JP2002248675A - Multilayer preform and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer preform for molding a bottle not liable to bring about an interlayer release and having good impact resistance without bringing about blushing due to crystallization even by using a PCR resin and without gate or gate mark in a bottom. SOLUTION: The multilayer preform comprises an outer layer of a weight ratio (Y) represented by formula: Y=[(W-X)/W]×[To/(To+Ti)]×100(%), wherein W is a weight of the entirety of the preform, X is a weight of a neck part including a neck ring, To is a thickness of the outer layer of the preform and Ti is a thickness of an inner layer. A method for manufacturing the multilayer preform comprises the steps of supplying a molten resin lump A obtained by melt extruding a regenerated resin and cutting the resin in a predetermined amount into a female mold, then supplying a molten resin lump B obtained by melt extruding a virgin resin and cutting the resin in a predetermined amount on the lump A in the female mold, then press fitting a male mold in the female mold to form an outer layer 7 of the lump A, and compression molding so as to form the inner layer 6 of the lump B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer preform for molding a plurality of types of thermoplastic resins by compression molding and a method for producing the same. More specifically, the present invention relates to a predetermined amount of virgin resin and a predetermined amount of recycled resin. The present invention relates to a multilayer preform which is separately extruded and supplied into the same female mold, and compression-molded by a female mold and a male mold, and a method for producing the same.

[0002]

2. Description of the Related Art A PET bottle obtained by injection-molding a polyethylene terephthalate (PET) resin to form a preform, and biaxially stretch-blowing the preform, has a transparency, a gas barrier property, a mechanical strength and the like. It is widely used as a seasoning for liquid detergents, shampoos, cosmetics, soy sauce, sauces, etc., carbonated beverages such as beer, cola, cider, etc., fruit juices and beverage containers for mineral water.

[0003] In addition, the demand for PET bottles has recently increased and the problem of garbage disposal has arisen, and it is required to recycle post-consumer recycled (PCR) resins that have been used once and then recycled from the market. . PET
In order to collect and reuse used PET bottles for the purpose of resin recycling, the collected PET bottles are crushed, washed, dried and processed into flake-like resin, and this flake-like resin is placed in an outer layer or an intermediate layer. A multilayer preform or a multilayer bottle having a virgin resin as an inner layer is disclosed in JP-A-10-337770 and JP-A-11-77744.
It is proposed in Japanese Patent Publication No.

[0004] Multilayer preforms are generally manufactured by co-injection or multi-stage injection of different resins into a mold. The molding methods are roughly classified into a sequential co-injection molding method, a simultaneous co-injection molding method and a multi-stage injection molding method. Injection molding methods are known. In the sequential co-injection molding method, different resins are respectively supplied to a plurality of injection machines, a resin for forming inner and outer layers is first injected into a mold, and then a resin for an intermediate layer is injected to form a multilayer preform. Molding. In the simultaneous co-injection molding method, a resin for forming an inner layer and an outer layer is first injected into a mold, and a resin for forming an intermediate layer is injected in parallel with a slight delay to form a multilayer preform. Furthermore, in the multi-stage injection molding method,
First, a resin for forming an inner layer is injected into a mold to form a primary molded body, and then the primary molded body is transferred to another mold, and a resin for forming an outer layer is injected to form a multilayer preform. .

[0005] The shape of a multilayer preform manufactured by injection molding has a mouth-neck portion corresponding to the mouth-neck portion of a bottle and a bottomed cylindrical portion to be stretch-blow-molded. I have. Normally, a screw opening or the like, which is a means for engaging with the lid, is formed in the mouth and neck, and a gate or a trace of the gate when the resin is injected during injection molding is formed in the center of the bottom. Is always formed.

[0006]

In the conventional co-injection molding method or multi-stage injection molding method, when the content ratio of the PCR resin is increased, whitening and turbulence of the resin flow occur in the multilayer preform, especially near the bottom gate. However, bottles obtained by biaxially stretch-blowing the multilayer preform have poor appearance properties such as whitening of the bottom and craze, and have a problem of reduced impact resistance.

[0007] In particular, a regenerated resin such as a PCR resin has a higher thermal history than a virgin resin, and is easily crystallized due to the inclusion of some impurities. In co-injection molding, whitening occurs due to crystallization due to cooling efficiency, and in multi-stage injection molding, insufficient bonding strength occurs between layers. Therefore, the multilayer bottle obtained by biaxially stretch-blow-molding this multilayer preform has whitening due to crystallization, has poor appearance characteristics, and is liable to cause delamination and has a reduced impact resistance.

