JPH04357014A - Plastic vessel and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide heat-moldings consisting mainly of polycarbonate with deep bottom that can not be manufactured by a prior art. CONSTITUTION:In the case of molding a sheet consisting mainly of polycarbonate, by making most suitable the moving timing of a male mold and female mold, timing of blowing out of pressurized air from the mold and/or timing of discharge to the outside of the mold, and a combination of the conditions of mold intervals between the male mold and female mold, a heat-molding can be manufactured that can be brought into a practical use.

Description

Description: [0001] The present invention relates to a deep-bottomed packaging container formed from a sheet mainly made of polycarbonate, and a method for manufacturing the same. 2. Description of the Related Art Thermoformed containers mainly made of polycarbonate (hereinafter sometimes abbreviated as PC) are used as containers with excellent flavor retention properties, such as for food packaging. All of these containers have shallow bottoms;
Many commonly used containers have a ratio T/D of the longest diameter (D) of the opening to the depth (T) of 0.3 to 0.5 or less. The reason why the bottom of the container is so shallow is that when a PC sheet is molded using the normal thermoforming method, as the T/D increases, the container becomes extremely uneven in thickness and breaks during molding, making it impractical for practical use. This is because durable molded products cannot be manufactured. SUMMARY OF THE INVENTION An object of the present invention is to provide a thermoformed plastic container mainly made of polycarbonate, which has a deep bottom and is not extremely uneven in thickness. Another object of the present invention is to provide a novel manufacturing method for industrially advantageous manufacturing of the container of the present invention without causing breakage during molding. Further objects and advantages of the invention will become apparent from the following description. Means for Solving the Problems The above objects and advantages of the present invention are as follows: (A) the container material is mainly made of polycarbonate, and (B) the longest diameter versus depth of the container opening is This is achieved by a thermoformed plastic container characterized by a ratio in the range 0.7 to 2.5. [0007] Further, according to the present invention, the container of the present invention comprises:
(1) providing a preheated sheet of primarily polycarbonate; (2) approaching one surface of the sheet with a male plug from a direction substantially perpendicular to the surface; and applying a male plug to the other surface of the sheet. (3) first bring the male plug into contact with one surface so that the preheated sheet begins to deform with the male plug; in contact with the other surface, and then connect the male plug and female mold until the distance between the outer bottom of the male plug and the inner bottom of the female mold is 20 mm or less, or when the male plug is finally molded. (4) Blow out pressurized air through a small hole provided on the outer surface of the male plug, or use a female plug. The outer surface of the male plug and the inner surface of the female plug are brought into close contact with each other by sandwiching the outer surface of the male plug and the inner surface of the female plug between sheets, either by ejecting air under reduced pressure through a small opening provided on the inner surface of the plug, or by performing both of these steps together. It can be manufactured by The present invention will be explained in detail below. The sheet prepared in step (1) of the method of the present invention is mainly made of polycarbonate (PC). This also means that the plastic component of the material is mainly composed of PC. Examples of secondary plastic components other than PC include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), and polybutylene naphthalate. Aromatic polyesters such as (PBN); copolymers of acrylonitrile, butadiene, and styrene (ABS), polymethyl methacrylate, nylon 6, nylon 66, nylon 46, and the like are used. Among these, aromatic polyesters are preferred. [0010] One or more types of such secondary plastic components can be used. The secondary plastic component is preferably 20% by weight or less, more preferably 10% by weight or less, based on the total weight of the PC and secondary plastic components, based on the total weight of the PC and secondary plastic components.
It is used in less than % by weight. [0011] In addition to the above-mentioned plastic components, the sheet material can also contain lubricants such as fine talc, clay, calcium carbonate, zeolite, and titanium oxide. Such a lubricant preferably accounts for 5% by weight of the total material.
The content is more preferably 1% by weight or less. The thickness of the sheet used in step (1) of the present invention is preferably in the range of 0.05 to 2 mm;
．． More preferably, it is in the range of 1 to 1.5 mm. [0013] The sheet may have a flat surface or a previously textured surface. It is preferable to have the latter surface. Prior to forming, the sheet is preheated using, for example, a hot plate, an infrared heater, or hot air to enable thermoforming. The preheated sheet (S) is then subjected to step (2).
