JP2024020128A - Method for manufacturing resin container, and resin container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a resin container having a novel texture and excellent appearance.

SOLUTION: A method for manufacturing a bottomed cylindrical resin container made of a resin material containing polyethylene terephthalate (PET) includes: a preform production step (s1) to produce a preform by injection molding; a crystallization step (s2) to crystallize PET in at least some areas of the preform; and a blow molding step (s4) in which a resin container is molded by stretch blow molding the preform. In the preform production step, the resin material including acrylic resin is used, with PET as a main raw material. In the blow molding step, a region made of PET crystallized in the crystallization step and a pearl-like region that is white and more glossy than the region made of crystallized PET are mixed on a surface of the resin container.

SELECTED DRAWING: Figure 2

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a method for manufacturing a resin container and a resin container.

Polyethylene terephthalate (hereinafter sometimes referred to as "PET") has properties such as heat resistance, cold resistance, chemical resistance, and excellent strength. Moreover, for this reason, PET is often used as containers for beverages and cosmetics.

Incidentally, in addition to the above-mentioned functional properties, resin containers such as cosmetic containers are also required to have excellent aesthetic properties. Factors that affect the aesthetic appearance of resin containers include "texture," such as the degree of light reflection on the container surface, transparency, touch, and color. For example, some containers made primarily of PET have a so-called "pearl-like" texture. Pearl tone has a white, smooth, and glossy texture, and examples of cosmetic containers exhibiting this pearl tone include the cosmetic bottle described in Patent Document 1 below.

The cosmetic bottle described in Patent Document 1 is made by stretching a resin material made of PET containing an acrylic resin (for example, polymethyl methacrylate resin (hereinafter sometimes referred to as "PMMA")) as a raw material. It is blow molded. The cosmetic bottle described in Patent Document 1 has a three-dimensional flow pattern by adjusting the mixing ratio of PET and acrylic resin during manufacture, the temperature during stretch blow molding, and the total stretch ratio. It also has a pearl-like surface luster.

Further, as a resin container which uses PET as the main raw material but has a texture different from pearl tone, for example, there is a container made of crystalline PET. Although crystalline PET has a white color similar to pearl-like, the surface gloss and texture are frosted glass-like, giving it a texture that can be described as ``matte,'' ``matte,'' or ``chic.'' It has an aesthetic appearance that is different from that of smooth, shiny pearls. As a resin molded product made of this crystalline PET, there is a multilayer container described in Patent Document 2 below. In the multilayer container described in Patent Document 2, the body of the inner layer is made of crystalline PET. Patent Document 2 states that a molded product obtained by injection molding PET becomes transparent when rapidly cooled, and that it is either slowly cooled in the atmosphere, or once rapidly cooled and made transparent, it is heated to a high temperature. It is stated that when the surface is reheated, a whitening phenomenon occurs due to crystallization. Further, Patent Document 2 describes that the high temperature (surface temperature) due to reheating is 70° C. to 200° C., which is between the glass transition point and the crystallization temperature.

Utility Model Publication No. 54-133969 Utility Model Publication No. 58-112949

Resin containers that are stretch-blow molded using PET as the main raw material can have a pearlescent or white color made of crystalline PET depending on the stretch-blow molding method, such as the content of additives and the temperature during molding. . These containers are either pearl-like or crystalline PET as a whole, or white as in the case of the cosmetic bottle described in Patent Document 1 or the inner layer of the multilayer container described in Patent Document 2. This is a mixture of visible areas and transparent areas.

However, the conventional resin containers described in Patent Documents 1 and 2 have a texture of either a pearl-like region or a region made of crystalline PET, except for the transparent region originally made of PET. It has become. For this reason, in today's world, where diversity is required not only for people but also for various objects, it can be said that the texture of conventional resin containers is monotonous.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for manufacturing a resin container that has a novel texture different from conventional ones and is excellent in appearance, and to provide a resin container.

One aspect of the present invention for achieving the above object is a method for manufacturing a bottomed cylindrical resin container made of a resin material containing PET, comprising:
a preform production step of producing a preform by injection molding;
a crystallizing step of crystallizing the PET in at least some regions of the preform;
a blow molding step of molding the preform into a resin container by stretch blow molding,
In the preform production step, a resin material containing acrylic resin is used with the PET as the main raw material,
In the blow molding step, a region made of PET crystallized in the crystallization step and a pearl-like region that is white and more glossy than the region made of crystallized PET are mixed on the surface of the resin container. let,
The method of manufacturing a resin container is characterized by the following.

In the preform manufacturing step, the preform having different thickness depending on the region may be manufactured by injection molding, and the PET in the thick region may be crystallized.

In the preform manufacturing step, the preform having a sloped wall thickness is manufactured by injection molding, thereby changing the crystallinity of the PET in stages according to the wall thickness. You can also.

In the crystallization step, the produced preform may be heated to crystallize the PET in the heated region.

