extruded bodies 38 are provided below the extruded portions 24a, 24 b. Similarly to the upper punch 32, the extruded bodies 38 of the extruded portions 24a and 24b are arranged in a matrix corresponding to the plurality of mortar holes 18 of the mortar portion. In a state where the slide plate 17 is moved to the 1 st slide position, the extruded body 38 of the extruded portion 24b is inserted into the mortar hole 18 of the 2 nd mortar 17b, and in addition, in a state where the slide plate 17 is moved to the 2 nd slide position, the extruded body 38 of the extruded portion 24a is inserted into the mortar hole 18 of the 1 st mortar 17 a. In this way, the compressed article 14 compression-molded is extruded from the mortar hole 18 by the extrusion body 38 and taken out to the recovery tray 15.

The shape of the compact 14 produced by the tablet press 10 is not particularly limited. Examples of the shape of the compressed article 14 include: a disk shape, a lens shape, a cube shape, a shape in which a concave portion or a convex portion is provided on a surface of a cube, or the like.

The steps of compression molding of the compact 14 based on the above-described tablet press 10 are as follows. The slide plate 17 is moved to, for example, the 1 st slide position. After the slide plate 17 is moved, the actuator 26 is driven to raise the lower punch 21, and the lower punches 31 are inserted into the corresponding mortar holes 18 of the 1 st mortar portion 17a, and stop in a state where the bottoms of the mortar holes 18 are closed. Then, the funnel 36 reciprocates so as to move from one end to the other end (from the right end to the left end in this example) of the 1 st mortar portion 17a and then return to the one end. Further, by supplying the powder to the funnel 36 during this time, a certain amount of powder is supplied into the mortar hole 18 through the bottom opening of the funnel 36.

Subsequently, the upper punch portion 22 and the extrusion portions 24a and 24b are lowered by driving the actuator 27. Thereby, the respective upper punches 32 of the upper punch portion 22 are inserted into the respective mortar holes 18 of the 1 st mortar portion 17a, respectively. Thereafter, the upper punch portion 22 is continuously loweredWhile the undershoot head 21 begins to rise again. Thereby, in each mortar hole 18, the powder is compressed between the upper end surface of the lower punch 31 and the lower end surface of the upper punch 32. When this compression is performed, the compression rate at which the upper end surface of the lower punch 31 and the lower end surface of the upper punch 32 approach each other is changed (switched). I.e. first at the 1 st compression speed V₁Performing a 1 st compression followed by a 2 nd compression speed V₂The 2 nd compression is performed. In the tablet press 10, the 2 nd compression speed V is set₂Specific 1 st compression speed V₁Slow.

The compact 14 can be formed by compressing the powder with the lower punch 31 and the upper punch 32 described above. By releasing the compression by the lower punch 31 and the upper punch 32, the thickness (length in the vertical direction) of the compressed article 14 expands in a state of being compressed. Therefore, in the tablet press machine 10, the distance between the upper end surface of the lower punch 31 and the lower end surface of the upper punch 32 at the end of compression, that is, the final thickness of the compressed object 14 in a state where the compression is maintained, is determined based on the target thickness (hereinafter, referred to as target thickness) of the compressed object 14 as a final formed body in a state where the compression is released, taking into consideration the expansion of the compressed object 14 at the time of releasing the compression.

After the compression is completed, the lower punch portion 21 is lowered, the upper punch portion 22 is raised, and the lower punches 31 and the upper punches 32 are pulled out from the mortar holes 18. At this time, the compressed matter 14 remains in the mortar hole 18.

Next, the slide plate 17 is moved from the 1 st slide position to the 2 nd slide position, and the 2 nd mortar portion 17b is provided in the molding area 12. In the molding region 12, the compressed product 14 is compression molded from the powder in each mortar hole 18 using the 2 nd mortar portion 17b in the same procedure as the compression molding of the powder using the 1 st mortar portion 17a described above.

On the other hand, by moving the slide plate 17 to the 2 nd slide position, the 1 st mortar portion 17a is provided in the removal area 13a together with the compressed matter 14 in the mortar hole 18. Since the extruding portions 24a, 24b are lowered integrally with the upper punch portion 22, the extruding body 38 is inserted into each of the mortar holes 18 of the 1 st mortar portion 17a when the 2 nd mortar portion 17b is compression-molded into the compressed article 14 as described above. Thereby, the compressed matter 14 in each mortar hole 18 of the 1 st mortar portion 17a is extruded onto the recovery tray 15 through the mortar hole 18 by the extruding body 38. The recovery tray 15 moves after the compressed matter 14 is pushed out, and a new recovery tray 15 is set in the take-out area 13 a.

