JP2021112894A - Molding mold and resin molded body manufacturing method - Google Patents

Abstract

To provide a molding mold capable of suppressing occurrence of a poor appearance on a resin molded body when the resin molded body is manufactured.SOLUTION: A molding mold 100 of the present invention is for molding a resin composition 50 into a rod-shaped resin molded body 51. The molding mold 100 comprises: a tubular first member 10; and a tubular second member 20 arranged inside the first member 10 and extending in a longitudinal direction X of the first member 10. The second member 20 is deformable in a radial direction.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing a molding die and a resin molded body.

The rod-shaped resin molded body is used, for example, as a preform for producing a plastic optical fiber (hereinafter, referred to as “POF”) by a melt spinning method. In the melt spinning method, a rod-shaped resin molded body is placed inside the spinning die, and heat is applied to the resin molded body from the spinning die. The heated and softened resin molded body is molded into a fiber shape by passing through a tubular portion at the bottom of a spinning die.

The rod-shaped resin molded product can be produced, for example, by using a tubular molding mold. For example, Patent Document 1 discloses a method of producing a rod-shaped resin molded product by bulk polymerization of a resin raw material in a tubular container.

Japanese Unexamined Patent Publication No. 2012-194310

When a rod-shaped resin molded body is produced by a conventional molding die, the resin molded body tends to have poor appearance such as cracks and sink marks. According to the study of the present inventor, it has been found that when an optical member such as POF is produced from a resin molded product having such poor appearance, particularly cracks, air bubbles are mixed in the optical member.

Therefore, an object of the present invention is to provide a molding die capable of suppressing the occurrence of poor appearance in the resin molded body when manufacturing the resin molded body.

The present invention
A molding die for molding a resin composition into a rod-shaped resin molded body.
The first tubular member and
A tubular second member arranged inside the first member and extending in the longitudinal direction of the first member, and
With
The second member provides a molding die that is deformable in the radial direction.

Furthermore, the present invention
Heat treatment is performed on the resin composition filled inside the second member of the molding mold, and
Cooling the resin composition after the heat treatment and cooling the resin composition so that a rod-shaped resin molded body can be obtained inside the second member.
To provide a method for producing a resin molded product, including the above.

Furthermore, the present invention
A molding die used in a method of molding a resin composition into a rod-shaped resin molded body.
The method comprises cooling the heat treated resin composition to room temperature.
The molding mold is
The first tubular member and
A tubular second member arranged inside the first member and extending in the longitudinal direction of the first member, and
With
The second member provides a molding mold that contains the resin composition and deforms in the radial direction together with the resin composition when the temperature of the heat-treated resin composition drops to room temperature.

According to the present invention, it is possible to provide a molding die capable of suppressing the appearance defect of the resin molded body when manufacturing the resin molded body.

It is an exploded view which shows an example of the molding die of this invention. It is an end view of the 2nd member included in the molding die shown in FIG. It is a figure for demonstrating the state before the 2nd member is deformed in the radial direction. It is a figure for demonstrating the state after the 2nd member is deformed in the radial direction. It is an exploded view which shows another example of the molding die of this invention.

Hereinafter, embodiments of the present invention will be described, but the following description is not intended to limit the present invention to specific embodiments.

(Embodiment 1)
As shown in FIG. 1, the molding die 100 according to the first embodiment includes a first member 10 and a second member 20. The molding die 100 is used for molding the resin composition into a rod-shaped resin molded body. Each of the first member 10 and the second member 20 has a tubular shape. In the present specification, the "cylindrical shape" includes a cylindrical shape, a conical tubular shape, a polygonal tubular shape, and the like, and is preferably cylindrical. The second member 20 is arranged inside the first member 10 and extends in the longitudinal direction X of the first member 10. The longitudinal direction X of the first member 10 is, for example, a direction from one end to the other end of the first member 10, and a direction in which the central axis of the first member 10 extends. The central axis of the first member 10 coincides with, for example, the central axis O of the second member 20.

The second member 20 is not fixed inside the first member 10, and can be deformed in the radial direction, specifically in the direction away from the first member 10. In other words, the second member 20 is deformable in the direction toward the central axis O of the second member 20. The second member 20 can be deformed in the radial direction without breaking. In other words, the second member 20 is reversibly deformable in the radial direction.

The first member 10 has a main body portion 11 for accommodating the second member 20, and may further have flange portions 15 and 16. The shape of the main body 11 is not particularly limited as long as it is cylindrical, but it is preferably cylindrical. The dimensions of the main body 11 are determined according to the dimensions of the resin molded body to be produced, the dimensions of the second member 20, and the like. It is desirable that the main body 11 is hardly deformed when the resin molded product is manufactured.

