JPH0538748A - Base cup and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a lightweight and thin-walled polyester base cup excellent in strength and manufacturing method thereof. CONSTITUTION:The subject base cup is produced by biaxial stretch blow molding a bottomed cylindrical polyester parison so as to form an intermediate formed body 2 consisting of a mouth part 21, a conical shoulder part 22, a cylindrical barrel part 23 and a bottom part 24 having a pounding part 23 in the order named and finally cutting off the mouth part side at the upper end part C of the barrel part 23 of the intermediate formed body 2 in order to obtain the subject base cup.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a base cup for a plastic bottle and a method for producing the same, and more particularly to a base cup made of polyester resin which is lightweight, thin and has excellent strength, and a method for producing the same.

[0002]

BACKGROUND OF THE INVENTION Biaxially stretched blow-molded bottles made of saturated polyester resin represented by polyethylene terephthalate have excellent transparency and surface gloss, and are beautiful and have a gas barrier. Excellent in water resistance, water impermeability, content resistance and storage stability. In addition, there are many advantages such as low heat generation during combustion, which does not damage the furnace and is easily disposable.
Therefore, it is widely used in various drinking water, seasonings, containers (bottles) for foods such as alcoholic beverages, and the like.

Among such biaxially stretch blow-molded bottles, there is one in which a so-called base cup is attached to the bottom. The base cup adds self-reliance to the bottle,
Also, in some cases it is installed to reinforce the bottom part,
This is often used, for example, for bottles whose contents have a high internal pressure, such as carbonated drinks. This is because, in such a bottle, it is common to mold the bottom of the bottle into a rounded convex shape in order to improve the internal pressure resistance.

The base cup used in a conventional bottle is mainly a polyethylene resin injection-molded. A bottle having such a base cup mounted on a bottle body made of a polyester resin such as polyethylene terephthalate is a bottle. Commonly used.

By the way, in recent years, recycling of plastic bottles has been considered from the viewpoints of resource saving and waste disposal. For example, recycling is considered in which a used bottle is crushed and a new plastic bottle is manufactured using the crushed plastic material. However, the conventional bottle with a base cup is inferior in recyclability because the bottle body and the base cup are made of different kinds of plastics as described above.
That is, in order to recycle, the bottle body and the base cup must be separated.

Further, the conventional base cup formed by injection molding of polyethylene resin has a heavy defect of 14 to 16 g for a plastic bottle for 1.5 liters, for example.

In order to improve recyclability, it is possible to form the base cup from the same resin as the bottle body, that is, a polyester resin such as polyethylene terephthalate. However, it is attempted to injection-mold polyester to produce the base cup. Then, the resin may be oriented in the flow direction of the resin at the time of injection molding, and cracks may occur along the oriented direction. Normally, when injection molding a base cup-shaped article, the center of the bottom of the base cup (bottom pole)
Although an injection gate is provided at a position corresponding to, since the resin flows radially from the injection gate in the molding die, the base cup is easily cracked radially. In addition, the drop strength often decreases even if cracks do not occur. Furthermore, in injection molding of polyester resin, there is a limit to the thinning of the base cup, and thinning and weight reduction cannot be achieved.

On the other hand, when a base cup is manufactured by a thermoforming method of pressure forming or vacuum forming using a polyester resin sheet, sufficient stretching cannot be obtained (particularly in the circumferential direction near the open end of the base cup). Of which is poor), and a base cup having good strength cannot be obtained. In addition, the thickness of the heel portion (corner portion of the bottom portion of the base cup) from the side surface of the base cup to the ground contact portion is not sufficient.

In particular, when recycling plastic bottles (and base cups) in consideration of resource saving and environmental problems (problems of disposal) (that is, recycling used bottles to form base cups). When used as a raw material), it becomes more difficult to obtain a good base cup by the conventional injection molding method or thermoforming method. This is because once the polyester resin has undergone a molding step involving heating and melting, the degree of polymerization is lowered by hydrolysis or thermal decomposition and the intrinsic viscosity (IV value) is lowered. The degree of the decrease in the intrinsic viscosity largely depends on the water content of the resin, the high temperature heat history, etc., but usually decreases by 3 to 8%. Therefore, when injection molding is performed using a recycled polyester resin, the strength of the molded product obtained by the decrease of the resin viscosity becomes more remarkable. Further, cracks are more likely to occur along the resin flow direction (the resin flow direction at the time of injection).