[0008] In order to solve the above problems, the present inventors first supply a PCR resin to an extruder, cut a fixed amount of the molten PCR resin extruded from the extruder, and place the cut resin in a female mold. And then supply the virgin resin to another extruder, cut a certain amount of the molten virgin resin extruded from this extruder and throw it on the molten PCR resin, then insert the male mold into the female mold. It has been found that by performing compression molding to form a multilayer preform, there is no occurrence of whitening due to crystallization, no disturbance of resin flow at the bottom, and good adhesion between layers. Furthermore, the multilayer bottle obtained by biaxially stretch-blowing the obtained multilayer preform also had no whitening due to crystallization, no craze occurred at the bottom, and good impact resistance.

That is, the present inventors supply a predetermined amount of a molten resin mass A made of a regenerated resin such as a PCR resin below the inside of a female mold, and a predetermined amount of a molten resin mass B made of a virgin resin thereabove. And the molten resin mass A and the molten resin mass B supplied into the female mold are compression-molded using the male mold and the neck mold, so that the transparency is reduced even if the ratio of the recycled resin is increased. No multilayer gate preform having no gate portion, no gate portion mark, and a mouth-neck portion and a neck ring portion made of only virgin resin was successfully obtained.

[0010] Accordingly, an object of the present invention is to provide a regenerated resin which has undergone a thermal history before a PCR resin or the like, without causing whitening due to crystallization and without a gate portion or a gate mark on the bottom. Provided is a multilayer preform for bottle molding, in which delamination hardly occurs and impact resistance is good. Furthermore, the recycling resin such as a PCR resin is reused more, that is, 25% by weight based on the total weight of the multilayer preform.
As described above, the present invention provides a method for producing a multilayer preform capable of recycling at least 30% by weight.

[0011]

According to the present invention, in a multilayer preform having an outer layer made of recycled resin and an inner layer made of virgin resin, the total weight of the multilayer preform is W, the mouth and neck including the neck ring, and the like. X, the thickness of the outer layer of the multilayer preform is To, and the thickness of the inner layer is Ti,
When the weight ratio of the outer layer is Y, the following formula is used: Y = [(W−X) / W] × [To / (To + Ti)] ×
A multilayer preform is provided, wherein the weight ratio (Y) of the outer layer represented by 100 (%) is 25 to 65%. Here, the weight ratio (Y) of the outer layer means the ratio of the weight of the outer layer resin to the total weight of the resin forming the multilayer preform.

Further, according to the present invention, there is provided a multilayer preform in which the outer layer tip ends under a neck ring below the mouth and neck, and the virgin resin is a polyester resin mainly composed of ethylene terephthalate, which is recycled. Provided is a multilayer preform in which a resin is a PCR resin composed of a polyester resin mainly composed of ethylene terephthalate, and a multilayer preform in which a gate portion or a trace of a gate portion does not exist at the bottom is provided.

Further, according to the present invention, a molten resin mass A obtained by melt-extruding a regenerated resin and cutting a predetermined amount is supplied into a female mold, and then a virgin resin is melt-extruded and cut to a predetermined amount. After supplying the molten resin mass B onto the molten resin mass A in the female mold, the male mold is pressed into the female mold to form the outer layer, and the molten resin mass B forms the inner layer. Thus, a method for producing a multilayer preform formed by compression molding is provided.

Further, according to the present invention, there is provided a method for producing a multilayer preform wherein the virgin resin is a polyester resin mainly composed of ethylene terephthalate and the regenerated resin is a PCR resin composed of a polyester resin mainly composed of ethylene terephthalate. , The total weight of the multilayer preform is W, the weight of the neck and neck including the neck ring is X, the thickness of the outer layer of the multilayer preform is To, and the thickness of the inner layer is T.
i, when the weight ratio of the outer layer is Y, the following formula: Y = [(W−X) / W] × [To / (To + Ti)] ×
A method is provided for producing a multilayer preform wherein the weight ratio (Y) of the outer layer, expressed as 100 (%), is 25-65%, the outer layer tip ending under the neck ring below the mouth and neck. A method for manufacturing a multilayer preform is provided, and a method for manufacturing a multilayer preform without a gate portion or a gate mark at the bottom is provided.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to FIGS. FIG. 1 shows a multilayer preform made according to the present invention. In FIG. 1, virgin resin and PCR
The multilayer preform 1 manufactured by compression molding of resin is
It is composed of a mouth and neck 2, a neck ring 3, a trunk 4 and a bottom 5. Further, the mouth and neck portion 2 and the neck ring 3 of the multilayer preform 1 are made of only virgin resin, and the other portions are made of an inner layer 6 of virgin resin and an outer layer 7 of recycled resin. In this specific example, the bottom 5 has a substantially hemispherical shape, but is not limited to this shape, and may have an elliptical shape or a flat bottom end. The bottom portion 5 of the multilayer preform 1 has no gate portion or gate mark on the bottom portion, the residual strain due to the flow orientation generated at the time of injection is reduced, and the multilayer preform 1 is substantially transparent when no coloring agent is added.