The flange portion 15 is connected to one end of the main body portion 11 and extends so as to surround the one end. Like the flange portion 15, the flange portion 16 is connected to the other end of the main body portion 11 and extends so as to surround the other end. By attaching a lid (not shown) to each of the flange portions 15 and 16, the inside of the main body portion 11 can be sealed.

The second member 20 may have a main body portion 21 and may further have a slit 25. The main body 21 extends in the longitudinal direction X of the first member 10. As shown in FIG. 2, when observing the end face of the second member 20, the main body 21 has, for example, an arc shape. The central axis O of the second member 20 passes through the center of the virtual circle C defined by the inner peripheral surface of the main body 21, for example.

The slit 25 extends from one end to the other end of the second member 20, for example. The direction in which the slit 25 extends is preferably coincident with the longitudinal direction X of the first member 10, but may deviate from the longitudinal direction X. When the end face of the main body 21 has an arc shape, the slit 25 corresponds to the space between one end and the other end of the arc. The second member 20 preferably has one slit 25, but may have a plurality of slits 25.

The circumferential length L1 of the main body 21 is determined according to the dimensions of the resin molded product to be produced, and is, for example, 50 mm to 1500 mm, preferably 100 mm to 800 mm. The width L2 of the slit 25 is, for example, 1 mm to 80 mm, preferably 2 mm to 30 mm. The width L2 of the slit 25 means the distance between a pair of end faces of the slit 25 in the direction in which the slit 25 extends, for example, the direction orthogonal to the longitudinal direction X of the first member 10. When the end face of the main body 21 has an arc shape, the width L2 of the slit 25 corresponds to the distance between one end and the other end of the arc.

In the second member 20, the ratio of the width L2 of the slit 25 to the length L1 in the circumferential direction of the main body 21 is not particularly limited, and is, for example, 0.001 to 0.1, preferably 0.005 to 0. It is 05.

The circumference of the virtual circle C defined by the inner peripheral surface of the main body 21 is determined according to the dimensions of the resin molded product to be produced, and is, for example, 60 mm to 1500 mm. The diameter of the virtual circle C is also determined according to the dimensions of the resin molded product to be produced, and is, for example, 20 mm to 500 mm. As will be described later, when the second member 20 is formed by bending the sheet, the value obtained by adding the thickness of the sheet to the diameter of the virtual circle C corresponds to the diameter of curvature of the sheet.

The thickness of the main body 21 is not particularly limited as long as the radial deformation of the second member 20 is not hindered, and is, for example, 2.0 mm or less, preferably 1.0 mm or less, and more preferably 0. It is 5.5 mm or less. The lower limit of the thickness of the main body 21 is not particularly limited, and is, for example, 0.01 mm. The length of the main body 21 in the longitudinal direction is determined according to the dimensions of the resin molded product to be produced, and is, for example, 100 mm to 800 mm.

The first member 10 (particularly the main body 11) includes, for example, a metal material. Examples of the metal material contained in the first member 10 include Hastelloy. The first member 10 may contain a metal material as a main component, or may be substantially made of a metal material. The "main component" means a component contained most in the first member 10 in terms of weight ratio. The first member 10 may contain impurities in addition to the metal material.

The material of the second member 20 (main body 21) is not particularly limited as long as the radial deformation of the second member 20 is not hindered. The second member 20 includes, for example, at least one selected from the group consisting of a heat-resistant resin and a metal material, and preferably contains a heat-resistant resin. Examples of the heat-resistant resin include a fluororesin, a polyimide resin, a polyamide resin, a polyether ether ketone resin, a polyetherimide resin, and a polyphenylene sulfide resin, and a fluororesin is preferable. Examples of the fluororesin include polytetrafluoroethylene (PTFE) and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and PTFE is preferable. Examples of the metal material include aluminum, nickel and Hastelloy, and aluminum is preferable.

The content of the heat-resistant resin or metal material in the second member 20 is, for example, 50 wt% or more, preferably 80 wt% or more, and more preferably 90 wt% or more. The second member 20 may be substantially made of a heat-resistant resin or a metal material.

The second member 20 is made of, for example, a bendable sheet. In other words, the second member 20 is formed by bending the sheet. Specifically, the curved sheet itself corresponds to the main body 21 of the second member 20, and in the curved sheet, the space between one end and the other end facing each other corresponds to the slit 25. In the present specification, "curvable" means that the bending fracture strain (bending strain when the sheet breaks) of the sheet constituting the second member 20 is 0.05 or more, preferably 0.1 or more. Means. The bending fracture strain of the sheet constituting the second member 20 can be measured, for example, by a method in accordance with the provisions of Japanese Industrial Standards (JIS) K7171: 2016.