Another aspect of the present invention is a method for manufacturing a bottomed cylindrical resin container made of a resin material containing PET, comprising:
a preform production step of producing a preform by a process including injection molding;
a blow molding step of molding the preform into a resin container by stretch blow molding,
In the preform manufacturing step,
A first step of molding a single-layer preform by injection molding a resin material containing acrylic resin using PET as the main raw material;
By injection molding a resin material made of PET on the inner or outer side of the preform, an inner layer or an outer layer made of PET is laminated on the preform produced in the first step to form a two-layer structure. performing a second step of molding the preform;
In the blow molding step, a region made of crystallized PET is formed in a region corresponding to the single-layer preform, and a region made of crystallized PET is formed in white in a region corresponding to the inner layer or outer layer laminated in the second step. forming a pearl-like area that is more lustrous than the area made of molten PET,
It is also possible to provide a method for manufacturing a resin container characterized by the following.

Alternatively, a method for manufacturing a bottomed cylindrical resin container made of a resin material containing PET,
a preform production step of producing a preform by a process including injection molding;
a blow molding step of molding the preform into a resin container by stretch blow molding,
In the preform manufacturing step,
A first step of molding a single layer preform by injection molding a resin material made of PET;
By injection molding a resin material containing acrylic resin using PET as the main raw material, an inner layer or an outer layer made of PET is added to the preform produced in the first step on the inner or outer surface of the preform. a second step of laminating and forming a two-layer preform;
In the blow molding step, a region made of crystallized PET is formed in a region corresponding to the inner layer or the outer layer, and a white region made of the crystallized PET is formed in a region corresponding to the single layer preform. forming a pearl-like area with more luster than the other areas,
It is also possible to provide a method for manufacturing a resin container characterized by the following.

In any of the above resin container manufacturing methods, the PET includes one or more of petroleum-derived virgin PET, recycled PET, and biomass PET, and the acrylic resin contains petroleum-derived virgin PET, recycled PET, and biomass PET. The present invention may also be a method for manufacturing a resin container containing either virgin acrylic, recycled acrylic, or both.

In any of the resin container manufacturing methods described above, the resin material for injection molding the preform having a region formed of the crystallized PET contains polymethyl methacrylate resin in PET; The mass percentage of the PET contained in the material may be 90% or more and 99% or less.

Aspects of the present invention also include a resin container having an opening at the tip, and the resin container includes:
Contains acrylic resin with PET as the main component,
A mixture of crystallized PET and a white region that is glossier than the region made of the crystallized PET,
The region where the crystallized PET exists is formed thicker than other regions;
The resin container is characterized by:

A resin container may be formed in which a region having a slope in wall thickness is formed, and in the region having a slope in wall thickness, the degree of crystallinity of the PET gradually increases as the wall thickness increases. can.

It has a two-layer structure in which a first layer made of PET and a second layer mainly composed of PET and containing an acrylic resin are laminated in the thickness direction,
The first layer has a region made of crystallized PET,
The second layer is white and formed into a pearl-like shape that is more glossy than the region made of crystallized PET.
It may also be a resin container characterized by this.

According to the present invention, there are provided a method for manufacturing a resin container that has a novel texture different from conventional ones and is excellent in appearance, and a resin container. In addition, other effects will be clarified in the following description.

FIG. 3 is a diagram showing a resin container that can be manufactured by the manufacturing method according to the first example. It is a figure which shows the resin container which can be manufactured by the manufacturing method based on 1st and 2nd Example. It is a figure which shows the resin container which can be manufactured by the manufacturing method based on 3rd Example. It is a figure showing the procedure of the manufacturing method of the resin container concerning a 1st example. FIG. 3 is a diagram showing a preform molded in the resin container manufacturing process in the resin container manufacturing method according to the first embodiment. 1 is a photograph showing a resin container manufactured by the resin container manufacturing method according to the first example. FIG. 2 is an external view of a sample for examining PET crystallization conditions. It is a photograph showing the state of crystallization of PET in the above sample. It is a figure which shows the procedure of the manufacturing method of the resin container based on 2nd Example. It is a figure which shows the procedure of the manufacturing method of the resin container based on 3rd Example. FIG. 7 is a diagram illustrating a two-layer preform that is molded in the process of manufacturing a resin container in a method for manufacturing a resin container according to a third embodiment.

Embodiments of the present invention will be described with reference to the accompanying drawings. In addition, in the drawings used for the following explanation, the same or similar parts may be given the same reference numerals and redundant explanations may be omitted. Parts marked with reference numerals in one drawing may not be provided with reference numerals in other drawings if unnecessary.

===Example===
In the method for manufacturing a resin container according to an embodiment, a bottomed cylindrical integral resin container has a novel texture in which a region having a pearl-like texture and a region made of crystalline PET coexist. It can be made. 1A to 1C illustrate resin containers (hereinafter referred to as "containers") (1a to 1c) manufactured by the manufacturing method according to the example. In FIGS. 1A to 1C, partially cutaway perspective views of containers (1a to 1c) are shown, and the cross sections are indicated by diagonal hatching.

The containers (1a to 1c) illustrated in FIGS. 1A to 1C have the same external shape, and include a cylindrical neck portion 2 with a male thread 21 formed on the outer periphery, and a bottomed cylinder whose diameter is enlarged relative to the neck portion 2. It consists of a container body 3 with a shape. Here, if the direction of the cylindrical axis 100 is the up-down direction and the bottom 4 is the downward direction, the container body 3 is composed of the bottom 4 and the body 5 serving as the side wall, and the lower end of the neck 2 is connected to the shoulder 6. It is continuous to the upper end of the body part 5 through. Each of the containers (1a to 1c) has a container body 3 in which a pearlescent region 11 and a region 12 made of crystalline PET coexist.