As described above, when the compression molding of the 2 nd mortar portion 17b is used and the removal of the compressed article 14 from the 1 st mortar portion 17a is completed, the slide plate 17 moves to the 1 st slide position. After the movement, the compressed object 14 is extruded from each of the mortar holes 18 of the 2 nd mortar portion 17b provided in the extraction area 13b onto the recovery tray 15 while performing compression molding using the 1 st mortar portion 17a by the same procedure as described above.

Thereafter, similarly, the slide plate 17 is alternately moved to the 1 st slide position and the 2 nd slide position, and compression molding of the powder in the molding region 12 and removal of the compressed material 14 in the removal region 13a or the removal region 13b are performed.

As described above, in the tablet press machine 10, first at the 1 st compression speed V₁After the 1 st compression, at the 2 nd compression speed V₂The 2 nd compression is performed. As shown in fig. 2(a), the compression distance of the 1 st compression and the 2 nd compression is based on the state at the end of the 2 nd compression, that is, at the end of the entire compression stroke in this example. The compression by the lower punch 31 and the upper punch 32 is performed until the punch distance between the upper end surface of the lower punch 31 and the lower end surface of the upper punch 32 becomes the final punch distance L. The final punch spacing L is the final thickness of the compressed object 14 in a state compressed throughout the compression stroke. The final punch distance L is determined by taking into account the expansion of the compressed article 14 when the compression is released as described above, and is smaller than the target thickness of the compressed article 14.

Fig. 2(B) shows a state at the start of the 2 nd compression, that is, at the end of the 1 st compression, and fig. 2(C) shows a state at the start of the 1 st compression. Punch clearance (L + L) from that shown in FIG. 2(C)₁+L₂) To the punch clearance (L + L) shown in FIG. 2(B)₂) The compression until the state of (1) is the 1 st compression. Further, the punch interval (L + L) shown in FIG. 2B₂) The compression from the state of (2) to the state of the final punch interval L shown in fig. 2(a) is the 2 nd compression.

1 st compression distance of 1 st compression is that the punch spacing is reduced in the 1 st compressionDistance L of₁. The 2 nd compression distance of the 2 nd compression is the distance L of the punch spacing reduction in the 2 nd compression₂. Since the 2 nd compression is continued after the 1 st compression without decompressing, the 2 nd compression distance L₂Is a compression distance from a state where the compressed matter 14 is compressed by the 1 st compression to the final thickness (L).

The rate of change of the punch gap in the 1 st compression is the 1 st compression rate V₁The rate of change of the punch gap in the 2 nd compression is the 2 nd compression rate V₂. When the rate of change of the punch gap varies between 1 st compression and 2 nd compression, the average rate is set to the 1 st compression rate V₁2 nd compression speed V₂。

By compressing at a speed V after 1 st compression₁Slow 2 nd compression speed V₂Performing 2 nd compression at a speed V corresponding to the 1 st compression speed₁The same compression speed and the same compression distance (L)₁+L₂) The hardness of the compressed article 14 can be increased as compared with the case of compression. Further, since the 2 nd compression is continued after the 1 st compression, the 2 nd compression distance L can also be shortened₂And is therefore based on a compression speed V at a ratio of 1 st₁Slow 2 nd compression speed V₂The increase in the compression time for performing the 2 nd compression is small. Therefore, the reduction in the manufacturing speed of the compact 14 is slight.

In this example, in order to effectively increase the hardness of the compressed material 14, the 2 nd compression mode, i.e., the 2 nd compression speed V, is determined so as to satisfy the 2 nd compression condition₂And a 2 nd compression distance L₂The 2 nd compression condition is: from a state compressed by the 1 st compression to a state in which the rate of change of the hardness of the compressed matter 14 with respect to the compression distance is reduced when the compressed matter 14 is compressed.

Inventors of the present invention have focused on the compression speed V from 1 st₁1 st compression distance L₁2 nd compression speed V₂2 nd compression distance L₂The compressed products obtained in the above combinations were examined, and as a result, they found: at the 2 nd compression speed V₂Less than the 1 st compression speedDegree V₁When there is a hardness of the compressed object relative to the 2 nd compression distance L₂A specific point (hereinafter referred to as a hardness specific point) at which the rate of change (rate of increase) of the change(s) of (b) decreases. In addition, the inventors have also found that: a 2 nd compression distance L corresponding to the hardness specific point₂According to the 1 st compression speed V₁Is changed and is also subjected to the 2 nd compression speed V₂The influence of (c).

