JPS59115234A - Multilayer vessel - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] - At least a gas permeation-resistant layer such as a saponified vinyl acetate copolymer. It relates to a multilayer container made by hollow-molding a multilayer barison made of two or more layers sandwiched between split-type molds, and more specifically, a multilayer container with excellent peel resistance and excellent gas permeation resistance without humidity dependence. It is related to.

Many of the conventionally used blow-molded containers are made of polyolefin, but due to the characteristics of polyolefin, polyolefin hollow-molded containers have low moisture permeability, low moisture permeability, but high gas permeability, and can be used as containers depending on the application. It did not meet the conditions for sufficient use.

Examples of resins that have properties with fewer such defects, that is, excellent gas permeation resistance, include saponified ethylene-vinyl acetate copolymers (hereinafter referred to as saponified products), polyamides, polyvinyl chloride, polyvinyl alcohol, etc. .

Therefore, for example, if both materials are used to form a multilayer container in which a polyolefin layer and a saponified material layer are laminated, the excellent characteristics of both phases can be utilized to compensate for each other's shortcomings, resulting in a practically useful container. be able to.

However, multilayer containers made by extruding the polyolefin layer and the saponified material layer and integrally molding them in a blow molding die have a problem in that the multilayer parison is sandwiched between the split molds and welded together during blow molding. The wall thickness of the pinch-off portion is thinner, and a saponified layer is exposed to the surface at the end of the pinch-off portion, resulting in poor peel strength.

One of the factors that makes it easy for the layers in instantaneous contact to peel off is that the inner surface of the pinch-off part has a V-shaped cross section, which makes this part thinner.As a means to solve the above problem, It has been known to form a rib /g projecting outward in the pinch-off portion /7 as shown in FIG. 7 to increase the contact area between adjacent layers.

However, by forming ribs as shown in Figure 7,
Although the contact area between adjacent inner layers 79 increases, for example, in the case of a multi-1 m container composed of an inner layer /q made of saponified material and an outer layer 20 made of polyolefin, the inner layer /q is exposed at the tip surface of the rib, and It was difficult to sharpen the ribs because they were relatively thick near the center of the ribs and were not stretched due to blow molding.

The present invention was created in view of the above-mentioned drawbacks, and it is possible to prevent peeling by stretching the saponified layer interposed near the center of the rib without exposing the saponified debris thickly to the tip surface of the IJ rib. The object of the present invention is to provide a multilayer container that is extremely thin so that the influence on strength is virtually negligible, and is also eraseable, and has excellent peel strength and gas permeation resistance.

That is, the multi-layered parison is made of gold by sandwiching and hollow-molding the multilayer J1q barison, which is laminated with at least two layers: a main layer of polyolefin or the like and a gas permeation-resistant surface of saponified material, etc. In a multi-layered container in which ribs are formed on the pinch-off portion formed by being sandwiched between molds, both sides of the ribs are configured to be inclined so as to expand from the base end toward the tip, and the width of the tip is equal to the width of the base end. 77 to 3 times the width, preferably 1.23 to 3 times, and the height of the rib is 0.3 times the width of the proximal end.
~s times, preferably 03 to 3 times,
In addition to increasing the contact area between adjacent layers, just before completely closing the mold, the resin is filled into the rib J recess above the cutout, and the resin near the outer layer that contacts the mold is almost completely inside the rib. In this state, the resin near the inner layer that does not contact the mold is stretched toward the proximal end of the rib, so that the gas permeation resistant layer is not thickly exposed on the tip surface of the rib, and the gas permeation resistant layer is interposed near the center of the rib. It is possible to obtain a multilayer container that has excellent peel strength and gas permeability by making it extremely thin so that its effect on peel resistance is virtually negligible, and even eliminating it. In addition, in the hollow-molded container body, the thickness of the gas permeation resistant layer (where Tb is the thickness of the gas permeation resistant layer,
Ta is the thickness of the main layer, DI is the width of the base end of the rib, and D is the width of the tip of the rib. ° ~ 0 ° Preferably S0 ~. By expanding from the proximal end toward the distal end in the range of 2S0, the resin near the inner layer can be pushed up toward the proximal end of the rib in a desirable state. In addition, in the above formula, X is 03≦X≦0
3, the resin near the inner layer can be pushed up toward the proximal end of the rib in the most desirable state.