In the container 1a illustrated in FIG. 1A, the upper end side of the container body 3 is shaped to have a pearlescent finish, and from the base point 12a on the way downward to the bottom 4, gradually move downward from the base point 12a. There is a region 12c where the crystallinity of PET increases. PET is almost completely crystallized at the lower end 12b of this region 12c, and the completely crystallized state reaches the bottom 4.

In FIG. 1A, a region 11 having a pearlescent texture is shown by halftone dot hatching. Note that the area 11 having an actual pearl-like texture is white and glossy. Further, in the region 12c where the degree of crystallinity gradually increases, the thickness gradually increases from the top to the bottom with the degree of crystallinity. In the region 12c where the degree of crystallinity gradually increases, the lustrous pearl-like texture gradually becomes cloudy and becomes matte from the top to the bottom. . In the figure, this region 12c is shown in a gradation display so that the color becomes darker as the degree of crystallinity increases, and the completely crystallized region 12d is shown by mesh hatching.

In the container 1b shown in FIG. 1B, a region 12 made of crystalline PET and a pearl-like region 11 coexist with a boundary in the container body 3. In the container 1b shown in FIG. 1B, an annular region 11 shaped like a pearl and an annular region 12 made of crystalline PET are formed in a stripe shape in order from the upper end of the container body 3 downward. has been done. In the figure, the pearlescent region 11 is shown by halftone dot hatching, and the region 12 made of crystalline PET is shown by mesh hatching.

The container 1c shown in FIG. 1C has a container body 3 having a two-layer structure in which a region 11 having a pearl-like texture and a region 12 made of crystalline PET are laminated in the thickness direction. In the illustrated example, the outer layer of the container body 3 (hereinafter sometimes referred to as the "outer layer 8") is a layer having a pearl-like texture, and the inner layer (hereinafter referred to as the "inner layer 7") is a layer with a pearl-like texture. ) is formed of crystalline PET, and when the body 5 is viewed from the outside, the cloudy inner surface on the back side can be seen through the pearl-like surface. In the figure, the pearlescent region 11 is shown by halftone dot hatching, and the region 12 made of crystalline PET is shown by mesh hatching.

Below, first to third examples will be described as methods for manufacturing the containers (1a to 1c) shown in FIGS. 1A to 1C, respectively.

===First embodiment===
<Container manufacturing procedure>

With the manufacturing method according to the first embodiment, the containers (1a, 1b) shown in FIGS. 1A and 1B can be manufactured. Here, the manufacturing procedure of the container 1a shown in FIG. 1A will be described. The manufacturing method according to the first embodiment is the well-known "injection blow method." That is, the container 1a is produced through an injection molding process and a stretch blow molding process. Further, the manufacturing method according to the first embodiment is also a so-called "cold parison method" in which a preform molded by injection molding is cooled and then a stretch blow molding process is performed on the preform.

FIG. 2 shows the steps of the manufacturing method according to the first embodiment. Further, FIG. 3 shows a cross-sectional shape of a preform 30 that is the origin of the container 1a. As shown in FIG. 3, the preform 30 is composed of a neck portion 32 around which a male thread 31 is formed, and a test tube-shaped main body portion 33, and this main body portion 33 is stretch-blow molded to form a container 1a. This becomes the container body 3. The main body portion 33 extends through a cylindrical region (hereinafter sometimes referred to as “cylindrical portion 34”) continuous to the lower end of the neck portion 32, and reaches a hemispherical bottom portion 35 that is convex downward. The cylindrical portion 34 of the preform 30 corresponds to the body portion 5 of the container 1a, and a region 36 with an inclined wall thickness is formed in the cylindrical portion 34. It continues to the upper end of the bottom part 35 while maintaining the same.

As shown in FIG. 2, the manufacturing method according to the first embodiment first includes a step of injecting molten resin into a mold (s1), and a subsequent cooling step (s2). A preform 30 is produced. Next, the preform 30 is heated to enable stretch blow molding (s3), and the preform 30 is stretch blow molded to form the container 1a (s4).

Specifically, in the injection step (s1), a preform is produced using a resin material containing, for example, 99 wt% PET and 1 wt% PMMA (for example, 60N, LP-1: manufactured by Asahi Kasei Corporation), which is an acrylic resin. 30 is injection molded. Note that recycled PET was used as the PET. Recycled PET is made by processing molded products (PET bottles, etc.) collected as recycled resources into pellets as raw materials for other molded products (for example, NA-BT7906: manufactured by Kyoei Sangyo Co., Ltd., R100: manufactured by SK Chemical Co., Ltd.), which is a so-called "eco material".

In the first embodiment, a mold for forming the preform 30 has a cavity for forming a region 36 with a sloped wall thickness, and a 280° C. mold made of the above-mentioned resin material is placed inside the mold. After injecting the molten resin (s1), the injection molded molten resin is cooled (s2).