The longitudinal elastic modulus (Young's modulus) of the sheet constituting the second member 20 is, for example, 200,000 MPa or less, preferably 100,000 MPa or less, more preferably 50,000 MPa or less, still more preferably 5,000 MPa or less, and particularly preferably. Is 1000 MPa or less. The lower limit of the Young's modulus of the sheet is not particularly limited, and is, for example, 50 MPa. The Young's modulus of the sheet can be specified, for example, by a method according to the provisions of JIS K7161-1: 2014.

Next, a method of manufacturing a resin molded body using the molding die 100 will be described. The method for producing the resin molded body of the present embodiment is to heat-treat the resin composition filled inside the second member 20 of the molding die 100, and to form a rod-shaped resin molded body inside the second member 20. Including cooling the resin composition after the heat treatment so as to be obtained.

In the present embodiment, the resin composition contains, for example, a fluorine-containing polymer (polymer (P)). The polymer (P) preferably contains substantially no hydrogen atom from the viewpoint of suppressing light absorption due to the expansion and contraction energy of the CH bond, and all hydrogen atoms bonded to the carbon atom are fluorine atoms. It is particularly preferable that it is replaced with. In the present specification, the fact that the polymer (P) does not substantially contain hydrogen atoms means that the content of hydrogen atoms in the polymer (P) is 1 mol% or less.

The polymer (P) preferably has a fluorine-containing aliphatic ring structure. The fluorine-containing aliphatic ring structure may be contained in the main chain of the polymer (P) or in the side chain of the polymer (P). The polymer (P) has, for example, a structural unit (A) represented by the following formula (1).

In the formula (1), R _ff ^{1 to} R _ff ⁴ independently represent a fluorine atom, a perfluoroalkyl group having 1 to 7 carbon atoms, or a perfluoroalkyl ether group having 1 to 7 carbon atoms. R _ff ¹ and R _ff ² may be connected to form a ring. "Perfluoro" means that all hydrogen atoms bonded to carbon atoms are replaced by fluorine atoms. In the formula (1), the number of carbon atoms of the perfluoroalkyl group is preferably 1 to 5, more preferably 1 to 3, and even more preferably 1. The perfluoroalkyl group may be linear or branched. Examples of the perfluoroalkyl group include a trifluoromethyl group, a pentafluoroethyl group, a heptafluoropropyl group and the like.

In the formula (1), the number of carbon atoms of the perfluoroalkyl ether group is preferably 1 to 5, and more preferably 1 to 3. The perfluoroalkyl ether group may be linear or branched. Examples of the perfluoroalkyl ether group include a perfluoromethoxymethyl group.

When R _ff ¹ and R _ff ² are connected to form a ring, the ring may be a 5-membered ring or a 6-membered ring. Examples of this ring include a perfluorotetrahydrofuran ring, a perfluorocyclopentane ring, and a perfluorocyclohexane ring.

Specific examples of the structural unit (A) include the structural units represented by the following formulas (A1) to (A8).

The structural unit (A) is preferably the structural unit (A2) among the structural units represented by the above formulas (A1) to (A8), that is, the structural unit represented by the following formula (2).

The polymer (P) may contain one or more structural units (A). In the polymer (P), the content of the structural unit (A) is preferably 20 mol% or more, more preferably 40 mol% or more, based on the total of all the structural units. The polymer (P) tends to have higher heat resistance when the structural unit (A) is contained in an amount of 20 mol% or more. When the structural unit (A) is contained in an amount of 40 mol% or more, the polymer (P) tends to have higher transparency and higher mechanical strength in addition to high heat resistance. In the polymer (P), the content of the structural unit (A) is preferably 95 mol% or less, more preferably 70 mol% or less, based on the total of all the structural units.

The structural unit (A) is derived from, for example, a compound represented by the following formula (3). In equation (3), R _ff ^{1 to} R _ff ⁴ are the same as in equation (1). The compound represented by the formula (3) can be obtained by a production method already known, for example, the production method disclosed in JP-A-2007-504125.

Specific examples of the compound represented by the above formula (3) include compounds represented by the following formulas (M1) to (M8).

The polymer (P) may further contain other structural units in addition to the structural unit (A). Examples of other structural units include the following structural units (B) to (D).

The structural unit (B) is represented by the following formula (4).