Next, FIGS. 2 and 3 show a process of supplying the molten resin to the female mold. As shown in FIG. 2, first, a recycled resin composition obtained by mixing a recycled resin alone or a virgin resin with a recycled resin is supplied to an extruder, and the recycled resin melt-extruded from a die head 11a is cut by a cutting unit 12a. The molten resin mass A is supplied into the female mold 13. Next, as shown in FIG. 3, a virgin resin is supplied to another extruder, and the virgin resin melt-extruded from the die head 11b is cut by a cutting means 12b to form a molten resin block B into a female mold 13.
Is supplied to the upper part of the molten resin mass A in the inside.

The molten resin lump A and the molten resin lump B are supplied into the female mold 13 by holding the cut molten resin lump A and the molten resin lump B by receiving means. The female mold 13 can be supplied into the female mold 13 by sequentially moving the female mold 13 below the die heads 11a and 11b.

FIGS. 4 and 5 show a step of compression-molding the molten resin mass supplied to the female mold using a female mold, a male mold and a neck mold. The molten resin mass A and the molten resin mass B filled in the female mold 13 are the female mold 13, the male mold 14 and the neck mold 1
5, the molten resin mass B first flows along the gap between the female mold 13 and the male mold 14, and subsequently, the molten resin mass A and the molten resin mass B The multilayered preform 1 is formed by flowing while flowing the molten resin mass B upward. Here, the female mold and the neck mold have been described as being separate bodies, but these can also be applied as an integrally molded body.

The multilayer preform 1 obtained by the compression molding has an inner layer 6 made of a virgin resin in the mouth and neck portion 2 and the neck ring 3 and an outer layer made of the virgin resin in the body portion 4 and the bottom portion 5. 7, the virgin resin is made of PET resin or a resin mainly composed of PET resin, and the recycled resin is made of PET resin or PE.
It is preferably a PCR resin mainly composed of a T resin or a resin composition thereof.

The gate portion existing in the multilayer preform manufactured by the conventional injection molding has various problems in terms of productivity, manufacturing cost, and characteristics of a final blow molded product. On the other hand, the multilayer preform manufactured according to the present invention has a mouth having a shape and dimensions corresponding to the mouth of a multilayer bottle as a final molded product, and a body and a bottom to be stretch blow-molded. Since there is no gate at the bottom, there is no need to cut the gate, and the center of the bottom is also smooth and uniform, and there is no decrease in transparency, no whitening due to crystallization, Is characterized in that no residual strain or wrinkles are caused by the flow orientation of the resin.

The multilayer preform is stretched at a temperature of 8
In a temperature range of 5 to 120 ° C., a multilayer bottle is manufactured by stretching in the longitudinal direction by a stretching rod and in the transverse direction by blow air by a stretch blow molding method known per se. The stretching ratio of the obtained multilayer bottle is preferably in the range of 1.2 to 6 times in the vertical direction and 1.2 to 4.5 times in the horizontal direction. For applications requiring heat resistance,
The heat setting can be performed by a means known per se.

The multilayer bottle manufactured according to the present invention is:
The transparency is not reduced, the delamination resistance and the impact resistance are excellent, and the ratio of the recycled resin can be increased.
Further, there is no gate portion or gate mark at the bottom, and the vicinity of the center of the bottom is stretched smoothly and uniformly, and no craze occurs.

The virgin resin used in the present invention includes P
A thermoplastic polyester resin such as ET, polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), or a copolymer thereof, or a blend of these resins or other resins is preferably used. Further, various additives such as a colorant, an ultraviolet absorber, a release agent, a lubricant, a nucleating agent, an antioxidant, and an antistatic agent are added to these resins within a range that does not impair the quality of the molded product. You can also.