) and then thermoformed. The preheating temperature of the sheet (S) is preferably 150 to 230°C, more preferably 170 to 21°C.
It is 0°C. In step (2), a male plug is approached to one surface of the sheet (S) from a direction substantially perpendicular to the surface, and a male plug is brought to the other surface of the sheet (S), facing the male plug. and bring the female mold closer. Next, in step (3), the male plug (M) is brought into contact with one surface, and then the female plug (F) is brought into contact with one surface.
to the other surface. [0018] The above-mentioned timing of contact in step (2) and step (3) is important. Without such contact timing, a container that can be put to practical use cannot be obtained. For example, if F approaches S first, then M approaches and contacts S, or if M and F contact S almost simultaneously, the part near the opening of the molded product is likely to break. Further, even if a molded article is obtained without breaking, the thickness of the molded article at this point becomes extremely thin, and a molded article that can withstand practical use cannot be obtained. On the other hand, if M approaches S and moves a considerable distance while deforming S, or after moving a predetermined distance and stopping, F comes into contact with S, the bottom of the molded article The thickness becomes thinner, or wrinkles appear in the opening, and in this case, a molded product that can be put to practical use cannot be obtained. [0021] When performing the molding of the present invention, M and F may be at room temperature or may be heated. Preferably, M or F or both M and F are heated to 50 to 150°C, more preferably 70 to 120°C. In step (3), a male plug (M
) and the female type (F) so that the distance between the outer bottom of the male plug (M) and the inner bottom of the female type (F) is 20 mm or less, preferably 10 mm or less, or the male plug (M)
The steps are allowed to proceed in an intersecting manner until they reach a depth of at least 70%, preferably at least 90%, of the depth of the container to be finally formed. After M and F reach the positional relationship as described above, in step (4) pressurized air is blown out through the small opening provided on the outer surface of M, or the small opening provided on the inner surface of F is blown out. The sheet is brought into close contact with the inner surface of F by exhausting the air under reduced pressure through the holes, or by performing both of these methods together. The microapertures preferably have a diameter of about 1 mm or less. As mentioned above, the timing of blowing or exhausting air is important. For example, if the timing of blowing air is too early from M, the thickness of the bottom of the molded product will become too thin, and if the timing of blowing air from M or discharging air from F is too late, the preheated sheet will be damaged. solidifies and the mold adhesion effect by blowing becomes ineffective. Regarding the positional relationship between M and F,
It is also desirable to consider the positional relationship at the time when the molding stops and molding is completed. That is, at the time when M and F stop, the outer surface of M and the inner surface of F are less than 2 mm, minus the thickness of the sheet between these two surfaces.
In particular, it is preferable that they be separated by a distance of 1 mm or less. [0027] Also, the distance between the outer bottom of M and the inner bottom of F is 1
It is preferably 0 mm or less, more preferably 5 mm or less. The movement of M and F is carried out by a hydraulic mechanism or the like, similar to normal thermoforming (air pressure forming, vacuum forming, etc.). The speed of movement is also within the range used for normal thermoforming. Further, like a normal thermoforming mechanism, the open end of F generally does not advance beyond the position of S. Thus, according to the present invention, as described above,
A thermoformed plastic container is provided in which the container opening has a longest diameter to depth ratio in the range of 0.7 to 2.5. The preferred range of the above ratio is from 0.7 to 1.5. Note that the longest diameter (D) here refers to the following measured value. [0031] The thermoformed container has a shape such as a cup, box, or tray. The opening has a shape such as a circle, an ellipse, a polygon, each part of the polygon is curved, or a combination thereof. Among these various shapes, among the distances between two points variously measured between the insides of the openings within the virtual plane of the container opening, the largest measured value, such as the diameter in the case of a circle, is referred to as the longest diameter. Further, the depth (T) refers to the maximum value of the perpendicular lines drawn from the imaginary plane at the opening of the container to the bottom. [Examples] The present invention will be explained in more detail below with reference to Examples and Comparative Examples. Example 1 A sheet made of PC with a thickness of 0.5 mm and embossed to a depth of about 10 μm on its entire surface was preheated using an infrared heater. Next, a cup-shaped male plug (MC-1)
was brought close to and in contact with the sheet, and a cup-shaped female mold (FC-1) was also brought close to the sheet. M.C.