In the formula (4), R ^{1 to} R ³ independently represent a fluorine atom or a perfluoroalkyl group having 1 to 7 carbon atoms. R ⁴ represents a perfluoroalkyl group having 1 to 7 carbon atoms. The perfluoroalkyl group may have a ring structure. A part of the fluorine atom may be replaced with a halogen atom other than the fluorine atom. A part of the fluorine atom in the perfluoroalkyl group may be substituted with a halogen atom other than the fluorine atom.

The polymer (P) may contain one or more structural units (B). In the polymer (P), the content of the structural unit (B) is preferably 5 to 10 mol% with respect to the total of all the structural units. The content of the structural unit (B) may be 9 mol% or less, or 8 mol% or less.

The structural unit (B) is derived from, for example, a compound represented by the following formula (5). In equation (5), R ^{1 to} R ⁴ are the same as in equation (4). The compound represented by the formula (5) is a fluorine-containing vinyl ether such as perfluorovinyl ether.

The structural unit (C) is represented by the following formula (6).

In formula (6), R ^{5 to} R ⁸ independently represent a fluorine atom or a perfluoroalkyl group having 1 to 7 carbon atoms. The perfluoroalkyl group may have a ring structure. A part of the fluorine atom may be replaced with a halogen atom other than the fluorine atom. A part of the fluorine atom in the perfluoroalkyl group may be substituted with a halogen atom other than the fluorine atom.

The polymer (P) may contain one or more structural units (C). In the polymer (P), the content of the structural unit (C) is preferably 5 to 10 mol% with respect to the total of all the structural units. The content of the structural unit (C) may be 9 mol% or less, or 8 mol% or less.

The structural unit (C) is derived from, for example, a compound represented by the following formula (7). In formula (7), R ^{5 to} R ⁸ are the same as in formula (6). The compound represented by the formula (7) is a fluorine-containing olefin such as tetrafluoroethylene and chlorotrifluoroethylene.

The structural unit (D) is represented by the following formula (8).

In formula (8), Z represents an oxygen atom, a single bond, or -OC (R ¹⁹ R ²⁰ ) O-, and R ^{9 to} R ²⁰ are independently fluorine atoms and perfluoro having 1 to 5 carbon atoms. Represents an alkyl group or a perfluoroalkoxy group having 1 to 5 carbon atoms. A part of the fluorine atom may be replaced with a halogen atom other than the fluorine atom. A part of the fluorine atom in the perfluoroalkyl group may be substituted with a halogen atom other than the fluorine atom. A part of the fluorine atom in the perfluoroalkoxy group may be substituted with a halogen atom other than the fluorine atom. s and t independently represent integers 0 to 5 and s + t 1 to 6 (where Z is −OC (R ¹⁹ R ²⁰ ) O−, s + t may be 0).

The structural unit (D) is preferably represented by the following formula (9). The structural unit represented by the following formula (9) is a case where Z is an oxygen atom, s is 0, and t is 2 in the above formula (8).

In formula (9), R ¹⁴¹ , R ¹⁴² , R ¹⁵¹ , and R ¹⁵² each independently represent a fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a perfluoroalkoxy group having 1 to 5 carbon atoms. .. A part of the fluorine atom may be replaced with a halogen atom other than the fluorine atom. A part of the fluorine atom in the perfluoroalkyl group may be substituted with a halogen atom other than the fluorine atom. A part of the fluorine atom in the perfluoroalkoxy group may be substituted with a halogen atom other than the fluorine atom.

The polymer (P) may contain one or more structural units (D). In the polymer (P), the content of the structural unit (D) is preferably 30 to 67 mol% with respect to the total of all the structural units. The content of the structural unit (D) is, for example, 35 mol% or more, 60 mol% or less, or 55 mol% or less.

The structural unit (D) is derived from, for example, a compound represented by the following formula (10). In formula (10), Z, R ^{9 to} R ¹⁸ , s and t are the same as in formula (8). The compound represented by the formula (10) is a fluorine-containing compound having two or more polymerizable double bonds and capable of cyclization polymerization.

The structural unit (D) is preferably derived from the compound represented by the following formula (11). In equation (11), R ¹⁴¹ , R ¹⁴² , R ¹⁵¹ , and R ¹⁵² are the same as in equation (9).