The method for cooling the molten resin is to cool the mold to a predetermined temperature (e.g. 25°C) by introducing a cooling medium (water, oil) into the flow path provided in the mold, and to A method (quenching) of rapidly cooling the molten resin to a predetermined temperature (e.g., 70°C, which is the glass transition point of PET) by maintaining it in the mold for a predetermined time (e.g., 120 seconds), and The molten resin is maintained in the mold for a predetermined time (for example, 15 seconds), and when the molten resin solidifies and becomes ready to be taken out as the preform 30, the mold is opened and the preform 30 is placed in the atmosphere for a predetermined time. There is a method (slow cooling) in which the preform 30 is gradually cooled by dissipating heat for a period of time (for example, 720 seconds). In the manufacturing method according to the first embodiment, in the process of cooling the molten resin, the PET in the region having a predetermined thickness or more is crystallized.

In the method for manufacturing a container according to the first embodiment, a preform 30 is formed in a region 36 where the wall thickness is sloped so that the degree of crystallinity gradually increases as the wall thickness increases. For example, if a resin material in which recycled PET and PMMA are mixed at a mass ratio of PET:PMMA=99:1 is used as the raw material, and the preform 30 is molded by rapidly cooling the molten resin, the thickness will be approximately 3 mm. Crystallization is observed in some regions, and almost complete crystallization occurs in regions where the thickness is 4 mm or more. Note that areas where crystalline PET exists can be visually confirmed as cloudy areas, and in areas with low crystallinity, cloudy points are dispersed in whitish transparent areas. In regions with high crystallinity, there are no transparent parts and the entire region is cloudy.

Next, the preform partially made of crystalline PET as described above is heated to a deformable state in the subsequent stretch blow molding step s3 (s3). The heating temperature is about 80°C to 160°C. In the stretch-blowing step (s4), the preform 30 is blow-molded at a predetermined stretch ratio (for example, 1.1 times or more). As a result, the region where PET is crystallized in the preform 30 is maintained as it is in the container 1a, and the non-crystallized region is shaped to have a white, glossy "pearl-like" texture.

FIG. 4 shows a photograph of the container 1a produced according to the first example. Note that FIG. 4 shows a state when the container 1a is cut along a plane including the cylindrical shaft 100, and the inner surface of the container 1a in the cross section is shown by a chain line. As shown by this cross-sectional shape, the thickness of the body 5 of the container 1a is not uniform, and the thickness increases from the top to the bottom (hereinafter referred to as the "slanted region 51 (12c)"). ) and then reaches the bottom 4.

As shown in FIG. 1A, the inclined region 51 (12c) corresponds to the region 36 in the cylindrical portion 34 of the preform 30 where the wall thickness is inclined, and the crystallinity of PET is increased from the top to the bottom. becomes a region 12c where the height gradually increases. In the container 1a, a region 11 having a pearlescent texture extends from the upper end of the body 5 to the upper end 12a of this inclined region 51 (12c). A region 54 from the top end 12a to the bottom 4 of the inclined region 51 (12c) is the region 12 where crystalline PET exists. In the inclined region 51 (12c), the gloss gradually disappears from the upper end 12a to the lower end 12b, and in the region 53 from the lower end 12b of the inclined region 51 (12c) to the bottom 4, it is entirely formed of cloudy crystalline PET. This is the area 12d where the image is displayed.

In this way, in the manufacturing method according to the first embodiment, the region 12 made of crystalline PET in the container 1a is controlled by adjusting the thickness of the preform. Therefore, the manufacturing method according to the first example can also be applied to manufacturing the container 1b shown in FIG. 1B.

The containers (1a, 1b) manufactured by the container manufacturing method according to the first embodiment have a region 11 having a pearl-like texture and a region 12 made of crystalline PET on the surface of the integral molded product. It has a novel texture that is a mixture of Further, according to the manufacturing method according to the first embodiment, by providing the inclined region 51 (12c) in the preform 30, a unique gradation changing from a pearl tone to a cloudy state made of crystalline PET is produced. It is also possible to produce a container 1a having a texture.

Furthermore, since it is difficult to control the wall thickness of the containers (1a, 1b) during stretch blow molding (s4), the manufacturing method according to the first embodiment uses injection molding, which allows precise control of the wall thickness. The reform 30 is molded, and the degree of crystallinity is controlled according to its wall thickness at the stage of the preform 30. That is, in the manufacturing method according to the first example, PET in any region of the container (1a, 1b) can be crystallized with high precision. The mechanism by which thicker areas crystallize is that when the molten resin cools down after injection molding, it is difficult for the thicker areas to dissipate heat, and the temperature at which PET crystallizes is maintained for a long period of time. You can think of it as a way of becoming.