On the other hand, in the thermoforming method,
The amount of resin to be recycled (recycled) to the raw material (the part that becomes a non-product by one thermoforming) is 30-
Since it reaches 50%, the intrinsic viscosity of the recycled resin is remarkably lowered, and a molded product (base cup) having good strength cannot be obtained, and the moldability is deteriorated. Therefore, it is necessary to add a large amount of new polyester resin to the recycled resin to ensure moldability, but even if this is done, the problem of strength as described above remains.

Accordingly, an object of the present invention is to provide a base cup made of polyester which is thin and lightweight and has excellent strength, and a method for producing the same, and in particular, a base cup using recycled polyester resin and recycled polyester. It is an object of the present invention to provide a method capable of producing a base cup having good strength even when a resin is used.

[0012]

As a result of earnest research to solve the above-mentioned problems, the present inventor has found that a bottomed cylindrical parison made of polyester resin is biaxially stretch blow-molded to first produce an intermediate molded body. However, it was discovered that by cutting the mouth side of this intermediate molded body and using the lower portion as a base cup, it is possible to obtain a polyester resin base cup that is thin and has excellent strength due to the effect of biaxial stretching. In particular, in the production thereof, it was discovered that the cut upper part of the intermediate molded body can be recycled and used as a resin for parison molding, and the present invention has been completed.

That is, the base cup of the present invention is characterized in that the mouth side of an intermediate molded body formed by biaxially stretch blow molding a bottomed cylindrical parison made of polyester resin is cut off.

Further, the method of the present invention for producing a base cup for a bottle comprises: (a) heating a bottomed cylindrical parison made of a polyester resin to a stretching suitable temperature, and (b) biaxially stretching the parison. Molded, to produce an intermediate molded body consisting of a mouth portion, a conical shoulder portion continuous to the mouth portion, a cylindrical body portion, and a bottom portion having an annular grounding portion, (c) It is characterized in that the cylindrical body of the intermediate molded body is cut at the upper end thereof perpendicularly to the axis, and the lower portion of the cut intermediate molded body is used as a base cup.

[0015]

The present invention will be described in detail below.

FIG. 1 is a sectional view showing an example of a parison that can be used in the method of the present invention. The parison 1 has a mouth portion 11 having a support ring 18, a body portion 12, and a bottom portion 13.

The mouth portion 11 of the parison 1 is a portion that serves as a grip portion in the biaxial stretch blow molding described later, and is not substantially deformed in the biaxial stretch blow molding. In addition, two support rings 1 are provided at the mouth portion 11 of the parison 1 shown in FIG.
However, the present invention is not limited to this.

The body 12 has a substantially cylindrical shape,
The upper portion 12a is formed so as to become thinner toward the mouth portion 11. The upper portion 12a of the body portion 12 is a portion that serves as a conical shoulder portion of an intermediate molded body described later. By forming the upper portion 12a of the body 12 thin in advance in this manner, the conical shoulder portion of the intermediate compact can be easily thinned. Also, the lower portion 12 of the body portion 12
The b is formed to be thicker than the upper portion 12a, and has a cylindrical shape having substantially the same thickness. The lower portion 12b is a portion that is sufficiently stretched in the biaxial stretch blow molding and forms the grounding portion of the cylindrical body portion and the bottom portion of the intermediate molded body.

The bottom 13 of the parison 1 is the body 1 described above.
It is formed somewhat thinner than the lower part 12b of 2 and has a smooth convex curved surface shape. The bottom portion 13 is a portion corresponding to the central portion of the bottom portion of the intermediate molded body that is formed by the biaxial stretch blow molding, and is a portion that is pushed by the stretch rod in the biaxial stretch blow molding. If the bottom portion 13 is formed to be somewhat thinner than the lower portion 12b of the body portion 12, the bottom portion 13 can be easily cooled (temperature adjustment) to a temperature lower than that of the body portion 12 in the hot parison molding method. This is because the thinner resin layer is cooled more quickly. Therefore, even if the bottom portion 13 is pushed by the stretching rod during stretching, the stretching rod can stretch the body portion 12 without breaking through the bottom portion 13.