The reason why the hardness peculiar point exists is presumed to be due to a change from a compressed state in which rearrangement of powder particles inside the compact is dominant to a compressed state in which plastic deformation is dominant inside the compact. In addition, the compression speed V is 1 st₁The larger the compression rate V, the larger the energy required for plastic deformation of the inside of the compression product, and therefore the 1 st compression rate V is presumed to be₁And a 2 nd compression distance L corresponding to a hardness specific point₂Is changed and the 2 nd compression distance L₂Is subjected to the 2 nd compression speed V₂The influence of (c).

Based on the above findings, the 2 nd compression is performed so as to satisfy the 2 nd compression condition, whereby the hardness of the compressed article 14 is effectively increased greatly while suppressing an increase in the compression time. The change in the compressed state of the compressed article as described above occurs in the above-described various powders, and when the compressed article is compression-molded from the various powders, it is useful to perform the 2 nd compression so as to satisfy the 2 nd compression condition.

In addition, the 1 st compression speed V is also preferably set₁Relative to the 2 nd compression speed V₂Compression speed ratio (V) ("V₁/V₂) Is set to 5 or more. By setting the compression rate ratio to 5 or more, the hardness of the compressed material 14 can be greatly increased.

The configuration of the tablet press machine 10 is an example, and is not limited as long as the compression can be performed by changing the compression speed in the 1 st compression and the 2 nd compression. In this example, the compression is performed up to the final thickness in the 2 nd compression, but the compression may be performed at a speed changed from the 2 nd compression speed after the 2 nd compression. At this time, the compact 14 is compressed to a final thickness by compression after the 2 nd compression.

Examples

At a 1 st compression speed V₁1 st compression distance L₁2 nd compression speed V₂2 nd compression distance L₂Experiments 1 to 110 in which the compressed articles 14 were compression-molded in various combinations of (a) and (b), the hardness of each of the compressed articles 14 produced in experiments 1 to 110 was evaluated. As the 1 st compression speed V₁1 mm/sec, 10 mm/sec, 100 mm/sec as the 1 st compression distance L₁5mm, 10mm as the 2 nd compression speed V₂The compression distance L is set to 0.25 mm/sec, 1 mm/sec, 2 mm/sec, 10 mm/sec, 50 mm/sec as the 2 nd compression distance L₂And are set to 0.2mm, 0.4mm, 0.8mm and 1.6 mm. Experiments 1-110, except for the 2 nd compression speed V₂Specific 1 st compression speed V₁Examples of slow speeds include, among others, the 1 st compression speed V₁And 2 nd compression speed V₂Same example, 2 nd compression speed V₂Specific 1 st compression speed V₁A fast example. In addition, except for the 1 st compression speed V₁1 st compression distance L₁2 nd compression speed V₂2 nd compression distance L₂Except for the difference, the conditions for producing each compressed product 14 were the same.

Tables 1-1 to 1-3 show the 1 st compression speeds V of experiments 1 to 110₁1 st compression distance L₁2 nd compression speed V₂2 nd compression distance L₂Combinations of (a) and (b).

[ tables 1-1]

[ tables 1-2]

[ tables 1 to 3]

As the powder of the material to be the compact 14, milk powder is used. The milk powder comprises the following components: 11.1g/100g of protein, 57.7g/100g of carbohydrate and 26.1g/100g of lipid. The powdered milk for compression molding is a mixture of powdered milk having a size (particle diameter) of about 5 to 150 μm and a granulated substance of about 100 to 500 μm and a granulated substance of the powdered milk.

Similarly to the tablet press machine 10, the powdered milk is compressed and molded between the lower punch and the upper punch in the mortar hole to produce the compressed product 14. In experiments 1 to 110, 2.0g of milk powder was compressed and molded to obtain a compressed product 14. The shape of the compact 14 was a disk shape having a diameter of 20mm and a thickness (target thickness) of 9.5 mm. The target thickness (9.5mm) was subjected to compression molding with the final punch spacing L (final thickness) set to 8.4 mm.

In addition, as reference experiments R1 to R6, compressed products (hereinafter, referred to as reference compressed products) obtained by compression molding without changing the compression speed in the compression process were produced. Reference will be made to the compression speeds V of experiments R1-R6₀A compression distance L₀Shown in table 2. Other manufacturing conditions of the reference compact are the same as those of the compact 14.

[ Table 2]

In the reference experiments R2, R4, and R6, the compression distance L was measured₀Is 10mm, but the compression distance (punch interval) for compressing the powder (powdered milk) is substantially shorter than the compression distance. In addition, in experiments 1-110, the 1 st compression distance L₁Is 10mm, the compression distance (punch spacing) for which the powder (milk powder) is substantially compressed is also shorter than this compression distance. Therefore, it can be evaluated that the substantial total compression distance in experiments 1-110 is equal to the substantial compression distance in the reference experiments R2, R4, R6.