<PET crystallization conditions>
As described above, in the container manufacturing method according to the first embodiment, a portion of the container can be formed from crystalline PET by controlling the thickness of the preform. By the way, PET, which is the main raw material of the container manufactured by the method according to the example, is supplied as pellets, and depending on the origin, the pellets include virgin PET, biomass PET, etc. in addition to the above-mentioned recycled PET. . Virgin PET is manufactured using petroleum-derived monoethylene glycol (MEG) as a crude raw material (for example, PIFG-10, EFG70: manufactured by Bell Polyester Products Co., Ltd.). Biomass PET is a product that replaces MEG and terephthalic acid (TPA) with plant-based raw materials, and is manufactured by refining plant-derived materials (sugar cane residue (molasses), etc.) and is used as MEG and TPA. (For example, BF3067B, N1B: manufactured by Indrama Ventures).

In this way, there are multiple types of PET with different origins. Therefore, we investigated conditions for crystallizing PET while using different types of PET. Specifically, injection molded products of predetermined shapes were produced as samples, each having a different origin of PET and different cooling methods. Figure 5 shows the external shape of the sample. The samples are step-shaped molded products whose thickness varies in steps of 1 mm from 1 mm to 10 mm, and each sample has a different combination of PET origin and cooling method. Then, the thickness at which PET crystallized in each sample was investigated.

Table 1 below shows the PET crystallization conditions for each sample.

As shown in Table 1, the thickness of crystallization varies depending on the origin of PET and the cooling method. In sample 1 using virgin PET, there is no region where PET is crystallized at a thickness of 1 to 10 mm, and a thickness greater than at least 10 mm is required in order to crystallize virgin PET by rapid cooling. . In sample 2, in which virgin PET was used and the cooling method was slow cooling, although a crystallized region was observed at a thickness of 7 mm, complete crystallization did not occur even at a thickness of 10 mm.

In Table 1, sample 3, which was formed using recycled PET and molded by rapid cooling, is described as having a crystallization thickness of 3 mm to 4 mm, which is not the case in the step-shaped molded product where the thickness is 3 mm. It is shown that a part of the film was crystallized and the entire region was crystallized in a region with a thickness of 4 mm. Similarly, for Samples 4 to 6, the thickness when a part of the region is crystallized and the thickness when the entire region is crystallized are shown in numerical ranges in the stepped samples. FIG. 6 shows photographs of prepared samples 1 to 6. In FIG. 6, the crystallized region in each sample is indicated by a white line frame. Note that the x and y directions shown in FIG. 6 are the same as the x and y directions shown in FIG.

As shown in Table 1 and FIG. 6, for the same type of PET, crystallization was easier when the cooling method was slow cooling than rapid cooling. This is probably because the cooling method using slow cooling resulted in a longer period of time in which the PET remained in the crystallization temperature range than the rapid cooling method.

Regarding the types of PET, it was found that recycled PET and biomass PET crystallize more easily than virgin PET. A possible reason why recycled PET is more likely to crystallize than virgin PET is that recycled PET retains a thermal history from when it was molded into a molded product in the past. One hypothesis is that since the crystallization of a substance is the regular arrangement of the molecules that make up the substance, recycled PET can be cooled from a high-temperature molten state even if it has not crystallized in the past. By the time it becomes a molded product, it has been exposed to crystallizing temperatures at least once. That is, recycled PET has in the past transitioned from a molten state in which the molecular arrangement was random to a state in which the molecular arrangement was regular. Therefore, compared to virgin PET, it can be considered that the molecular arrangement of recycled PET changes so that it is more easily crystallized during the process of being cooled from a molten state.

In any case, it has been confirmed that, in fact, virgin PET needs to be thicker than recycled PET or biomass PET in order to crystallize it. According to the method for manufacturing a resin container according to the first embodiment, by utilizing the difficulty of crystallization depending on the type of PET described above, the container has a wall thickness specified as a product specification. However, by appropriately selecting the type of PET and the cooling method, any region can be formed of crystalline PET.

===Second embodiment===
<Container manufacturing procedure>

The method for manufacturing the container according to the second example is the "injection blow method" and the "cold parison method" similarly to the first example. However, the procedure for crystallizing PET is different from the first embodiment. FIG. 7 shows the steps of the manufacturing method according to the second embodiment. In the method for manufacturing a container according to the second embodiment, as in the first embodiment, a resin material containing PMMA is first used as the main raw material, and this resin material is subjected to an injection process (s11) and a subsequent cooling process. (s12) to produce a preform. In addition, in the second example, based on the results in Table 1, etc., the type of PET (for example, recycled PET) and the thickness of the preform (for example, 3mm ), and the cooling method (eg, quenching) is selected.

In the second example, by heating the molded preform again, a part of the PET constituting the preform is crystallized (s13), and then the stretch blow molding process (s15) is performed. A container is produced through a heating step (s14) and a blow molding step (s15). In the blow molding step (s15), similarly to the first embodiment, areas in the preform where PET is not crystallized are transformed into a pearl-like texture. In this way, in the second embodiment, a part of the preform is transformed into crystalline PET by the reheating step (s13) performed prior to the heating step (s14) for the stretch blowing step (s15). There is.

Note that in the reheating step (s13), a region of the preform to be crystallized is heated at a higher temperature than other regions. Note that when the body 5 is provided with an annular pearl-like region 11 and a region 12 made of crystalline PET, as in the container 1b shown in FIG. 1B, for example, in the preform, the container 1b is later A predetermined annular region may be heated at a predetermined temperature for a predetermined period of time by using an annular heater or the like in the region that will become the body portion 5 . When virgin PET is used as the PET, heating is performed for 40 seconds or more so that the temperature of the heated portion becomes 195°C.