In order to push the resin near the inner layer toward the proximal end of the rib as described above, the resin near the blow-molded special outer layer is held in the rib recess located above the mold cutout, and the resin flows from within the rib recess. It is necessary to prevent this from happening. Therefore, it is preferable to form fine irregularities on both inclined surfaces of the rib recess to increase the amount of heat exchange of the resin in contact with the inclined surfaces, so that the resin near the outer layer rapidly cools down. That is, in the rib formed in the pinch-off part, by forming fine irregularities on both sides of the rib, the resin near the blow-molded special layer is held in the rib recess located above the mold cutting part, It can be suppressed from flowing from within the rib recess.

In the present invention, the main layer is a layer made of thermoplastic resin that protects the gas permeation resistant layer and is relatively thick among the container wall layers. Polyolefins with excellent blow moldability such as polyethylene, polypropylene, ethylene-propylene copolymer, polybutene-/, polypentene-/, etc., or modified polyolefins containing polar groups to improve interlayer adhesion, and others. It may be an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid copolymer, an ethylene-meccrylic acid copolymer, or a mixture of these and the above polyolefin.

In the present invention, the gas permeation resistant layer is defined as having an oxygen permeability coefficient of 2.
00cc/1m-m'-,2<7hr(20″C+
6! %, thickness Q, 0.23 mm) or less, and is a layer made of a thermoplastic resin with excellent gas permeability. Examples of the resin include saponified materials, polyamide, polyvinyl chloride, polyvinyl alcohol, and polyacrylonitrile. Or a mixture thereof. The saponified product (saponified ethylene-vinyl acetate copolymer) used in the present invention has an ethylene content of λS ~ 75% and a saponification degree of go%.
As mentioned above, when the ethylene content is lower than 23%, the humidity dependence of gas permeability increases and the processability by extrusion molding decreases, and when the ethylene content exceeds 7%, oxygen scum etc. gas permeability is lost. On the other hand, when the degree of saponification is lower than go%, the permeability to gases such as oxygen gas is lost. In addition, other resins such as polyethylene, polypropylene, ethylene-vinyl acetate copolymers, ethylene-vinyl acetate copolymers, ethylene-acrylic acid copolymers, etc., which have excellent gas permeation resistance, and polar groups can be added to improve interlayer adhesion. It is also possible to use a mixture of modified polyolefins containing modified polyolefins in a range of /IO weight % or less. , bottles, tubes, containers, tank-shaped food containers, industrial chemical containers, and automobile parts such as gasoline tanks.In order to improve the interlayer adhesion between the layers, modified polyolefins containing polar groups and It is also possible to form an adhesive layer made of a mixture of the layer and the resin used for the gas permeation resistant layer.

The specific structure of the notification is as follows: ・・A/B 3 layers・・A/B/A, A/C/B4 layers
・ ・ A/B/A/B,' A/C/B/AS layer・
・A/B/, A/B/A,
It is used in the form of A'/C/B/C/A (where A is the main layer, B is the gas permeation resistant layer, and C is the adhesive layer).

Below, as an example of the present invention, the main layer includes polyolefin,
A multilayer container having a five-layer structure of polyolefin layer/saponified layer/polyolefin layer/saponified layer/polyolefin layer using A7 compound in the gas permeation-resistant layer will be explained based on the drawings.

In FIG. 1, / is a multilayer container showing one embodiment of the present invention, where the inner layer A, the outer layer B, and the middle layer are made of polyolefin; The outer layer S located between and the intermediate a4 is made of saponified material. Further, a rib g is formed on the pinch-off portion 7 of the container to project outward. As shown in FIG. 2, both side surfaces ga and gb of the rib g are formed in an inclined manner so as to widen from the base end 7 toward the distal end 10, and the width Dλ of the distal end 10 is equal to the width D/of the proximal end wa. The height H of the rib g is 03 to 3 times the base end width D/.