The hardness of the compacts 14 produced in experiments 1 to 110 was measured, and the hardness and the passing compression speed V of the compacts 14 were measured₀And 1 st compression speed V₁The hardness of the reference compacts obtained by compression molding with the same compression distance as described above was compared. I.e. for the 1 st compression speed V₁Hardness and compression speed V of 1 mm/sec of the compressed article 14 in experiments 1, 2, 5, 6, etc₀The hardness of the reference compacts of reference experiment R2 at 1 mm/s was compared. Similarly, for the 1 st compression speed V₁Hardness and compression speed V of 10 mm/sec of the compressed article 14 in experiments 7, 8, 13, 14 and the like₀The hardness of the reference compacts of reference experiment R4 at 10 mm/s was compared to the 1 st compression speed V₁Hardness and compression speed V of the compression object 14 of experiments 3, 4, 9, 10, etc. at 100 mm/sec₀The hardness of the reference compacts of reference experiment R6 at 100 mm/s was compared.

In the comparison, experiments 1-110 were conducted at the 2 nd compression speed V₂Specific 1 st compression speed V₁The hardness of the compact 14 produced in each experiment of slow compression molding was higher than that of the comparative reference compact. From this, it is found that by compressing the powder at the 1 st compression rate and then further compressing the compressed article 14 compressed in the 1 st compression step to the final thickness of the compressed article 14 at the 2 nd compression rate which is slower than the 1 st compression rate, the hardness of the compressed article 14 is improved, and the hardness of the compressed article 14 can be improved while suppressing an increase in the time required for compression molding.

In addition to the above-described comparison of the hardness, the hardness of the compressed article 14 produced in experiments 1 to 110 was evaluated based on the criterion such as the easy-to-break degree. The evaluation results are shown in the hardness evaluation tables 1-1 to 1-3. The evaluation results obtained by similarly evaluating the hardness of the compacts produced in the reference experiments R1 to R6 are shown in the hardness evaluation column in table 2. The evaluation results (a to D) of the evaluation items are as follows.

A: hard. The defect is not broken even if the film is held by hand and dropped from a height of about 5 cm.

B: and somewhat hard. The allowable hardness of the film will not be broken even if the film is held by hands or transported by a conveyor.

C: somewhat soft. The fracture defect sometimes occurs when the hand is held.

D: and (4) softening. The fracture and defect are easy to occur when the utility model is held by hands.

When the hardness was evaluated in 4 grades as described above, the compression speed V was set₀The hardness of the reference compression produced in the reference experiment R4 was evaluated as "C" at 10 mm/sec, but the 1 st compression speed V corresponding thereto₁10 mm/sec and 2 nd compression speed V₂Specific 1 st compression speed V₁The hardness of the slow compression 14 is rated as "a" or "B" and is higher than the reference compression. In addition, the compression velocity V₀The hardness of the compressed article produced in the reference experiment R6 was evaluated as "D" at a reference experiment R6 of 100 mm/sec, but the 1 st compression speed V corresponding thereto₁Is 100 mm/sec and the 2 nd compression speed V₂Specific 1 st compression speed V₁The hardness of the slow most compact 14 is rated as "a" or "C" and is rated higher than the reference compact. In addition, regardless of the change in the hardness evaluation, as described above, the 2 nd compression speed V was set₂Specific 1 st compression speed V₁The overall compact 14, which was compression molded in a slow manner, had an increased hardness as compared to the comparative reference compact.

Further, the compression rate ratio (═ V) of the compressed product 14 produced in experiments 1 to 110 was examined₁/V₂) The relationship with the hardness ratio. The relationship between the compression rate ratio and the hardness ratio is shown in fig. 3. The hardness ratio is the hardness (H) of the compressed product 14 prepared in experiments 1-110 relative to the compression speed V₀And 1 st compression speed V₁Hardness (H) of reference compressed object with equal and substantially equal compression distance₀) Is (H/H)₀)。

As can be seen from the diagram of fig. 3: when the compression rate ratio is "5" or more, a large hardness ratio, that is, a large increase in hardness can be obtained. Therefore, the 2 nd compression speed V is known₂Specific 1 st compression speed V₁A low compression rate ratio of "5" or more is useful for greatly increasing the hardness of the compressed material 14.

Description of the reference numerals

10 tablet press

14 powder compact

18 mortar hole

31 lower punch

32 upper punch