As described above, the container manufactured by the manufacturing method according to the second example, like the container manufactured by the method of the first example, has a region having a pearl-like texture and a region made of crystalline PET. It has a novel texture that is a mixture of However, unlike the first embodiment, there is no need to increase the thickness of the region to be crystallized in the preform, so there is no need to separately prepare a mold for the preform. Therefore, the cost for the mold can be reduced. Furthermore, by appropriately changing the area to be heated, it is possible to freely form areas made of crystalline PET in different positions even in containers originating from the same preform, allowing for complex designs such as designs and letters to be formed. Decorations with contours can also be made of crystalline PET.

<PET crystallization conditions>
Similarly to the first example, in the container manufacturing method according to the second example, it is possible to manufacture containers using different types of PET. Therefore, the relationship between reheating conditions and PET crystallization was investigated. Here, a plurality of preforms having a uniform wall thickness of 3 mm were produced using two types of resin materials: a resin material containing only virgin PET and a resin material containing virgin PET and recycled PET at a mass ratio of 1:1. Next, a predetermined region on the surface of each preform was set as a heating region, and the heating region was heated by changing the output and heating time of the heater used in the reheating step (s13). Then, the surface temperature of the heated region after the elapse of the heating time was measured, and the presence or absence of crystallization in the heated region was examined.

Table 2 below shows the relationship between reheating conditions and crystallization.

In Table 2, Samples 7 and 9 show the surface temperatures when PET crystallizes over almost the entire heating region when the heating time is 40 seconds and the output of the heater is varied. Samples 8 and 10 show the time taken for PET to crystallize over almost the entire heating region when the heater output and temperature are fixed. That is, the crystallization conditions for each sample are essential conditions for crystallization. For example, the crystallization conditions for sample 7 indicate that a preform with a thickness of 3 mm is heated using virgin PET until the surface temperature reaches 195° C. in 40 seconds.

From the results shown in Table 2, it was found that the resin material containing recycled PET crystallized at a lower temperature or in a shorter time than the resin material containing only virgin PET. Note that even if a resin material or biomass PET is used in which the mass ratio of virgin PET to recycled PET is different from 1:1, the heating time required for crystallization and the By examining the surface temperature of the preform, reheating conditions for crystallization can be determined.

===Third Example===
In the manufacturing method according to the third example, the container 1c shown in FIG. 1C can be manufactured. As described above, the container 1c shown in FIG. 1C has a two-layer structure consisting of an outer layer 8 having a pearl-like texture and an inner layer 7 made of crystalline PET. In the method for manufacturing a container according to the third embodiment, a layer having pearl-like regions 11 is formed using a resin raw material obtained by adding PMMA to PET, and a layer having regions 12 made of crystalline PET is formed using a resin raw material in which PMMA is added to PET. is formed using PET.

FIG. 8 shows a procedure for manufacturing a container by the manufacturing method according to the third example. FIG. 8 shows a procedure for manufacturing a container 1c shown in FIG. 1c, which has an outer layer 8 having a pearl-like region 11 and an inner layer 7 having a region 12 made of crystalline PET. FIG. 9 shows a longitudinal cross-sectional view of the preform 40 that is the origin of the container 1c. Below, with reference to FIGS. 8 and 9, the procedure of the method for manufacturing a container according to the third embodiment will be described.

In the method for manufacturing a container according to the third embodiment, first, a preform 41 is injection molded under conditions that do not crystallize PET (s21). For example, a preform 41 made of recycled PET and having a thickness of 3 mm is produced by injection of molten resin and subsequent rapid cooling.

Next, a preform made of recycled PET (hereinafter sometimes referred to as "inner preform 41") is used as an inner mold, and a main body part (hereinafter sometimes referred to as "inner body part 42") is formed. A portion that will later become the outer layer body 8 (hereinafter sometimes referred to as "outer body portion 43") is formed on the outer surface by injection molding (s22). At this time, a resin material containing PET and PMMA in a predetermined mass ratio (for example, recycled PET:PMMA=99:1) is used. Then, this resin material is injection molded, and an outer main body part 43 having a predetermined thickness (for example, 0.5 mm) is laminated on the inner main body part 42 of the inner preform 41 to produce a two-layered preform 40. . Note that the inner main body portion 42 of the inner preform 41 is reheated and crystallized by the heat generated when the outer main body portion 43 is injection molded.

Next, the two-layer preform 40 is stretch-blow molded in the same manner as in the first and second embodiments. That is, after heating the two-layered preform 40 to a temperature necessary for stretch blow molding, the preform 40 is stretch blow molded (s23, s24). As a result, a container 1c shown in FIG. 1C is produced, in which an outer layer 8 whose body 5 has a pearl-like texture and an inner layer 7 made of crystalline PET are laminated.