-1 has advanced to a position approximately 1/2 of the cup depth T while deforming the sheet beyond the sheet surface, when the FC
-1 was also brought into contact with the sheet. Furthermore, MC-1, FC-
One phase was allowed to cross and proceed, and when the outer bottom of MC-1 and the inner bottom of FC-1 came close to each other by about 5 mm, pressurized air was blown out from MC-1 to bring S into close contact with FC-1. In addition, MC-
The distance between the outer surface of FC-1 and the inner surface of FC-1 was approximately 0.7 mm after subtracting the sheet thickness. [0035] FC-1 used at this time was heated to a temperature of 90°C, and MC-1 was heated to about 50°C. Among the various dimensions of the cup-shaped container thus obtained, the depth (T) and the longest diameter (
D) were 60 mm and 65 mm, respectively, and the others were as shown in Table 1. [0036] The positions A, B, and C for measuring the thickness of the molded product listed in Table 1 are as follows. A: A position 10 mm inside the opening end of the upper part of the molded product, B: An intermediate position between the opening and the bottom of the molded product, C: A position 10 mm from the bottom of the molded product on the opening side, [0037] To measure the thickness: Using a micrometer, measurements were taken at two opposing positions at arbitrary positions in the circumferential direction and averaged. In addition, mold traceability was determined visually by determining how faithfully the female mold shape was traced. [0038]For moldability, findings related to molding were noted. For each of the following examples and comparative examples, the same measurement values as above,
I wrote down my findings, etc. Comparative Example 1 A test was conducted using the same sheet, mold, and mold movement conditions as those used in Example 1. However, the timing of blowing out pressurized air from the MC was started when the distance between the outer bottom of the MC and the inner bottom of the FC was about 50 mm. The results are in Table 1
It was shown to. Example 2 A 0.9 mm thick sheet made of a polymer mixture of 90% by weight of PC and 10% by weight of PET and embossed to a depth of about 8 μm on the entire surface was preheated using an infrared heater, and then heated in a cup. Male plug MC-2 and female FC-2
It was molded using. That is, first, the MC-2 is brought close to and in contact with the sheet, and the FC-2 is also brought close, and the MC-2 moves beyond the sheet surface and deforms the sheet until it reaches a position approximately 2/3 of the length of the cup depth T. At this point, FC-2 was also brought into contact with the sheet, and MC-2 and FC-2 were further advanced in a mutually intersecting manner, and when the outer bottom of MC-2 and the inner bottom of FC-2 came close to about 3 mm apart, FC-2 was brought into contact with the sheet. Air was exhausted through a small hole provided on the inner surface of -2, and the sheet was brought into close contact with the inner surface of FC-2. [0041] Also, the temperature of FC-2 used at this time was about 90
℃, the temperature of MC-2 was about 50℃. [0042] Also, T and D of the obtained container were each 8.
They were 0 mm and 63 mm (D/T≈0.79). The results are shown in Table 1. Comparative Example 2 The same sheet and female mold as those used in Example 1 and the same FC-1 were used. However, only the male plug was made smaller. That is, the size was such that when the FC-1 and the plug finished molding and stopped, the distance between the outer surface of the plug and the inner surface of the FC-1 was 5 mm, not including the sheet. Other molding conditions were the same as in Example 1. The results are shown in Table 1. Comparative Example 3 Molding was carried out using the same sheet as used in Example 1 and the same molds MC-2 and FC-2 as used in Example 2. First, the sheet was preheated with an infrared heater, and then the MC-2 was first moved to advance while deforming the sheet, and then stopped after traveling a predetermined distance. After that, FC-
2 was moved, and the MC-2 was moved to a predetermined position while deforming the sheet by crossing each other, and then pressurized air was blown out from the MC-2 to bring it into close contact with the inner surface of the FC-2. Other molding conditions are the same as in Example 2. The results are shown in Table 1. Comparative Example 4 Same as Comparative Example 3, the same sheet as that used in Example 1, and the same molds as MC-2 and FC used in Example 2.