Specific examples of the compound represented by the formula (10) or the formula (11) include the following compounds.
CF ₂ = CFOCF ₂ CF = CF ₂
CF ₂ = CFOCF (CF ₃ ) CF = CF ₂
CF ₂ = CFOCF ₂ CF ₂ CF = CF ₂
CF ₂ = CFOCF ₂ CF (CF ₃ ) CF = CF ₂
CF ₂ = CFOCF (CF ₃ ) CF ₂ CF = CF ₂
CF ₂ = CFOCFClCF ₂ CF = CF ₂
CF ₂ = CFOCCl ₂ CF ₂ CF = CF ₂
CF ₂ = CFOCF ₂ OCF = CF ₂
CF ₂ = CFOC (CF ₃ ) ₂ OCF = CF ₂
CF ₂ = CFOCF ₂ CF (OCF ₃ ) CF = CF ₂
CF ₂ = CFCF ₂ CF = CF ₂
CF ₂ = CFCF ₂ CF ₂ CF = CF ₂
CF ₂ = CFCF ₂ OCF ₂ CF = CF ₂
CF ₂ = _{CFOCF 2} CFClCF = CF ₂
CF ₂ = CFOCF ₂ CF ₂ CCl = CF ₂
CF ₂ = _{CFOCF 2} CF ₂ CF = CFCl
CF ₂ = CFOCF ₂ CF (CF ₃ ) CCl = CF ₂
CF ₂ = CFOCF ₂ OCF = CF ₂
CF ₂ = CFOCCl ₂ OCF = CF ₂
CF ₂ = CClOCF ₂ OCCl = CF ₂

The polymer (P) may further contain other structural units other than the structural units (A) to (D), but substantially includes other structural units other than the structural units (A) to (D). It is preferable not to include it. It should be noted that the fact that the polymer (P) does not substantially contain other structural units other than the structural units (A) to (D) means that the structural unit (A) is relative to the total of all the structural units in the polymer (P). ) To (D) means that the total is 95 mol% or more, preferably 98 mol% or more.

The polymerization method of the polymer (P) is not particularly limited, and for example, a general polymerization method such as radical polymerization can be used. The polymerization initiator for polymerizing the polymer (P) may be a fully fluorinated compound. In the production method of the present embodiment, the polymer (P) may be polymerized inside the molding die 100. That is, in the production method of the present embodiment, the resin composition containing the polymer (P) is obtained by polymerizing the monomer group containing the compound represented by the formula (3) inside the second member 20. It may further include gaining.

The glass transition temperature (Tg) of the polymer (P) is not particularly limited, and may be, for example, 100 ° C. to 140 ° C., 105 ° C. or higher, or 120 ° C. or higher. As used herein, Tg means the midpoint glass transition temperature (T _mg ) determined in accordance with JIS K7121: 1987.

The resin composition may contain the polymer (P) as a main component, and is preferably composed substantially only of the polymer (P). The resin composition may further contain additives such as a refractive index adjuster. The resin composition is, for example, a solid at room temperature (25 ° C.). The shape of the resin composition is not particularly limited, and is, for example, powdery.

In the production method of the present embodiment, the resin composition is softened by performing a heat treatment on the resin composition. The resin composition may be melted by heat treatment. The shape of the resin composition after the heat treatment is, for example, a liquid or a paste. The temperature of the heat treatment is, for example, 120 ° C. to 350 ° C., preferably 150 ° C. to 300 ° C. The heat treatment time is not particularly limited, and is, for example, 2 hours to 100 hours. The heat treatment of the resin composition can be performed, for example, by using a heater (not shown) installed outside the first member 10.

The heat treatment may be performed in a reduced pressure atmosphere or a vacuum atmosphere. The heat treatment may be performed in an atmosphere containing an inert gas such as nitrogen gas or argon gas.

The method for cooling the resin composition is not particularly limited. For example, the resin composition may be cooled by dissipating heat from the resin composition. The cooling treatment is performed, for example, until the temperature of the resin composition reaches room temperature. The cooling treatment may be performed in the same atmosphere as the heat treatment.

By cooling the resin composition, the resin composition is solidified to obtain a rod-shaped resin molded product. The specific shape of the resin molded body is determined according to the shape of the second member 20, and examples thereof include a columnar shape, a truncated cone shape, and a polygonal columnar shape.

In the manufacturing method of the present embodiment, when the resin composition is cooled, the second member 20 is deformed in the radial direction. In other words, the second member 20 deforms in the radial direction when the temperature of the heat-treated resin composition decreases (for example, decreases to room temperature). Hereinafter, the radial deformation of the second member 20 will be described with reference to FIGS. 3 and 4.