Note that the inner preform 41 can be crystallized before forming the outer main body part 43 by changing the thickness and the type of PET used as the raw material. In addition, when it is desired to configure a part of the inner layer body 7 with crystalline PET, for example, a part of the inner preform 41 is crystallized based on the crystallization conditions shown in Table 1 or Table 2. By controlling the contact time between the molten resin and the inner main body 42 when molding the outer main body 43, the uncrystallized region of the inner layer 7 can be crystallized by the heat generated when the outer main body 43 is molded. You can also prevent it from happening. Of course, based on the PET crystallization conditions shown in Tables 1 and 2, the pearl-like inner layer body 7 is molded using a resin material made of PET and PMMA, and the pearl-like region 11 is not crystallized. Alternatively, only the outer layer 8 may be made of crystalline PET.

In this way, according to the manufacturing method according to the third example, it is possible to manufacture a container with different textures in the thickness direction.

===Amount of acrylic resin added===
In the method for manufacturing a container according to an embodiment, a preform injection-molded using a resin material in which an acrylic resin is added to PET is stretch-blow-molded, thereby forming a region made of crystalline PET obtained at the preform stage. While keeping it intact, other areas have been transformed into a pearlescent color. The acrylic resin functions as an additive for changing the quality of the resin material into a pearly appearance, and the greater the amount of the acrylic resin added, the more easily the resin material changes into a pearly appearance. However, on the other hand, if the pearlescent texture becomes too dominant due to stretch blow molding, it may become difficult to distinguish the crystalline PET region formed at the preform stage in the completed container. Therefore, we investigated the numerical range of the mass ratio of PET and acrylic resin that allows the crystalline PET region and the pearl-like region to coexist.

Here, a container made of resin materials with different mass ratios of PET and PMMA is manufactured by the container manufacturing method according to the second embodiment, and PET and acrylic resin are used as the resin materials when molding the container. The mass ratios of PET:PMMA were 99:1, 97.5:2.5, and 90:10. Note that the preform includes recycled PET or virgin PET as PET, and the wall thickness is adjusted in the same manner as the preform manufacturing step (s11) in the manufacturing method according to the second embodiment shown in FIG. It was manufactured so that the diameter was 3 mm. Next, the preform was heated for 40 seconds at a surface temperature of 195° C. to form a region made of crystalline PET, and then a container was produced by stretch blow molding.

When containers were manufactured using the procedure shown in Figure 7 using resin materials with different mass ratios of PET and PMMA, the pearl tone was dominant in the container using resin materials with a PET:PMMA ratio of 90:10. Although the texture was slight, it was more difficult to discern the crystallized region than in containers made of other resin materials. Note that if the ratio of PET is lowered, the characteristics of PET, which is characterized by high strength, will be lowered, so naturally the strength of the container will also be lowered. Therefore, the mass ratio of PET and PMMA may be appropriately set in consideration of aesthetic appearance, strength, and the like. Realistically, when the total mass of PET and PMMA is 100, the mass of PET may be 90 or more and 99 or less.

===Other Examples===
As an application example of the method for manufacturing a resin container according to the first or second embodiment, for example, by using only a resin material made of PET, a container in which a transparent region and a crystalline PET region coexist can be manufactured. It can be made.

Although the acrylic resin used in the above examples is a virgin material, a recycled material (for example, Reapet N: manufactured by Midorikawa Kasei Kogyo Co., Ltd.) may also be used for the acrylic resin. By using recycled materials for both PET and acrylic resin, it is possible to reduce the environmental impact of the container manufacturing process, moving towards a decarbonized society. Note that the acrylic resin is added to PET to obtain a pearl-like texture, and the pearl-like texture is not caused by molecular arrangement, unlike crystalline PET. In actual preliminary studies, it was found that there was no difference in pearlescent texture between virgin material and recycled material if the addition ratio to PET and manufacturing procedure were the same.

The PET used in each of the above embodiments may contain at least one of virgin PET, recycled PET, and biomass PET. The acrylic resin may also contain at least one of virgin material and recycled material.

The container manufacturing methods according to the first and second embodiments may be combined. For example, if the first and second embodiments are combined, the PET in the region with a slope in the preform can be crystallized in stages according to the wall thickness, and any region can be reheated to increase the thickness. PET in regions of reduced thickness can be crystallized.

In the container manufacturing method according to the second embodiment shown in FIG. 7, the reheating step (s13) for crystallizing PET and the heating step (s14) before blow molding may be performed simultaneously. In this case, the reheating step (s13) can be omitted and the temperature in the heating step (s14) before blow molding can be set to a temperature at which PET crystallizes, so that the entire container body 3 can be formed from crystalline PET. Alternatively, a part of the container body 3 may be heated to a temperature at which PET crystallizes, and the other region may be heated at a temperature required for blow molding below the temperature at which PET crystallizes. In any case, the PET in the reheated region may be crystallized by reheating part or all of the preform at a temperature higher than the temperature at which PET crystallizes.

Two heating steps, a reheating step (s13) for crystallizing PET and a heating step (s14) for blow molding, may be performed continuously. In this case, since the crystallization of PET can be controlled by temperature, either of these two heating steps may be performed first.

FIGS. 1A to 1C show examples of containers (1a to 1c) manufactured by the manufacturing method according to the example, but it goes without saying that the containers according to the example can be manufactured by the stretch blow molding method. If so, the external shape may be any shape.