If the width D of the tip 10 is lower than 77 times the width of the base end, and if the height H of the rib g is lower than 03 times the width of the base end, the blow molding special mold is completely removed. Immediately before closing, when the excessively filled resin in the rib recess is pushed up in the direction of the proximal end, the layer condition is likely to be disturbed and the peel strength is poor. On the other hand, if the width D2 of the distal end 10 exceeds the width D7 of the proximal end,
In addition, if the height H of the rib g exceeds twice the height, the effect of pushing up the resin in the rib recess toward the proximal end 7 will not work.
The saponified material is thickly exposed at the tip 10, and is also thickly interposed near the center of the rib g in a relatively unstretched state due to blow molding.

In addition, in the hollow-molded container body /a, the wall thickness button, which is the sum of the inner layer 3 made of a saponified material and the outer layer s, is the same as the wall thickness, which is the sum of the inner layer Y, the outer layer B, and the intermediate layer KjJ3 made of polyolefin. Ta to 000~0. Preferably, it is S times. When the wall thickness Tb is lower than 000S times the wall thickness Ta, the wall thickness of the saponified material layer of the entire container becomes extremely thin,
When extruding a multilayer ballisne, there is a risk that pinholes may occur. On the other hand, if the wall thickness Tb exceeds 03 times the wall thickness Ta, there is a drawback that when pushing up the resin filled in the rib recess, the resin will be thick at the center of the rib g even if it is stretched.

Further, it is preferable that the thickness Tb is configured within the following range.

That is, the thickness Tl) of the layer made of saponified material is
If the layer becomes thicker than the thickness Ta of the layer made of insulators, the effect of pushing up the resin filled between the rib recesses must be improved accordingly, and therefore the thickness ratio Tb/Ta
is proportional to the rib width ratio D//Il with a specific coefficient.

In addition, in order to push up the resin after filling the above-mentioned rib recess with the resin, both sides gh and gb of the rib g must be expanded from the proximal end wa toward the distal end 10 in the range of 3° to 1lO0. It is effective to do so.

Further, as shown in FIG. 2, in the rib g formed in the pinch-off portion 7, fine irregularities are formed on both sides ga and gb of the rib g, and the depth of the fine irregularities is 3.
0μ to 7000μ (for example, 30μ for small food bottles)
~Otsu00μ, for large gasoline tanks/100μ~1
00θμ). That is, in order to form fine irregularities on the surface slope of the rib recess and bring the special hollow molded resin into contact with them, and to form fine irregularities that are almost faithful to both sides ga and gb of the rib g to be molded, the depth of the fine irregularities must be adjusted. It is necessary to make the thickness 30μ or more, and if it exceeds 7000μ, the shape of the rib g itself will be damaged and the resin near the inner layer cannot be pushed up well.

Incidentally, the above-mentioned fine irregularities can be any fine irregularities such as a striped pattern, a file pattern, an embossed pattern, etc.

Hereinafter, the process of manufacturing the blood-rich container will be explained based on FIGS. 3 to 6.

// is an extrusion head that extrudes the multilayer parison/ (hereinafter referred to as parison); /, 2 is a split mold; the inner surface of the mold /, 2 is formed with a cavity /3 corresponding to the shape of the container to be molded. On the bottom parting line, a cut-out part /g is formed to sandwich the parison /. /S
is the cutting part/11. Rib recess formed above /
B is an inclined surface formed on both sides of the rib recess/S, and is configured to expand in the direction of the cut-out portion/G, and fine irregularities are formed on the inclined surface/S. In Fig. 3, polyolefin and resin (1 is the extrusion head//
The inner layer 3, the outer layer A and the intermediate JVtll are bonded together in the polyolefin, the inner layer 3 and the outer JITI 5 are extruded as a tidal layer-like parison/made of saponified material,
/ pushed out. By closing the split-type mold /2, the extruded parison / comes into contact with the cutout part /q first, as shown in Fig. 7, and as the opposing cutout part /g approaches, the parison / It was crushed flat,
The surface of the outer layer in contact with the cutout part /l/- and the inclined surface /B rapidly hardens due to heat exchange caused by the contact. In this state, the inner layer B is still kept at a relatively high temperature and the fluidity of the resin is maintained.