The parison 1 shown in FIG. 1 can be manufactured by a known injection molding using a molding die having a cavity having a shape corresponding thereto.

A polyester resin is used as the resin forming the parison 1. As the polyester resin, a thermoplastic resin composed of saturated dicarboxylic acid and saturated dihydric alcohol can be used. Saturated dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, naphthalene-1,4- or 2,6-dicarboxylic acid, diphenyl ether-4,4'-dicarboxylic acid, diphenyldicarboxylic acids, diphenoxyethanediethanedicarboxylic acids Aromatic dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid, decane-
Aliphatic dicarboxylic acids such as 1,10-dicarboxylic acid and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid can be used. As the saturated dihydric alcohol, aliphatic glycols such as ethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, diethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, hexamethylene glycol, dodecamethylene glycol and neopentyl glycol are used. Glycols, cycloaliphatic glycols such as cyclohexanedimethanol, 2,2-bis (4 '
-β-hydroxyethoxyphenyl) propane, other aromatic diols and the like can be used. A preferred polyester is polyethylene terephthalate composed of terephthalic acid and ethylene glycol, and is appropriately selected in consideration of the material of the bottle main body part on which the base cup is mounted.

As the polyester resin, a novel one prepared from the above-mentioned components can be used. However, in the present invention, not only that, but also a resin which has undergone a molding step involving heating and melting once, for example, once into a bottle. A molded product, or a non-product part (which will be described later in detail) cut out from the intermediate molded product obtained during the process of the method of the present invention can be recycled and used.

The polyester resin to be recycled (which has been already molded by heating and melting) is once crushed to remove fine powder, preferably crystallized, and then sufficiently dried to be used as a resin for injection molding. Can be used.
Incidentally, in the method of the present invention, the parison as described above may be molded only from recycled polyester resin,
If necessary, a recycled polyester resin and a new polyester resin may be mixed and used.

The polyester resin used for injection molding of the parison has an intrinsic viscosity of 0.7 to 0.8 in the case of a new resin.
The degree is good, but it is not limited to this as long as the injection molding is well performed. Further, in the case of recycled polyester resin (or a mixture of this and a new polyester resin), the intrinsic viscosity is lower than that of the novel polyester resin as described above, but in the present invention, the parison is formed by injection molding. Since it is produced, recycled polyester resin having an intrinsic viscosity of 0.65 or less can be preferably used. When using recycled polyester resin, the intrinsic viscosity is preferably 0.5.
The thing of about 0.7 is used.

In the polyester resin, additives such as stabilizers, pigments, antioxidants, heat deterioration preventing agents, UV deterioration preventing agents, antistatic agents, antibacterial agents, etc. may be used in the range not impairing the object of the present invention. An appropriate amount of resin can be added.

Once the parison of the shape shown in FIG. 1 has been obtained by injection molding, the parison 1 is then heat-conditioned to a temperature suitable for biaxial stretch blow molding. First, the biaxially stretched blow molding does not substantially deform, and the mouth portion 11 serving as a gripping portion is basically not heated. Actually, it is maintained at 20 to 50 ° C.
Moreover, since the body portion 12 is a portion that is largely stretched,
Keep at a high temperature of 0 to 120 ° C. If necessary,
The thin upper portion 12a and the thick lower portion 12b of the body 12 are kept at different temperatures. The thin upper portion 12a is 100 to 12
The temperature is preferably 0 ° C, and the thick lower portion 12b has a thickness of 90-11.
It is better to set it to 0 ° C. Further, it is preferable that the bottom portion 13 has a lower temperature as described above, specifically, 60 to 90 ° C.
And

The heating and temperature control of the parison can be carried out by using a known method and apparatus.

After holding each part of the parison 1 at the above-mentioned temperature, biaxial stretch blow molding is carried out by a known method.
An intermediate molded body having the shape shown in is obtained. The intermediate molded body 2 has a mouth portion 2.
1, a conical shoulder 22 that is continuous with the mouth 21 and has a large diameter downward, and a body 2 formed into a substantially cylindrical shape.
3 and a bottom portion 24 having an annular grounding portion 25.

First, as described above, the mouth portion 21 of the intermediate molded body 2 has substantially the same shape as the mouth portion 11 of the parison 1 shown in FIG.

