JP2013180536A - Method of cutting strand, and method and device for manufacturing pellet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of cutting a strand, in which a core part is hardly exposed on a cut surface and which can be applied to a plurality of the strands, and a method and device for manufacturing pellets.SOLUTION: A method of cutting a strand includes: a step of positioning a pair of cutting edges which is actuated in a direction crossing the drawing direction of a strand 30 and in which respective edges of first and second cutting edges 10, 20 as a pair of the cutting edges holding and cutting the strand 30 from the opposed directions form an angle α+β and an angle γ+δ of 50° to 110° and form angles α, β, γ, δ of 5° to 55° in both of the upstream direction and the downstream direction of drawing with respect to a surface orthogonal to a strand axis 39, and a distance ε between the edges making a pair when the edges reach the axial center of the strand becomes ≤1/3 of the strand diameter D; and a step of cutting the strand by holding the strand between a pair of the cutting edges.

Description

  The present invention relates to a cutting method having a cross-section in which a core portion is less exposed on a cut surface when a strand made of a synthetic resin consisting of a core portion and a sheath portion or a strand made of a synthetic resin and a synthetic rubber is cut, and The present invention relates to a pellet manufacturing method and manufacturing apparatus using the method.

  When manufacturing synthetic resin molded products, depending on the use, purpose of use, and physical properties of the product, stabilizers, colorants, lubricants, antistatic agents, flame retardants, nucleating agents, foaming agents, It is necessary to mix various additives such as inorganic fillers and synthetic rubber. As a method for producing a molded product made of a synthetic resin in which such various additives, synthetic rubber, etc. are mixed, a method of molding using a compound in which various additives are uniformly dispersed in a synthetic resin in advance, In general, a master batch in which an additive is dispersed at a high concentration is used and kneaded with a synthetic resin during molding.

  As a molding method of synthetic resin molded products, extrusion molding used for molding pipes, electric wires, film sheets, etc., injection molding used for molding parts such as automobiles and home appliances, blow molding used for molding bottles, etc. is there.

  As the synthetic resin used for the production of such a synthetic resin molded product, it is common to use a resin configured in a form called a rice granular pellet. Accordingly, the above-described compounds and master batches are also used in the form of pellets from the viewpoint of stable supply to the molding machine, prevention of classification during mixing, handling, and the like.

  A pelletizer is used to pelletize a resin composition in which various additives are blended with a synthetic resin. A pelletizer is an apparatus that manufactures pellets in combination with an extruder, and includes a die and a cutter. The pellet manufacturing method using the pelletizer can be roughly divided into a cold cut method and a hot cut method.

  The cold cut method is a method in which various additives are melt-kneaded into a synthetic resin using a roll, an extruder, a biaxial kneader, or the like, and then cut in a state solidified by cooling. The cold cut method includes a strand cut method and a sheet cut method, and the strand cut method is common. For example, in this strand cutting method, the resin composition is melt extruded from a die of an extruder into a strand shape, cooled and solidified through a water tank, and then cut into a fixed length with a cutter rotating at high speed to form pellets. Yes.

  The hot cut method is a method in which pellets are obtained by running and cutting a cutter directly on the surface of the die immediately after melt extrusion of the resin composition from a number of nozzles provided on the die of the extruder. It is also called a method. As described above, in the hot cut method, the molten resin composition is cut in air or water, and then solidified by cooling to be pelletized. The hot cut method includes an aerial cut method (narrowly defined hot cut method) that cuts, cools, and solidifies the molten resin composition in the air, an underwater cut method that performs these in water, and a molten resin composition. There is a water ring cut method in which an object is cut in air, and cooling and solidification are performed with a spiral water film formed on the inner wall of the chamber.

  On the other hand, in order to suppress bleed of pellets and antistatic agents, materials that are easy to adhere to each other are used for the core, and materials that are difficult to adhere to each other are pellets that are used for the sheath, or addition that is easy to bleed. Pellets having various two-layer structures have been developed, such as a pellet using a material kneaded in the core and a material not containing the additive in the sheath. When this two-layer pellet is cut with a general pelletizer, it is as follows.