FIG. 3A is a schematic perspective view showing the resin composition 50 and the second member 20 before the resin composition 50 is cooled, that is, immediately after the heat treatment is performed. In FIG. 3A, the first member 10 is omitted. FIG. 3B is a cross-sectional view of the molding die 100 before cooling the resin composition 50. In FIG. 3B, the outer peripheral surface of the main body 21 of the second member 20 is in contact with the main body 11 of the first member 10. However, the outer peripheral surface of the main body 21 does not have to be in contact with the main body 11.

FIG. 4A is a schematic perspective view showing the resin molded body 51 and the second member 20 obtained by cooling the resin composition 50. Similar to FIG. 3A, the first member 10 is omitted in FIG. 4A. As shown in FIG. 4A, a rod-shaped resin molded body 51 is formed inside the second member 20. FIG. 4B is a cross-sectional view of the molding die 100 containing the resin molded body 51.

When the resin composition 50 is cooled, the resin composition 50 shrinks in the radial direction while gradually solidifying as its temperature decreases. At this time, the resin composition 50 is attached to the main body 21 of the second member 20. Therefore, the main body 21 of the second member 20 is deformed so as to follow the shrinkage of the resin composition 50. In other words, the second member 20 deforms in the radial direction together with the resin composition 50 when the temperature of the heat-treated resin composition 50 decreases. Specifically, as the resin composition 50 shrinks, the width of the slit 25 of the second member 20 decreases. That is, the width of the slit 25 of the second member 20 shown in FIGS. 4 (a) and 4 (b) is smaller than the width of the slit 25 shown in FIGS. 3 (a) and 3 (b). At the stage when the resin molded body 51 is formed, the second member 20 does not have to have the slit 25. As the width of the slit 25 is reduced in this way, the second member 20 is deformed in the radial direction.

As can be seen from FIGS. 3 and 4, the second member 20 is deformed in the direction away from the first member 10, that is, in the direction toward the central axis O of the second member 20, as the resin composition shrinks. As a result, a space is created between the main body 21 of the second member 20 and the main body 11 of the first member 10, or the volume of the space between the main body 21 and the main body 11 increases. In other words, the second member 20 is deformed so that the area of the virtual circle C defined by the inner peripheral surface of the main body 21 is reduced.

When the second member 20 is deformed in the radial direction due to the shrinkage of the resin composition, stress is generated in the second member 20. This stress is not particularly limited, and is, for example, 5.0 × 10 ^-3 MPa or less, preferably 1.0 × 10 ^-3 MPa or less, and more preferably 5.0 × 10 ^-4 MPa or less. It is more preferably 1.0 × 10 ^-4 MPa or less, and particularly preferably 5.0 × 10 ^-5 MPa or less. The smaller the stress generated in the second member 20, the more easily the second member 20 is deformed in the radial direction.

The stress σ generated in the second member 20 due to the deformation of the second member 20 in the radial direction can be calculated by the following equations (I) to (III).

In the formula (I), P is the load (N) required to deform the second member 20 in the radial direction, and A is the cross-sectional area (mm ² ) of the main body 21 of the second member 20. .. The cross-sectional area A of the main body 21 is obtained by the product of the length b (mm) of the main body 21 in the longitudinal direction and the thickness h (mm) of the main body 21.

In the formula (II), δ is the amount of deflection (mm) generated in the main body 21 due to the radial deformation of the second member 20. R is the radius of curvature (mm) of the main body 21 after the second member 20 is deformed in the radial direction. The radius of curvature R of the main body 21 is the value obtained by adding the thickness h of the main body 21 to the diameter of the virtual circle C defined by the inner peripheral surface of the main body 21 (curvature diameter of the main body 21) divided by 2. Corresponds to the value. α is a value (radian) obtained by dividing the central angle 2α (see FIG. 2) in the virtual circle C, which is represented by the central axis O and the slit 25, by 2. In addition, α is a value after the second member 20 is deformed in the radial direction.

In formula (III), b is the length (mm) of the main body 21 in the longitudinal direction, h is the thickness (mm) of the main body 21, and E is the main body 21 (main body 21). It is the Young's modulus (MPa) of the constituent sheet).

When the resin composition shrinks in the conventional molding mold, stress is generated inside the resin composition. Due to this stress, the obtained resin molded product tends to have poor appearance such as cracks and sink marks. On the other hand, in the manufacturing method of the present embodiment, the second member 20 is deformed in the radial direction as the resin composition 50 shrinks. As a result, stress is less likely to occur inside the resin composition 50. By suppressing the generation of stress inside the resin composition 50, the resin molded body 51 is less likely to have an appearance defect.