Among the thermoplastic polyester resins, an ethylene terephthalate thermoplastic polyester such as PET is particularly preferably used. Ethylene terephthalate-based thermoplastic polyesters occupy most of the ester repeating units, generally 70 mol% or more, of ethylene terephthalate units, and have a glass transition point (Tg) of 50 to 90.
C. and those having a melting point (Tm) in the range of 200 to 275C are preferred. PET is particularly excellent in terms of pressure resistance, heat resistance, heat pressure resistance, etc. as an ethylene terephthalate-based thermoplastic polyester, but in addition to ethylene terephthalate units, dibasic acids such as isophthalic acid and naphthalenedicarboxylic acid and diols such as propylene glycol. Copolyesters containing small amounts of the following ester units can also be used.

On the other hand, the recycled resin used in the present invention includes:
A PCR resin obtained by washing, pulverizing, sorting, and regenerating a bottle collected from the market, a scrap (SCR) resin obtained by pulverizing a defective bottle generated in a bottle production plant, and the like can be used. It is preferable to apply the same type of recycled resin as the virgin resin. Also, as recycled resin,
PCR resin or SCR resin can be used alone,
It can also be used as a resin composition in which the same kind of PCR resin or SCR resin is blended with virgin resin. Further, when the intrinsic viscosity (IV) is increased, the same kind of resin having a high IV value may be mixed, and when the resin is colored and used, a colorant may be added to the regenerated resin.

[0026]

EXAMPLES The present invention will be specifically described with reference to the following examples. [Appearance Evaluation Test] Ten multi-layer bottles were extracted and stored at 30 ° C. and 90% RH for 3 weeks, and the center of the bottom of the multi-layer bottle was visually inspected for whitening and craze for occurrence. The number was checked. [Peeling test] The body of the multilayer bottle was 15 mm in width and 50 in length.
mm, and one end of the strip was partially peeled off, and the peel strength was measured with a T-peel strength measuring machine “Tensilon”. [Impact resistance test] A multilayer bottle sealed by adding 500 cc of water was vertically dropped on a concrete floor from a height of 120 cm, and the number of damaged bottles was examined.

(Example 1) PCR having an intrinsic viscosity of 0.72 dl / g obtained by regenerating a PET container recovered from the market
Die temperature 270 ° C, resin pressure 70kgf / c
Conditions melt from an extruder at an extrusion of m ^2, and supplies the PCR resin mass A of 9g into the female mold. Next, a virgin PET resin having an intrinsic viscosity of 0.82 dl / g is melt-extruded from another extruder under the same conditions, and 16 g of the PET resin block B is supplied onto the PCR resin block A in the female mold. The composite resin mass in the female mold is cooperated with the male mold to form a mold clamping pressure of 1
A multilayer compression molding is performed under the condition of 00 kgf / cm ² , and the average thickness of the outer layer in the body is 1.38 mm,
Virgin PET resin having an average body thickness of 1.62 mm in the inner layer of the body, and the weight of the entire preform is 25.
A two-layer preform having a weight of 5.5 g at the mouth and neck including the neck ring was produced. The basis weight of this preform is 25 g, and the proportion of the PCR resin is about 36% by weight.
Met.

Comparative Example 1 PET resin was injected from an injection machine at an injection nozzle temperature of 280 ° C. and a resin pressure of 250 kgf / cm.
Injection molding is performed in a mold under the conditions of ² , to form an intermediate for an inner layer made of virgin PET resin having an average thickness of 1.62 mm in the body. Next, the PCR resin was injection-molded on the outer surface of the intermediate for an inner layer by another injection machine to produce a two-layer preform in which the average thickness of the outer layer in the body was 1.38 mm. The basis weight of this preform was 25 g, and the proportion of the PCR resin was about 36% by weight. still,
The gate was cut within 1 mm.

The two-layer preforms of Example 1 and Comparative Example 1 were heated to an appropriate stretching temperature of 110 ° C., which was equal to or higher than the glass transition point of the PET resin and lower than the melting point.
The mixture was set in a molding die heated to 0 ° C. and subjected to biaxial stretch blow molding to obtain a two-layer bottle having a content of 500 cc.

Table 1 shows the evaluation results of these multilayer preforms and multilayer bottles.