  In the conventional cold cut method, the core portion is exposed on the cut surface of the pellet because it is cut at right angles to the axial direction of the strand. Even in this structure, for example, in the case of covering with an adhesive material, there is no problem unless the core material has a particularly high adhesive property. However, when the material of the core part is a material with particularly strong adhesion, the cut surfaces of the pellets may adhere to each other. In the case of using an additive that easily bleeds, a large amount of additive bleeds from the cut surface, which may cause a problem in long-term storage.

  On the other hand, even when a strand composed of two layers is cut by the hot cut method, the shape is the same as that of the cold cut method immediately after cutting. However, since the material is cut in a molten state, it is cooled and solidified after being cut. At this time, since the material is cooled from the surface, the whole pellet has a round shape. Further, since the sheath portion contracts faster than the core portion, the surface area of the core portion is larger than the surface area of the sheath portion. For this reason, the core part is exposed greatly, and, as in the cold cut method, for example, when the core part material is particularly strong, the core part of the pellets may stick together. It was.

  As a pellet manufacturing method aiming at cutting such a two-layer strand so that the core portion is not exposed, a method as described in Patent Document 1 has been proposed. This method comprises a roll and a rotary cutter, and a strand comprising a core portion and a sheath portion is pressed against the roll with a rotary cutter and punched to produce a pellet.

  Moreover, the method described in Patent Document 2 has a spiral cutting blade and a spiral pressing portion continuous on the upstream side of the cutting blade, and cuts a strand composed of a core portion and a sheath portion, A pellet is produced.

JP-A-55-166216 JP 2004-314516 A

  In the manufacturing method described in Patent Document 1, since the strand is punched with a rotary cutter and a roll, the material of the strand is limited to one having a relatively low hardness. For this reason, it has been difficult to use a strand having a hardness similar to that of a general plastic.

  In addition, the coating on the end face on the roll side tends to be incomplete, and it is difficult to obtain a sufficient effect. On the other hand, although efficient manufacture is usually performed by making a plurality of strands into a plurality of pellets at the same time by cutting once, in the manufacturing method described in Patent Document 2, a pair of strands is used for one strand. A spiral blade is required, and in order to process a plurality of strands at the same time, twice as many strands as the number of strands are required, and the apparatus becomes complicated and expensive. In addition, it is necessary to crush one strand with a pair of spiral blades over a long distance. Like Patent Document 1, the strand material is limited to a low hardness material, or a large material generated by cutting a high hardness material. A structure that can withstand stress was required.

  Accordingly, the present invention has been made to solve the above-described problems. Even when a pellet is produced by cutting a two-layer strand of a core and a sheath, the core is exposed on the cut surface. It is an object of the present invention to provide a strand cutting method, a pellet manufacturing method and an apparatus which are difficult and can be applied simultaneously to a plurality of strands.

The pellet manufacturing method according to the present invention is a method of manufacturing a pellet by cutting a strand extending in the longitudinal direction, which has at least two layers of an inner peripheral side and an outer peripheral side, with respect to the strand take-up direction. A pair of cutting blades that operate in a crossing direction and cut across a strand from opposite directions, with respect to a plane that has an angle of each blade edge of 50 ° to 110 ° and that is orthogonal to the strand axis A pair in which the cutting edge forms an angle of 25 ° or more and 55 ° or less in both the upstream and downstream directions of take-up, and the distance between the pair of cutting edges when the cutting edge reaches the axial center of the strand is 1/3 or less of the strand diameter. The step of positioning the cutting blade and the strand is cut by sandwiching the strand with a pair of cutting blades in a state where the surface hardness of the strand is less than 75 Shore D hardness Preferably and a degree, the planar portion parallel to the direction taking over strands 1/3 or less of the width of the strand diameter is provided on the tip of the cutting blades.

  Preferably, a curved surface having a radius of 1/3 or less of the strand diameter is provided at the tip of the pair of cutting blades.