Patent Document 1 describes that a rod-shaped resin molded body is produced by using a container body including an outer cylinder and an inner cylinder. However, in the container body of Patent Document 1, the inner cylinder is fitted into the outer cylinder. Therefore, the inner cylinder of Patent Document 1 cannot be deformed in the radial direction, and the generation of stress inside the resin molded product cannot be sufficiently suppressed.

(Embodiment 2)
The second member 20 of the first embodiment may not have the slit 25 as long as it can be deformed in the radial direction. As shown in FIG. 5, in the molding die 110 according to the second embodiment, the second member 20 does not have the slit 25. Except for the above, the structure of the molding die 110 is the same as that of the molding die 100 of the first embodiment. Therefore, the same reference numerals may be given to the elements common to the molding die 100 of the first embodiment and the molding die 110 of the present embodiment, and the description thereof may be omitted.

In the molding die 110, the shape of the second member 20 (main body portion 21) is not particularly limited as long as it is cylindrical, and is preferably cylindrical. In the molding die 110, the second member 20 (main body portion 21) preferably contains at least one selected from the group consisting of heat-resistant resin and aluminum from the viewpoint of facilitating deformation in the radial direction, and is preferably a fluororesin. , In particular PTFE.

In the present embodiment, when the resin composition after heat treatment is cooled inside the second member 20, the resin composition shrinks and the material itself constituting the main body 21 of the second member 20 shrinks, or the main body Strain occurs in the portion 21. As a result, the second member 20 can be deformed so as to follow the shrinkage of the resin composition. Since the second member 20 is deformed in the radial direction as the resin composition shrinks, stress is less likely to occur inside the resin composition. By suppressing the generation of stress inside the resin composition, the resin molded product is less likely to have a poor appearance.

When the resin composition is heat-treated, the resin composition tends to expand as the temperature rises. Therefore, when the molding die 110 of the present embodiment is used, it is necessary to adjust the filling amount of the resin composition so that the second member 20 is not significantly deformed by the expansion of the resin composition.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

(Example 1)
[Polymer (P)]
First, in an argon atmosphere at room temperature (20 ° C. ± 15 ° C.), 22.6 g of perfluoro-2-methylene-4-methyl-1,3-dioxolane (compound represented by the formula (M2)) was added to 1 of 50 mL. , 1,1,2,2,3,4,5,5-decafluoropentane (Bertrel XF manufactured by Mitsui-Kemers Fluoroproducts). While maintaining the argon atmosphere, 0.155 g of perfluorobenzoyl peroxide was added to the obtained solution, and the mixture was stirred and mixed. Next, dissolved oxygen was removed from the solution by the freeze degassing method. The solution was heated to 40 ° C. with stirring and reacted for 72 hours. The resulting reaction mixture was added to 300 mL of chloroform. The precipitate produced by this operation was collected by filtration. The obtained filter medium was a polymer of perfluoro-2-methylene-4-methyl-1,3-dioxolane (polymer (P)). The yield of the polymer (P) was 19.2 g, and the yield was 81.0%.

[Resin molded product]
Next, a first member having a tubular main body made of Hastelloy (see FIG. 1) and a sheet made of PTFE (thickness: 0.3 mm) were prepared. The longitudinal elastic modulus (Young's modulus) of the sheet was 500 MPa. Next, by bending the sheet, a tubular second member (see FIG. 1) having a main body and a slit was produced. In the second member, the length L1 of the main body portion in the circumferential direction was 180 mm. The width L2 of the slit was 12 mm. In the second member, the diameter of the virtual circle C defined by the inner peripheral surface of the main body was 67.8 mm. Next, a molding die was produced by arranging the second member inside the main body of the first member. Inside the first member, the main body of the second member was in contact with the main body of the first member. For this molding, a lid was attached to one end of the first member.

Next, a powdery resin composition composed of the polymer (P) was filled inside the second member. A lid was attached to the other end of the first member, and the inside of the main body of the first member was sealed. Next, the resin composition filled inside the second member was heat-treated. The heat treatment temperature was 260 ° C. The heat treatment time was 20 hours. The heat treatment melted the resin composition.

Next, the resin composition was cooled to room temperature (25 ° C.) by dissipating heat from the heat-treated resin composition. As a result, the resin composition was solidified inside the second member, and a rod-shaped resin molded body was obtained. At this time, the resin composition contracted in the radial direction as the temperature decreased. In the second member, the width of the slit decreased as the resin composition shrank. By reducing the width of the slit, the second member was deformed in the radial direction. The stress generated in the second member 20 due to the radial deformation of the second member 20 was 3.6 × 10 ^-5 MPa. The ratio (shrinkage ratio) of the difference between the volume of the resin composition at 260 ° C. and the volume of the resin molded product at 25 ° C. with respect to the volume of the resin composition at 260 ° C. was 1.6 vol%.