[Table 1]

In the multi-layer bottle manufactured using the multi-layer preform of Example 1, no whitening or craze occurs at the center of the bottom, no delamination between the inner layer and the outer layer occurs, and the gate portion is not formed. Since it did not exist, it had good appearance characteristics. On the other hand, in the multi-layer bottle manufactured using the multi-layer preform of Comparative Example 1, craze occurs at the bottom center part, particularly near the gate part, whitens to milky white, the interlayer strength decreases, and the gate part shifts from the center. Some containers were present.

[0032]

According to the present invention, a predetermined amount of a molten resin mass made of a recycled resin is supplied to the lower part of a female mold, and a predetermined amount of a molten resin mass made of a virgin resin is supplied above the same. By compression molding using a mold and a neck mold, even if the ratio of the recycled resin is large, the transparency is good, there is no whitening of the bottom, there is no gate or gate trace, and the gate cutting process is not performed. A multi-layer preform is unnecessary, the center of the bottom is smooth and uniform, and the neck and neck and the neck ring are made of only virgin resin.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a multilayer preform manufactured according to the present invention.

FIG. 2 is a partial cross-sectional view showing a step of supplying a molten resin mass A of the present invention.

FIG. 3 is a partial cross-sectional view showing a step of supplying a molten resin block B of the present invention.

FIG. 4 is a partial cross-sectional view showing a step before molding in a compression molding step of the present invention.

FIG. 5 is a partial cross-sectional view showing a step after molding in the compression molding step of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Multilayer preform 6 Inner layer 7 Outer layer 11a, 11b Die head 13 Female type 14 Male type 15 Neck type

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) B29L 9:00 B29L 9:00 F term (reference) 4F201 AA24 AA50 AG03 AG07 BA03 BC01 BC02 BC12 BC21 BC25 BM07 BM13 4F208 AA24 AA50 AG03 AG07 LA08 LB01 LG03 LG06 LG13 LG32

Claims (9)

[Claims] 1. A multilayer preform having an outer layer made of a recycled resin and an inner layer made of a virgin resin, wherein the total weight of the multilayer preform is W, the weight of the mouth and neck including the neck ring is X, and the outer layer of the multilayer preform is Where To is the thickness of the inner layer, Ti is the thickness of the inner layer, and Y is the weight ratio of the outer layer, Y = [(W−X) / W] × [To / (To + Ti)] ×
A multilayer preform, wherein a weight ratio (Y) of the outer layer represented by 100 (%) is 25 to 65%. 2. The multilayer preform according to claim 1, wherein the outer layer tip terminates under a neck ring below the mouth and neck. 3. The multilayer preform according to claim 1, wherein the virgin resin is a polyester resin mainly composed of ethylene terephthalate, and the regenerated resin is a post-consumer recycled resin composed of a polyester resin mainly composed of ethylene terephthalate. 4. The method for producing a multilayer preform according to claim 1, wherein no gate portion or gate mark is present at the bottom. 5. A molten resin mass A obtained by melt-extruding a regenerated resin and cutting a predetermined amount is supplied into a female mold, and then a molten resin mass B obtained by melt-extruding a virgin resin and cutting a predetermined amount is formed. After feeding onto the molten resin mass A in the female mold, the male mold is pressed into the female mold and compression molded so that the molten resin mass A forms the outer layer and the molten resin mass B forms the inner layer. A method for producing a multilayer preform, characterized in that: 6. The method for producing a multilayer preform according to claim 5, wherein the virgin resin is a polyester resin mainly composed of ethylene terephthalate, and the regenerated resin is a post-consumer recycled resin composed of a polyester resin mainly composed of ethylene terephthalate. 7. The overall weight of the multilayer preform is W, the weight of the neck and neck including the neck ring is X, the thickness of the outer layer of the multilayer preform is To, the thickness of the inner layer is Ti, and the weight ratio of the outer layer is Ti. When Y is used, the following equation is used: Y = [(W−X) / W] × [To / (To + Ti)] ×
The method for producing a multilayer preform according to claim 5 or 6, wherein the weight ratio (Y) of the outer layer represented by 100 (%) is 25 to 65%. 8. The method for producing a multilayer preform according to claim 5, wherein the outer layer tip ends under a neck ring below the mouth and neck. 9. The method for producing a multilayer preform according to claim 5, wherein a gate portion or a trace of the gate portion does not exist at the bottom.