  Preferably, a flat portion parallel to the take-up direction of the strand is provided at one end of the pair of cutting blades with a width of 1/3 or less of the strand diameter, and a radius of 1/3 or less of the strand diameter is provided at the other end. The curved surface is provided.

  Preferably, when the pair of cutting blades cuts the strand, it operates only in the width direction perpendicular to the longitudinal direction of the strand.

  A pellet production apparatus according to the present invention is an apparatus for producing a pellet by cutting a strand extending in a longitudinal direction, which has at least two layers of an inner peripheral side and an outer peripheral side, with respect to the strand take-up direction. Provided with a pair of cutting blades that operate in the intersecting direction and cut across the strand from the opposite direction, and the angle of each blade edge is not less than 50 ° and not more than 110 °, and with respect to the plane perpendicular to the strand axis Thus, the cutting edge forms an angle of 25 ° to 55 ° in both the upstream and downstream directions of take-up, and the distance between the pair of cutting edges when the cutting edge reaches the axial center of the strand is 1/3 or less of the strand diameter. A pair of cutting blades are positioned, and the strand is cut by sandwiching the strands with the pair of cutting blades in a state where the surface hardness of the strand is less than 75 Shore D hardness.

  The strand cutting method according to the present invention is a method of cutting a strand extending in the longitudinal direction having at least two layers of an inner peripheral side and an outer peripheral side, and operates in a direction crossing the strand take-up direction. In addition, a pair of cutting blades that are cut across the strands from opposite directions, the angle of each blade edge being 50 ° or more and 110 ° or less, and the upstream direction of take-up with respect to the plane perpendicular to the strand axis Positions a pair of cutting blades whose blade edge is 25 ° or more and 55 ° or less in both the downstream direction and the distance between the pair of blade edges when the blade edge reaches the center of the strand axis is 1/3 or less of the strand diameter. And a step of cutting the strand by sandwiching the strand with a pair of cutting blades in a state where the surface hardness of the strand is less than 75 Shore D hardness.

It is sectional drawing which shows the apparatus which cut | disconnects the strand of a two-layer structure based on Embodiment 1 of this invention. It is sectional drawing which shows the apparatus which cut | disconnects the strand of a two-layer structure based on Embodiment 2 of this invention. It is sectional drawing which expands and shows the part enclosed by III in FIG. It is sectional drawing which shows the apparatus which cut | disconnects the strand of a two-layer structure based on Embodiment 3 of this invention. It is an enlarged view of the cutting blade A used in the Example. It is an enlarged view of the cutting blade B used in the Example. It is an enlarged view of the cutting blade C used in the Example. It is an enlarged view of the cutting blade D used in the Example.

  According to the strand cutting method and the pellet manufacturing method according to the present invention, the strand operates in a direction perpendicular to the take-up direction of the strand in a state where the surface hardness of the strand is less than 75 in Shore D hardness, and from the opposite direction. A pair of cutting blades operating with respect to each other, and the angle of the cutting edge is in the range of 50 ° to 110 °, and at the same time from the 25 ° in both the upstream and downstream directions of the take-up with respect to the plane perpendicular to the strand axis A double-layered strand is cut using a cutting blade that is within a range of 55 ° and the distance between the pair of cutting edges when the cutting edge reaches the axial center of the strand is 0 to 1/3 or less of the strand diameter. It is done.

  Moreover, it is desirable to use it as a pair of rotary cutters in which the cutting edge based on the present invention is installed in parallel with the rotation axis and at an equal distance. In that case, a pair of cutting blades contact a single strand with only the length in the width direction of the strand, the stress applied to the cutting blade is small, and the apparatus is also used for cutting a plurality of strands. It can be handled as it is without being complicated.

  The surface hardness of the strand at the time of cutting in the present invention needs to be in a state of less than 75 in Shore D hardness, preferably in a state of less than 70, and more preferably in a state of less than 65. In addition, as a method of adjusting to this state, when cooling through a water tank, for example, it can adjust easily by changing suitably the temperature of a water tank, and the time immersed in a water tank. Further, when it is difficult to adjust the cooling with a water tank in a high melting point material, a method of simply applying cold air to the strand surface may be used.