-2. After preheating the sheet with an infrared heater, FC-2 is first moved to the nearest position of the preheated sheet, then MC-2 is moved, and the sheet is deformed by intersecting with FC-2. As the engine progressed, the FC-2 was evacuated when the outer bottom of the MC-2 and the inner bottom of the FC-2 became approximately 15 mm apart. Other molding conditions were the same as in Example 2. The results are shown in Table 1. Example 3 A sheet having a thickness of 1.2 mm was prepared by adding 1.5% by weight of Celite to a polymer blended with 93.5% by weight of PC and 5% by weight of PEN. Next, after preheating the sheet with an infrared heater, a male plug (MB) is used to produce a box-shaped molded product.
-1) and a female mold (FB-1). The timing of movement of MB-1 and FB-1 was the same as that of MC-1 and FC-1 in the first embodiment. MB- when molding is completed and MB-1 and FB-1 have stopped
The distance between the outer surface of FB-1 and the inner surface of FB-1 was approximately 0.5 mm after subtracting the sheet thickness. 0052
]Also, the temperature of MB-1 is 60℃, and that of FB-1 is 10℃.
It was 0°C. The T of the obtained container is 80 mm, and the D is 85.
It was mm. The results are shown in Table 1. Comparative Example 5 A sheet with a thickness of 0.3 mm was prepared from a polymer blend consisting of 70% by weight of PC and 30% by weight of PBT. Next, after preheating the sheet, it was molded under the same conditions as in Example 3 using MB-1 and FB-1. The results are shown in Table 1. Comparative Example 6 Using the same sheet as that used in Example 2, a cup-shaped male plug (MC-3) and a female plug (FC-3) were prepared.
It was molded using. The molding conditions were the same as in Example 2. T of the obtained container is 150 mm, D is 50 mm, and T/D
was 3. The results are shown in Table 1. [Table 1] [Effects of the Invention] The molded products obtained by the present invention are excellent in applications that require heat resistance and, in some cases, transparency, such as foods, such as beverages and processed foods. It can be practically useful as a packaging container.

Claims (6)

[Claims] Claims: 1. A thermoplastic container, characterized in that (A) the container material primarily consists of polycarbonate, and (B) the ratio of the longest diameter to the depth of the container opening is in the range of 0.7 to 2.5. Molded plastic container. Claim 2: The plastic component of the container material is 80 to 100% by weight of polycarbonate and 0% of aromatic polyester.
2. The plastic container of claim 1 comprising ˜20% by weight. 3. The plastic container according to claim 2, wherein the aromatic polyester comprises at least one polymer selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate. 4. (1) providing a preheated sheet of primarily polycarbonate; (2) approaching one surface of the sheet with a male plug from a direction substantially perpendicular to the surface; and (3) First, the male plug was brought into contact with one surface, and the preheated sheet began to deform with the male plug. After that, the female mold is brought into contact with the other surface, and the male plug and the female mold are connected until the distance between the outer bottom of the male plug and the inner bottom of the female mold is 20 mm or less, or the male plug (4) Pressurized air is introduced through a small hole provided on the outer surface of the male plug. Blow out or
2. The thermoformed sheet according to claim 1, characterized in that the sheet is brought into close contact with the inner surface of the female mold by exhausting air under reduced pressure through small openings provided on the inner surface of the female mold, or by performing both of these steps together. A method for manufacturing plastic containers. 5. The method of claim 4, wherein the sheet prepared in step (1) is an embossed sheet. [Claim 6] In step (4), the distance between the outer surface of the male plug and the inner surface of the female plug is finally determined by the following relational expression: L-(
5. The method according to claim 4, wherein L is the distance (mm) between the outer surface of the male plug and the inner surface of the female plug.