1a to 1c resin container, 2 neck of container, 3 main body of container, 4 bottom,
5 trunk, 6 inner layer, 7 outer layer, 11 pearlescent area,
12 region made of crystalline PET, 30, 40 preform,
32 neck of preform, 33 main body of preform,
34 cylindrical part of preform, 41 inner preform, 42 inner main body part,
43 outer main body part, 51 slope area

Claims (13)

A method for manufacturing a bottomed cylindrical resin container made of a resin material containing polyethylene terephthalate (hereinafter referred to as PET), the method comprising:
a preform production step of producing a preform by injection molding;
a crystallizing step of crystallizing the PET in at least some regions of the preform;
a blow molding step of molding the preform into a resin container by stretch blow molding,
In the preform production step, a resin material containing acrylic resin is used with the PET as the main raw material,
In the blow molding step, a region made of PET crystallized in the crystallization step and a pearl-like region that is white and more glossy than the region made of crystallized PET are mixed on the surface of the resin container. let,
A method for manufacturing a resin container characterized by the following. The PET includes one or more of petroleum-derived virgin PET, recycled PET, and biomass PET,
The acrylic resin includes either or both of petroleum-derived virgin acrylic and recycled acrylic,
2. The method for manufacturing a resin container according to claim 1. 2. The resin material according to claim 1, wherein the resin material includes polymethyl methacrylate resin in PET, and the mass percentage of the PET contained in the resin material is 90% or more and 99% or less. Method for manufacturing resin containers. In the preform manufacturing step, the preform having different thickness depending on the region is manufactured by injection molding, and the PET in the thick region is crystallized. A method for manufacturing a resin container according to any one of the above. A claim characterized in that, in the preform manufacturing step, the preform having a sloped wall thickness is manufactured by injection molding, so that the degree of crystallinity of the PET is changed in stages according to the wall thickness. Item 4. The method for producing a resin container according to item 4. 4. The method for manufacturing a resin container according to claim 1, wherein in the crystallization step, the produced preform is heated to crystallize the PET in the heated region. A method for manufacturing a bottomed cylindrical resin container made of a resin material containing polyethylene terephthalate (hereinafter referred to as PET), the method comprising:
a preform production step of producing a preform by a process including injection molding;
a blow molding step of molding the preform into a resin container by stretch blow molding,
In the preform manufacturing step,
A first step of molding a single-layer preform by injection molding a resin material containing acrylic resin using PET as the main raw material;
By injection molding a resin material made of PET on the inner or outer side of the preform, an inner layer or an outer layer made of PET is laminated on the preform produced in the first step to form a two-layer structure. performing a second step of molding the preform;
In the blow molding step, a region made of crystallized PET is formed in a region corresponding to the single-layer preform, and a region made of crystallized PET is formed in white in a region corresponding to the inner layer or outer layer laminated in the second step. forming a pearl-like area that is more lustrous than the area made of molten PET,
A method for manufacturing a resin container characterized by the following. A method for manufacturing a bottomed cylindrical resin container made of a resin material containing polyethylene terephthalate (hereinafter referred to as PET), the method comprising:
a preform production step of producing a preform by a process including injection molding;
a blow molding step of molding the preform into a resin container by stretch blow molding,
In the preform manufacturing step,
A first step of molding a single layer preform by injection molding a resin material made of PET;
By injection molding a resin material containing acrylic resin using PET as the main raw material, an inner layer or an outer layer made of PET is added to the preform produced in the first step on the inner or outer surface of the preform. a second step of laminating and forming a two-layer preform;
In the blow molding step, a region made of crystallized PET is formed in a region corresponding to the inner layer or the outer layer, and a white region made of the crystallized PET is formed in a region corresponding to the single layer preform. forming a pearl-like area with more luster than the other areas,
A method for manufacturing a resin container characterized by the following. The PET includes one or more of petroleum-derived virgin PET, recycled PET, and biomass PET,
The acrylic resin includes either or both of petroleum-derived virgin acrylic and recycled acrylic,
9. The method for manufacturing a resin container according to claim 7 or 8. The resin material for injection molding the preform having the region formed of the crystallized PET contains polymethyl methacrylate resin in PET, and the mass proportion of the PET contained in the resin material is: The method for manufacturing a resin container according to claim 7 or 8, wherein the resin container is 90% or more and 99% or less. A resin container having an opening at the tip,
Contains acrylic resin with polyethylene terephthalate (hereinafter referred to as PET) as the main component,
A mixture of crystallized PET and a white region that is glossier than the region made of the crystallized PET,
The region where the crystallized PET exists is formed thicker than other regions;
A resin container characterized by: A region having a gradient in wall thickness is formed, and in the region having a gradient in wall thickness, the degree of crystallinity of the PET gradually increases as the wall thickness increases. Item 12. The resin container according to item 11. A resin container having an opening at the tip,
It has a two-layer structure in which a first layer made of polyethylene terephthalate (hereinafter referred to as PET) and a second layer containing PET as a main component and an acrylic resin are laminated in the thickness direction,
The first layer has a region made of crystallized PET,
The second layer is white and formed into a pearl-like shape that is more glossy than the region made of crystallized PET.
A resin container characterized by:

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