  In the present invention, the cutting blade has a cutting edge angle of 50 ° to 110 °, preferably 70 ° to 110 °, more preferably 90 ° to 110 °. It is done. If the angle of the blade edge is smaller than 50 °, the end face of the strand cannot be sufficiently covered with the sheath material. On the other hand, when the angle of the blade edge is larger than 110 °, a large force is required for cutting the strands. For example, in simultaneous cutting of a large number of strands, a part that is not partially cut occurs or the apparatus does not last long. Also, the upstream and downstream angles of the take-up with respect to the plane perpendicular to the strand axis are the same angle so that the core portions of both the upstream cut end and the downstream cut end of each pellet are similarly covered with the sheath portion. However, there is no problem even if there is a difference of about 30 °. Further, both the upstream side and the downstream side of the blade edge may be flat or appropriately curved. When the blade edge reaches the center of the strand, the angle between the point in contact with the outer periphery of the strand and the blade edge may be in the above-described range.

  The strand cutting method in the present invention is a cutting method in which the distance between the pair of cutting edges when both the pair of cutting blades reach the axial center of the strand is 1/3 or less of the strand diameter. If the distance is preferably set within a range of less than 1/5 of the diameter of the strand, the wear and damage of the cutting edge can be prevented. Further, there is no problem even if the pair of cutting edges come into contact with each other after cutting.

  In the present invention, a flat portion parallel to the strand having a width of 1/3 or less, more preferably 1/6 to 1/4 of the strand diameter can be provided at the tip of the pair of cutting blades. By installing this portion, it is possible to prevent damage to the blade edge and to effectively improve the coverage of the core portion even in a material with low ductility. At this time, the boundary between the tip of the cutting blade and the upstream and downstream surfaces of the blade is preferably a curved surface having a radius of about 0.1 to 0.5 mm, for example.

  In the present invention, a curved surface portion having a radius of 1/3 or less of the strand diameter, more preferably 1/6 to 1/4 of the strand diameter can be provided at the tip of the pair of cutting blades. By installing this portion, it is possible to prevent damage to the blade edge as in the previous section, and to effectively improve the coverage of the core portion even in a material with low ductility. In addition, the shape of the front-end | tip part of a cutting blade may be the shape which combined both, such as one side being a plane and the other is a curved surface in a pair of cutting blades. Moreover, the material of a cutting blade can be suitably selected according to the physical property and characteristic of a strand constituent material.

  If the method for cutting a strand having a two-layer structure based on the present invention is used, it is possible to almost completely cover the core that could not be achieved by the conventional method, and since the stress applied to the cutting blade is small, Strand processing can also be performed without making the apparatus complex and expensive.

  Moreover, this method is applicable to the part of the cutting blade of the existing pellet manufacturing apparatus, and does not restrict | limit greatly the process before and behind. For example, it can be applied to an apparatus having a process of heating and cooling a strand or performing preliminary crushing, and can effectively produce a two-layer pellet with little core exposure in various apparatuses and materials. .

  Embodiments of the present invention will be described below with reference to the drawings. In the following embodiments, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated. Moreover, it is also possible to combine each embodiment.

(Embodiment 1)
FIG. 1 is a cross-sectional view showing an apparatus for cutting a double-layered strand according to Embodiment 1 of the present invention. Referring to FIG. 1, pellet manufacturing apparatus 1 has first and second blade portions 10 and 20. The first and second blade portions 10 and 20 can move in the directions indicated by arrows 11 and 21. The first and second blade portions 10, 20 have side surfaces 10a, 10b, 20a, 20b and first and second tip portions 12, 22, respectively.