Next, the cone-shaped shoulder portion 22 has a large diameter downward, and the mouth portion 21 and the cylindrical body portion 23 are continuous with each other. The diameter of the cone-shaped shoulder portion 22 is changed to the intermediate molded body 2
It is preferable that the angle (θ in FIG. 2) formed by the plane P perpendicular to the axis of and the conical surface 22a of the shoulder be 5 ° or less. Further, it is preferable that the conical shoulder portion 22 is formed thinly,
Specifically, the thickness is preferably 0.2 mm or less. The conical shoulder 22 has such a diameter-expanded state and thickness.
Molding reduces the portion to be cut off (non-product portion that does not become the base cup). Specifically, the weight of the portion to be cut off is 20% by weight or less of the entire intermediate molded body 2, and the amount of resin to be recycled is reduced, which is preferable. The draw ratio of the conical shoulder 22 is preferably about 8 to 15.

The body portion 23 is formed into a substantially cylindrical shape and is largely stretched. The draw ratio of the body 23 is 3 to
It is preferable that the stretching ratio is about 15, preferably about 6 to 13, and even if the stretching ratio is set to about this value, it is usually 0.2
Large mechanical strength and heat resistance can be imparted.

The bottom portion 24 is composed of an annular grounding portion 25, a bottom pole portion 26 formed thickly in the central portion, and a smooth curved surface portion 27 that connects the annular grounding portion 25 and the bottom pole portion 26. .. In the present embodiment, the annular grounding portion 25 is formed in the shape of a partial torus surface, but the present invention is not limited to this and may be an annular grounding portion having a desired cross-sectional shape. In addition,
The partial torus surface referred to here is a curved surface portion obtained when a substantially donut-shaped object is cut in half along its ring. ) 28 is illustrated.

The bottom pole portion 26 formed at the center of the bottom portion is a portion usually called a navel, and is the bottom portion 13 of the parison 1 in FIG.
It is a part derived from. As described above, this portion is a portion that is pushed by the stretching rod in the biaxial stretch blow molding, and is held at a relatively low temperature so that it becomes thicker and is hardly stretched or undergoes a low stretch of about 3 times or less. On the other hand, the grounded portion 25 having a partial torus surface shape is relatively greatly stretched (stretching ratio is about 8 to 12), and even if it is not formed to be so thick, a large mechanical strength is imparted by the effect of stretching. Further, the curved surface portion 27, which connects the grounded portion 25 and the bottom pole portion 26, which are in the shape of a partial torus, is also stretched relatively large, and good mechanical strength is imparted. The draw ratio of the curved surface portion 27 is preferably about 6 to 10.

When the above-mentioned intermediate molded body 2 is obtained by the biaxial stretch blow molding, it is heat-treated (heat set) in a stretch blow molding die or the like if necessary, and released.

Next, the body 2 of the intermediate molded body 2 is cut with a cutter or the like.
Cut the entire circumference at the upper part of 3 (site C shown in FIG. 2). The cut lower part becomes the base cup.

FIG. 3 is a cross-sectional view showing the base cup 3 obtained by the above method. The base cup 3 is schematically attached to a bottle 4 having a hemispherical shape or a rounded bottom portion similar thereto. It is shown in the figure.

The upper end portion of the cylindrical side surface portion 23a of the base cup 3 is in contact with the lower portion of the body portion of the bottle 4 so as to be firmly tightened in the radial direction from the outside.
The bottom portion of the base cup 3 substantially abuts the curved surface portion 27 of the bottom portion 24 of the base cup 3. In addition, bottle 4 of base cup 3
The adhesion to the surface can be performed by welding with ultrasonic waves or adhesion using an adhesive made of polyester resin.

Although the present invention has been described in detail with reference to the accompanying drawings, the present invention is not limited to this and various modifications can be made without departing from the spirit of the present invention. For example, the shape of the ground contact portion 25 is not limited to the partial torus surface shape,
It may be changed appropriately.

[0039]

As described in detail above, since the base cup of the present invention is formed by biaxially stretch blow molding a polyester resin parison, it has a large mechanical strength due to the stretching effect even if it is thin. Further, since the base cup is made of the same material as the polyester bottle currently widely distributed, the recyclability of the used bottle equipped with the base cup is improved.