As the mold 2 further closes and the cut-out portion 2 approaches, the outer layer 2 is maintained in contact with the entire inclined surface 2, which has fine irregularities, as shown in Figure S. The resin fills the recess/S. Since the unidirectional layer, 2, and intermediate layer have fluidity, as they are knitted, the cut portion/1
1. The inner layer 3 and the outer layer S are separated inwardly and outwardly using the boundary as the boundary, and the inner layer 3 and the outer layer S are joined to each other and constitute an integrated layer within the rib recess/S. As the mold 2 further closes and the recessed part 2 approaches, as shown in FIG.
The resin near the outer layer λ that came in contact with the slope/back is maintained in that state, and the integrated layer made of saponified material located near the center of the rib recess/S is pushed up in the cavity/three directions. Then, it is rapidly stretched and the cutting part/
They are separated using ll as a boundary. Then, the pushed up resin is pushed into the cavity/3 directions and pushed against the fusion surface of the inner layer by being pulled down. When the upper mold 2 is completely closed, the inner JF1.2 comrades at the pinch-off part The two parts are joined together, and the outer parts are joined to a degree that does not affect the strength at least, although this will vary depending on the molding conditions. Further, the inner layer 3° and the outer layer are joined to each other and integrated, and the thickness becomes gradually thinner. The intermediate layer is separated by the integrated layer made of saponified material.

Incidentally, the step of blowing pressure fluid such as compressed air into the parison to expand the parison may be carried out at any time during the process shown in FIGS. 9 to 3.

As described above, the present invention comprises a main layer of polyolefin or the like and a gas permeation-resistant layer of saponified material or the like, and a multilayer parison laminated in two or more layers is sandwiched between split-type molds and hollow-molded. , the multi-layered container is formed by forming ribs on the pinch-off portion formed by sandwiching the multilayer parison between molds, and since the structure of the ribs is a special structure as explained in the example, peel resistance strength is improved. It is possible to provide an excellent multilayer container due to the gas permeation resistant layer that has excellent moisture resistance and no humidity dependence.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway front view of a multilayer container according to the present invention, FIG. 1 is an enlarged sectional view of a pinch-off portion of FIG. 1, and FIGS. FIG. 7 is a schematic diagram of the manufacturing process of such a container, and FIG. 7 is an enlarged sectional view of a pinch-off portion of a conventional container. /Multilayer container Otsu outer layer λ inner layer 7 pinch-off part 3 inner layer
G Ribug middle layer 9 Proximal outer layer 10 Advanced patent applicant Kyoraku Co., Ltd.

Claims (1)

[Scope of Claims] /) At least a main layer such as polyolefin and a gas permeation resistant layer such as saponified ethylene-tl vinyl copolymer,
By sandwiching a multilayer IJ layer stacked to 2 or more layers in a split mold and performing hollow molding, the multilayer parison is sandwiched between the molds and ribs are formed at the pinch-off portion formed. Container G), both sides of the rib are configured in an inclined manner so as to expand from the base end to the tip, the width of the tip is 77 to 8 times the width of the base end, and the height of the rib. A multilayer container characterized in that the width of the proximal end is Q/3- times G. 2) In (1) on the hollow-molded container body, the thickness of the gas permeation-resistant layer is 000S to 03A of the thickness of the main layer,
The patent claim is characterized in that it is configured within the range of the following formula (where Tb is the thickness of the gas permeation resistant surface, Ta is the thickness of the main layer, DI is the width of the base end of the rib, and D2 is the width of the tip of the rib). A multilayer container according to scope 1. 3) In the rib formed at the pinch-off portion, both side surfaces of the rib widen from the proximal end to the distal end within a range of 3° to 0°, respectively. Multilayer container as described. ll) In the rib formed in the pinch-off portion, fine irregularities are formed on both sides of the rib, and the depth of the fine irregularities is set to 30μ to z000μ. Multilayer container.