  The strand 30 is located between the first and second blade portions 10 and 20. The strand 30 has a core part 32 located in the center part and a sheath part 31 surrounding the core part 32. Each of the core portion 32 and the sheath portion 31 has a different composition. In this embodiment, the strand 30 has a two-layer structure having a core portion 32 and a sheath portion 31, but the structure of the strand 30 is not only a two-layer structure but also three or more layers. You may use the strand 30 which has a structure. The strand 30 moves in the direction indicated by the arrow 33 and is taken up. The strand 30 has a shape extending in the longitudinal direction along the strand axis 39 as a central axis. In the state shown in FIG. 1, the first and second tip portions 12 and 22 of the first and second blade portions 10 and 20 are bitten into the strand 30.

  The side surface 10a of the first blade portion 10 forms an angle β with respect to the center surface 19 of the blade edge. The side surface 10b of the first blade portion 10 forms an angle α with respect to the center surface 19 of the blade edge. The side surface 20 a of the second blade portion 20 forms an angle δ with respect to the central axis 29. The side surface 20 b of the second blade part 20 forms an angle γ with respect to the central axis 29. These angles satisfy the following relational expression.

25 ° <α <55 °
25 ° <β <55 °
25 ° <γ <55 °
25 ° <δ <55 °
50 ° <α + β <110 °
50 ° <γ + δ <110 °
The distance ε between the first and second tip portions 12 and 22 is preferably 1/3 or less of the diameter of the strand 30.

  The pellet manufacturing method is a method of manufacturing a pellet by cutting a strand 30 extending in the longitudinal direction, which has at least two layers of an inner peripheral side and an outer peripheral side, with respect to the take-up direction of the strand 30 indicated by an arrow 33 The first and second blade portions 10 and 20 as a pair of cutting blades that operate in directions intersecting each other and are cut with the strands 30 sandwiched therebetween from each other have an angle α + β and an angle γ + δ of each blade edge. With respect to a plane that is 50 ° or more and 110 ° or less and that is orthogonal to the strand axis 39, the cutting edge has an angle α, β, γ, or δ that is 25 ° or more and 55 ° or less in both the upstream and downstream directions of the take-up. A step of positioning a pair of cutting blades whose distance ε is equal to or less than 1/3 of the strand diameter D when the cutting edge reaches the center of the axis, and sandwiching the strands with the pair of cutting blades And a step of cutting the strand by. When the pair of cutting blades cuts the strand 30, it operates only in the width direction orthogonal to the longitudinal direction of the strand.

(Embodiment 2)
FIG. 2 is a cross-sectional view showing an apparatus for cutting a double-layered strand according to Embodiment 2 of the present invention. FIG. 3 is an enlarged view of a portion surrounded by III in FIG. Referring to FIGS. 2 and 3, in the pellet manufacturing apparatus according to the second embodiment, the first and second tip portions 12 and 22 are flat, and the width thereof is σ. It differs from the pellet manufacturing apparatus 1 according to. In other words, the first and second tip portions 12 and 22 of the first and second blade portions 10 and 20 as a pair of cutting blades have a width σ equal to or less than 1/3 of the strand diameter D and are parallel to the strand take-up direction. Is provided.

(Embodiment 3)
FIG. 4 is a cross-sectional view showing an apparatus for cutting a double-layered strand according to Embodiment 3 of the present invention. Referring to FIG. 4, in the pellet manufacturing apparatus according to the third embodiment, the first and second tip portions 12 and 22 are curved and the radius thereof is R. Different from the pellet manufacturing apparatus 1. That is, the first and second tip portions 12 and 22 of the first and second blade portions 10 and 20 as a pair of cutting blades are provided with curved surfaces having a radius R equal to or less than 1/3 of the strand diameter D.

  By combining Embodiments 2 and 3, the first tip portion 12 of the first blade portion 10 is provided with a flat portion parallel to the strand take-up direction with a width σ of 1/3 or less of the strand diameter D, A curved surface with a radius R of 1/3 or less of the strand diameter D may be provided at the second tip portion 22 of the two-blade portion 20.

(Example)
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples. The test methods used for measuring the physical properties in these examples and comparative examples are as follows. The raw materials used are shown in Table 1. The cutting blades A to D used are shown in Table 2 and FIGS. Cutting blades A and B are comparative products, and cutting blades C and D are products of the present invention.