Further, in the method of the present invention, since recycled polyester resin having a low intrinsic viscosity can be used, resource saving can be achieved. In particular, only recycled polyester resin can be used, and the cut-off portion of the intermediate molded body that is not a product can also be used, so that manufacturing can be performed without waste.

Further, since each part including the grounding part can be easily made to have a desired thickness, a base cup faithful to the design can be obtained as compared with the thermoforming method.

The base cup of the present invention can be suitably used for polyester bottles such as carbonated drinks and various foods and drinks.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a parison that can be used in the method of the present invention.

FIG. 2 is a cross-sectional view showing an example of an intermediate molded body obtained by biaxially stretch blow molding the parison of FIG.

FIG. 3 is a cross-sectional view showing an example of a base cup obtained by cutting the intermediate molded body shown in FIG. 2, and schematically shows a state of being mounted on a bottle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 parison 2 intermediate compact 3 base cup 4 bottle 11 parison mouth 12 parison body 13 parison bottom 18 support ring 21 intermediate compact mouth 22 conical shoulder 23 intermediate compact body 23a base cup side 24 bottom 25 Grounding Part 26 Bottom Pole Part 27 Curved Part

Claims (9)

[Claims] 1. A base cup, which is obtained by cutting the mouth side of an intermediate molded body obtained by biaxially stretch-blow molding a cylindrical parison made of polyester resin. 2. The base cup according to claim 1, wherein the intermediate molded body has a mouth portion having substantially the same shape as the mouth portion of the parison, a conical shoulder portion, and a cylindrical body portion. When,
The bottom portion having a ground portion is continuously formed in that order, and is biaxially stretched 3 to 15 times except for the bottom pole portion formed in the central portion of the bottom surface of the mouth portion and the bottom portion. A base cup characterized in that the mouth side is cut off at the upper end of the body. 3. The base cup according to claim 1, wherein a bottom portion of the intermediate molded body has a partial torus surface portion that serves as a grounding portion, and a bottom pole portion that is located at a central portion of a bottom surface of the bottom portion. A base cup comprising a curved surface portion that connects the partial torus surface portion and the bottom pole portion, and the bottom pole portion is unstretched or low stretched by 3 times or less. 4. The base cup according to claim 1, wherein the polyester resin forming the parison is recycled polyester resin or a mixture of recycled polyester resin and novel polyester resin. The base cup, wherein the polyester resin forming the parison has an intrinsic viscosity of 0.65 or less. 5. A method for producing a base cup for a bottle, comprising: (a) heating a bottomed cylindrical parison made of a polyester resin to a temperature suitable for stretching, and (b) biaxially stretching blow molding the parison. Then, with the mouth,
A conical shoulder portion continuous with the mouth portion, a cylindrical body portion,
Producing an intermediate molded body consisting of a bottom having an annular grounding portion, (c) cutting perpendicularly to the axis at the upper end of the cylindrical body of the intermediate molded body, so that the cut intermediate molded body A method of manufacturing a base cup, characterized in that the lower portion is used as the base cup. 6. The method for manufacturing a base cup according to claim 5, wherein a portion other than a bottom pole portion formed in the mouth portion of the intermediate molded body and the bottom center portion of the bottom portion is doubled 3 to 15 times. A method for manufacturing a base cup, which comprises axially stretching. 7. The method of manufacturing a base cup according to claim 5, wherein the bottom portion of the intermediate molded body is a partial torus surface portion that serves as a grounding portion, and a bottom electrode that is located at the center of the bottom surface of the bottom portion. Part, and a curved surface part that connects the partial torus surface-like part and the bottom pole part, and the bottom pole part is unstretched or has a low stretch of 3 times or less. .. 8. The method of manufacturing a base cup according to claim 5, wherein the conical shoulder portion of the intermediate molded body is biaxially stretch blow molded to be thinner than other portions, and the axial line is formed. The method for manufacturing a base cup is characterized in that it has a conical surface shape that greatly expands with respect to the above, and the upper portion of the intermediate molded body to be cut out is 20% by weight or less of the entire intermediate molded body. 9. The method for manufacturing a base cup according to claim 5, wherein an upper portion of the cut intermediate molded body is crushed, and the crushed polyester resin is re-molded into the parison. A method for manufacturing a base cup, which is characterized by being used.