Next, the resin molded body was taken out from the molding die, and the appearance of the resin molded body was visually evaluated. The results are shown in Table 1. In Table 1, ◯ means that almost no cracks or sink marks could be confirmed in the resin molded product. Δ means that cracks and sink marks were hardly confirmed in the resin molded product, while a small amount of air bubbles were confirmed. X means that cracks and sink marks were confirmed in the resin molded product.

(Example 2)
A resin molded product was produced by the same method as in Example 1 except that the thickness of the sheet for forming the second member was changed to 0.8 mm. The appearance of the obtained resin molded product was visually evaluated. The results are shown in Table 1.

(Example 3)
A resin molded product was produced by the same method as in Example 1 except that the thickness of the sheet for forming the second member was changed to 1.0 mm. The appearance of the obtained resin molded product was visually evaluated. The results are shown in Table 1.

(Example 4)
A resin molded product was produced by the same method as in Example 1 except that a sheet made of aluminum (thickness: 0.2 mm) was used as the sheet for forming the second member. The appearance of the obtained resin molded product was visually evaluated. The results are shown in Table 1.

(Comparative Example 1)
A resin molded product was produced by the same method as in Example 1 except that a cylinder (thickness: 3 mm) made of Hastelloy was used as the second member. The cylinder had no slits and was rigid. Therefore, when the resin composition was cooled, the cylinder did not deform in the radial direction. The appearance of the obtained resin molded product was visually evaluated. The results are shown in Table 1.

As can be seen from Table 1, in Examples 1 to 4 using the second member that can be deformed in the radial direction, a resin molded product having an excellent appearance to the extent that cracks and sink marks can hardly be confirmed was obtained. A resin molded product having such an excellent appearance can sufficiently suppress air bubbles from being mixed into the optical member when the optical member such as POF is manufactured.

The molding die of this embodiment is suitable for producing a preform of an optical member such as a POF.

10 1st member 11 Main body 20 2nd member 21 Main body 25 Slit 50 Resin composition 51 Resin molded body 100, 110 Molding mold

Claims (16)

A molding die for molding a resin composition into a rod-shaped resin molded body.
The first tubular member and
A tubular second member arranged inside the first member and extending in the longitudinal direction of the first member, and
With
The second member is a molding die that is deformable in the radial direction. The molding die according to claim 1, wherein the second member is deformable in a direction away from the first member. The molding die according to claim 1 or 2, wherein the second member is made of a bendable sheet. The molding die according to any one of claims 1 to 3, wherein the second member has a slit. The molding die according to claim 4, wherein the slit extends from one end to the other end of the second member. The molding die according to claim 4 or 5, wherein the width of the slit is 1 mm to 80 mm. The molding die according to claim 1 or 2, wherein the second member has a cylindrical shape. The molding die according to any one of claims 1 to 7, wherein the second member contains at least one selected from the group consisting of a heat-resistant resin and a metal material. The molding die according to any one of claims 1 to 8, wherein the second member contains polytetrafluoroethylene. The molding die according to any one of claims 1 to 9, wherein the first member includes a metal material. To perform heat treatment on the resin composition filled inside the second member of the molding mold according to any one of claims 1 to 10.
Cooling the resin composition after the heat treatment and cooling the resin composition so that a rod-shaped resin molded body can be obtained inside the second member.
A method for producing a resin molded product, including. The resin composition is solid at room temperature and
The production method according to claim 11, wherein the resin composition is softened by the heat treatment. The production method according to claim 11 or 12, wherein the heat treatment temperature is 120 ° C to 350 ° C. The production method according to any one of claims 11 to 13, wherein the resin composition contains a polymer having a structural unit represented by the following formula (1).

[In the formula (1), R _ff ^{1 to} R _ff ⁴ independently represent a fluorine atom, a perfluoroalkyl group having 1 to 7 carbon atoms, or a perfluoroalkyl ether group having 1 to 7 carbon atoms. R _ff ¹ and R _ff ² may be connected to form a ring. ] The manufacturing method according to claim 14, wherein the structural unit is represented by the following formula (2).

A molding die used in a method of molding a resin composition into a rod-shaped resin molded body.
The method comprises cooling the heat treated resin composition to room temperature.
The molding mold is
The first tubular member and
A tubular second member arranged inside the first member and extending in the longitudinal direction of the first member, and
With
The second member is a molding mold that contains the resin composition and deforms in the radial direction together with the resin composition when the temperature of the heat-treated resin composition drops to room temperature.

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