  (1) Cross-sectional coverage: Evaluation was based on the ratio of the area where the core portion of the cut surface was covered with the sheath portion. In addition, a cross-sectional coverage can be easily confirmed by coloring a core part and a sheath part suitably.

  (2) Hardness: A plate was prepared by injection molding and measured according to ASTM D-2240 in the same atmosphere as the strand surface temperature (D type, instantaneous value).

  (3) Strand hardness: The surface temperature of the strand at the time of cutting was measured, and (2) hardness at that temperature was defined as the strand hardness.

Example 1
As the double-layered strand, a double-layered strand having a diameter of 3 mm, using 80% by mass of PP shown in Table 1 for the core layer and 20% by mass for the sheath layer, was used. When the two-layer structure strand was cooled so that the surface temperature became room temperature and cut with the cutting blade C shown in Table 2, as shown in Table 3, the core portion was covered with 70% or more of the extended sheath portion. . The Shore D hardness of PP at room temperature is 72.

(Example 2)
As the two-layer structure strand, the same one as in Example 1 was used. When the two-layer structure strand was cooled so that the surface temperature became room temperature and cut with the cutting blade D shown in Table 2, as shown in Table 3, the core portion was covered with 70% or more of the extended sheath portion. . The surface hardness Shore D hardness of PP at room temperature is 72.

(Example 3)
As the two-layer structure strand, the same one as in Example 1 was used. At the time of cutting, the cooling state was adjusted so that the strand surface temperature was 65 ° C., and cutting was performed with the cutting blade C shown in Table 2. As shown in Table 3, 70% or more was covered with the sheath portion with the core portion extended. It was. The Shore D hardness of PP at 65 ° C. is 64.

Example 4
As the two-layer structure strand, the same one as in Example 1 was used. At the time of cutting, the cooling state was adjusted so that the strand surface temperature was 65 ° C. and cut with the cutting blade D shown in Table 2. As shown in Table 3, 90% or more of the core portion was covered with the extended sheath portion. It was. The Shore D hardness of PP at 65 ° C. is 64.

(Example 5)
As the two-layer structure strand, a two-layer strand having a diameter of 3 mm in which 80% by mass of PS shown in Table 1 was used for the core layer and 20% by mass for the sheath layer was used. At the time of cutting, the cooling state was adjusted so that the strand surface temperature was 115 ° C., and when cut with the cutting blade C shown in Table 2, 90% or more was covered with the sheath portion with the core portion extended as shown in Table 3. It was. The Shore D hardness of PS at 115 ° C. was soft and difficult to measure, and was estimated to be 10 or less.

(Example 6)
As the two-layer structure strand, the same strand as in Example 5 was used. At the time of cutting, the cooling state was adjusted so that the strand surface temperature was 115 ° C., and when cut with the cutting blade D shown in Table 2, 90% or more was covered with the sheath portion with the core portion extended as shown in Table 3. It was. The Shore D hardness of PS at 115 ° C. was soft and difficult to measure, and was estimated to be 10 or less.

(Example 7)
As the double-layered strand, a double-layered strand having a diameter of 3 mm in which 80% by mass of PA shown in Table 1 was used for the core layer and 20% by mass for the sheath layer was used. At the time of cutting, the cooling state was adjusted so that the strand surface temperature would be 115 ° C., and the strand was cut with the cutting blade C shown in Table 2. As shown in the table, the core part was covered with 70% or more of the extended sheath part. It was. The Shore D hardness of PA at 115 ° C. is 66.

(Example 8)
As the two-layer structure strand, the same one as in Example 7 was used. At the time of cutting, the cooling state was adjusted so that the strand surface temperature was 115 ° C. and cut with the cutting blade D shown in Table 2. As shown in Table 3, the core part was covered with 70% or more of the extended sheath part. It was. The Shore D hardness of PA at 115 ° C. is 66.

Example 9
As a double-layered strand, a double-layered strand having a diameter of 3 mm, in which 80% by mass of PET shown in Table 1 was used for the core layer and 20% by mass for the sheath layer, was used. At the time of cutting, the cooling state was adjusted so that the strand surface temperature was 100 ° C., and when cut with the cutting blade C shown in Table 2, 70% or more was covered with the sheath portion with the core portion extended as shown in Table 3. It was. The Shore D hardness of PET at 100 ° C. is 68.

(Example 10)
As the two-layer structure strand, the same strand as in Example 9 was used. At the time of cutting, the cooling state was adjusted so that the strand surface temperature was 100 ° C., and when cut with the cutting blade D shown in Table 2, 70% or more was covered with the sheath portion with the core portion extended as shown in Table 3. It was. The Shore D hardness of PET at 100 ° C. is 68.

(Comparative Example 1)
As the two-layer structure strand, the same one as in Example 1 was used. When the two-layer structure strand was cooled so that the surface temperature became room temperature and cut with the cutting blade A shown in Table 2, the core part was exposed and the cross section was not covered as shown in Table 3. The Shore D hardness of PP at room temperature is 72.

(Comparative Example 2)
As the two-layer structure strand, the same one as in Example 1 was used. When the two-layer structure strand was cooled so that the surface temperature became room temperature and cut with the cutting blade B shown in Table 2, the core portion was exposed and the cross section was not covered as shown in Table 3. The Shore D hardness of PP at room temperature is 72.

(Comparative Example 3)
As the two-layer structure strand, a two-layer structure strand having a diameter of 3 mm in which 20% by mass of PP shown in Table 1 was used for the core layer and 80% by mass for the sheath layer was used. When the two-layered strand was cooled to a surface temperature of 65 ° C. and cut with the cutting blade A shown in Table 2, the core was exposed and the cross section was not covered as shown in Table 3. The Shore D hardness of PP at 65 ° C. is 64.

(Comparative Example 4)
As the two-layer structure strand, the same strand as in Comparative Example 3 was used. When the two-layered strand was cooled to a surface temperature of 65 ° C. and cut with a cutting blade B shown in Table 2, the core was exposed and the cross section was not covered as shown in Table 3. The Shore D hardness of PP at 65 ° C. is 64.

(Comparative Example 5)
As the two-layer structure strand, the same strand as in Example 5 was used. When the two-layer structure strand was cooled so that the surface temperature became 115 ° C. and cut with the cutting blade A shown in Table 2, the core was exposed and the cross section was not covered as shown in Table 3. The Shore D hardness of PS at 115 ° C. was soft and difficult to measure, and was estimated to be 10 or less.

(Comparative Example 6)
As the two-layer structure strand, the same one as in Example 7 was used. When the two-layer structure strand was cooled so that the surface temperature became 40 ° C. and cut with the cutting blade C shown in Table 2, the core portion was exposed and the cross section was not covered as shown in Table 3. The Shore D hardness of PA at 40 ° C. is 78.

(Comparative Example 7)
As the two-layer structure strand, the same one as in Example 7 was used. When the two-layer structure strand was cooled so that the surface temperature became 40 ° C. and cut with the cutting blade D shown in Table 2, the core portion was exposed and the cross section was not covered as shown in Table 3. The Shore D hardness of PA at 40 ° C. is 78.

(Comparative Example 8)
As the two-layer structure strand, the same one as in Example 7 was used. When the two-layer structure strand was cooled so that the surface temperature became 115 ° C. and cut with the cutting blade A shown in Table 2, the core was exposed and the cross section was not covered as shown in Table 3. The Shore D hardness of PA at 115 ° C. is 66.

(Comparative Example 9)
As the two-layer structure strand, the same one as in Example 7 was used. When the two-layer structure strand was cooled so that the surface temperature became 115 ° C. and cut with the cutting blade B shown in Table 2, the core portion was exposed and the cross section was not covered as shown in Table 3. The Shore D hardness of PA at 115 ° C. is 66.

(Comparative Example 10)
As the two-layer structure strand, the same strand as in Example 9 was used. When the two-layer structure strand is cooled so that the surface temperature becomes 100 ° C. and cut with the cutting blade A shown in Table 2, as shown in Table 3, the core part is covered with 70% or more of the stretched sheath part. It was. The Shore D hardness of PET at 100 ° C. is 68.

(Comparative Example 11)
As the two-layer structure strand, the same strand as in Example 9 was used. When the two-layer structure strand is cooled so that the surface temperature becomes 100 ° C. and cut with the cutting blade B shown in Table 2, 70% or more is covered with the sheath portion with the core portion extended as shown in Table 3. It was. The Shore D hardness of PET at 100 ° C. is 68.

  DESCRIPTION OF SYMBOLS 1 Pellet manufacturing apparatus, 10 1st blade part, 10a, 10b, 10a, 20b Side surface, 12 1st front-end | tip part, 20 2nd blade part, 22 2nd front-end | tip part, 30 strand, 31 sheath part, 32 core part.

Claims (7)

A method of producing a pellet by cutting a strand extending in a longitudinal direction, having at least two layers of an inner peripheral side and an outer peripheral side,
A pair of cutting blades that operate in a direction intersecting with the strand take-off direction and cut the strand from the opposite direction, the angle of each blade edge being 50 ° to 110 °, and the strand axis The edge of the blade is at an angle of 25 ° to 55 ° in both the upstream and downstream directions of the take-up, and the distance between the pair of blade edges when the blade edge reaches the center of the strand axis is the strand diameter. Positioning the pair of cutting blades to be 1/3 or less;
And a step of cutting the strand by sandwiching the strand with the pair of cutting blades in a state where the surface hardness of the strand is less than 75 Shore D hardness.   The pellet manufacturing method of Claim 1 with which the flat part parallel to the take-off direction of a strand is provided in the front-end | tip of a pair of cutting blade with the width | variety of 1/3 or less of strand diameter.   The pellet manufacturing method according to claim 1, wherein a curved surface having a radius of 1/3 or less of the strand diameter is provided at the tip of the pair of cutting blades.   A flat surface portion having a width of 1/3 or less of the strand diameter and parallel to the strand take-up direction is provided at one end of the pair of cutting blades, and a curved surface having a radius of 1/3 or less of the strand diameter is provided at the other end. The pellet manufacturing method according to claim 1, wherein   The pellet manufacturing method according to any one of claims 1 to 4, wherein when the pair of cutting blades cut the strand, the pellet cutting method operates only in a width direction orthogonal to a longitudinal direction of the strand. An apparatus for producing pellets by cutting a strand extending in the longitudinal direction, having at least two layers of an inner peripheral side and an outer peripheral side,
A pair of cutting blades that operate in a direction intersecting the strand take-off direction and cut the strand from the opposite direction;
The angle of each blade edge is not less than 50 ° and not more than 110 °, and the blade edge has an angle of not less than 25 ° and not more than 55 ° in the upstream and downstream directions of the take-up with respect to the surface orthogonal to the strand axis. When the cutting edge reaches the center, the distance between the pair of cutting edges is 1/3 or less of the strand diameter.
A pellet manufacturing apparatus in which a strand is cut by sandwiching the strand with the pair of cutting blades in a state in which the surface hardness of the strand is less than 75 Shore D hardness. A method of cutting a strand extending in a longitudinal direction, having at least two layers of an inner peripheral side and an outer peripheral side,
A pair of cutting blades that operate in a direction intersecting with the strand take-off direction and cut the strand from the opposite direction, the angle of each blade edge being 50 ° to 110 °, and the strand axis The edge of the blade is at an angle of 25 ° to 55 ° in both the upstream and downstream directions of the take-up, and the distance between the pair of blade edges when the blade edge reaches the center of the strand axis is the strand diameter. Positioning the pair of cutting blades to be 1/3 or less;
And a step of cutting the strand by sandwiching the strand with the pair of cutting blades in a state where the surface hardness of the strand is less than 75 in Shore D hardness.