JP2001323118A - Resin composition having thin-wall part improved in cuttability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding resin composition which can give a molded item having a thin-wall part easily cuttable in unsealing, a sufficient stiffness as a container or lid, and a small molding strain. SOLUTION: This resin composition, improved in cuttability of a thin-wall part, is the raw material for preparing a member having a thin-wall part used in preparing, by injection molding, a pilferproof-type molded item having a structure wherein a container body and lid can not be unsealed unless the thin- wall part is broken. The composition is prepared by compounding 100 pts.wt. polypropylene resin with 10-50 pts.wt. polyethylene produced by the polymerization using a metallocene catalyst. The polypropylene resin is one prepared by block polymerization.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition for injection molding suitable for molding a pill fur proof type container having a thin portion.

[0002]

2. Description of the Related Art A pill fur proof type cap for clarifying the sealing property and unopening property of a package in a molded article is generally used. Among them, a so-called pill fur proof type sealed container (hereinafter, referred to as a container) which is a container manufactured by an injection molding method and which can be opened only by providing a thin portion as a structure of the container and destroying the thin portion. And pill fur proof containers) are widely used. In the case of this type, by clearly recognizing that the thin portion has been opened by breaking the thin portion,
Prank prevention, that is, a pill fur proof package. A pill fur proof package having this type of structure is used in a wide range from a container having a small opening to a container having a large opening.

For example, small-bore containers are widely used, including various bottles and pouches with spouts. FIG. 1 (a) shows a cap C of a spout of a bag-in-box, which is provided with a pill fur proof. This is an example of a type. Grommet G (the spout body) and cap C
Each ratchet mechanism prevents reverse rotation. For opening, the tear-off band 11 connected to the lower part of the cap by the thin part 12 is removed from the knob 15 while the thin part 12 is broken. After that, the cap body is opened by rotating the cap body to the left. By removing the opening band 11, it can be easily recognized that the container has been opened.

In the case of the container shown in FIGS. 2A and 2B, a hinge type lid 30 (lid), which is provided on the rim of the container body 20, is provided.
And an opening band 32 connected via a thin portion 33 to the outer wall portion of the lid having a shape in which the side wall of the opening of the container body 20 is sandwiched between the outer wall 30a and the inner wall 30b of the lid. It is a thing. The opening band is formed by connecting the outer wall portion to the lid main portion 3.
1, the opening band 32, the boundary between the lid main portion 31 and the opening band 32 is a thin portion 33. The projection 21 provided on the outer surface of the container body and the undercut formed by the projection 35 provided on the inner side of the unsealing band are mated to form a sealed container. One side of the opening band 32 is pinched by a finger at a knob 34 at the tip thereof, and the thin portion 33 is broken along the edge of the container body 20. Next, the knob 34 on the opposite side is pinched with a finger, the thin portion 33 is broken along the edge of the container body 20 and the tear-off bands 32 on both sides are removed, and then the knob for lifting the lid is removed. As shown in FIG. 2B, when it is lifted up, it is bent and opened at the hinge portion. Reclosing is possible by clamping the edge of the container body between the inner wall and the outer wall of the lid.

[0005]

In such a lid structure, a thin portion is formed by molding, and the lid cannot be opened unless the thin portion is broken. At the time of opening, the thin portion can be broken only by the force of the fingers, and the type, grade, and the like of the molding resin having good moldability are extremely limited. Further, in the case of a lid having a relatively wide flat top portion 37 as in the example shown in FIG. 2B, distortion in molding tends to appear on the flat portion, and the flat portion is hardened by molding. Later, it may be in a wavy state (curl), and it may be difficult for the user to join with the container body 20 or to perform the re-engagement engagement. In addition, in consideration of environmental issues and the Containers and Packaging Recycling Law, it is required that both the container 20 and the lid 30 be made as thin as possible to reduce the amount of raw materials used.
However, by reducing the wall thickness, the rigidity of the molded product is lost, and the function as a container and the function as a lid are excluded. In addition, the curl phenomenon after the molding tends to occur. SUMMARY OF THE INVENTION An object of the present invention is to provide a technique relating to a molding resin which has a good thinness at the time of opening, has a rigidity as a container or a lid, and has a small molding distortion.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a pill fur proof type molded article having a structure which cannot be opened unless the container body and the lid are destroyed. A resin having improved cuttability of a thin portion, characterized in that a raw material resin for molding a member including 10 to 50 parts by weight of polyethylene polymerized using a metallocene catalyst is used with respect to 100 parts by weight of a polypropylene resin. A composition, wherein the polypropylene resin is a resin obtained by block polymerization.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The resin composition of the present invention will be described in more detail. The thin portion in the present invention particularly means a portion of a preformed container (usually a lid) formed thin so as to be breakable when opening a sealed container, particularly in container packaging. The thin portion includes a portion formed continuously and a portion formed partially. For example,
In the example shown in FIG. 1, the cap body and the ring
Although connected at four thin portions (thin connecting portions), the connecting portions correspond to the thin portions in the present invention. In the example of FIG. 2, the container includes a wide-mouthed container main body 20 and a lid 30 that covers the opening thereof, and the structure of the side wall of the container is, as shown in FIG. The main body 20 includes an inner wall 30b and an outer wall 30a that sandwich a side wall forming an edge of the main body 20, and the outer wall 30a is connected to a lid main portion 31 and an opening band 32 by a thin portion 33. Further, a projection 35 for forming an undercut that fits into a projection provided on the outer wall of the main body container is formed inside the opening band 32. The tip of the opening band 32 is formed to have a thickness that can be cut at hinge portions 36 on the left and right side surfaces of the container. Fig. 2
(C) As shown in the drawing, on the opening start side, the user grips the knob 34 provided on one of the left and right opening bands 32,
While breaking the thin portion, the strip is removed and cut off at the hinge. Next, the tab portion 32 provided on the other opening band 32 is pinched, and the thin portion 33 is broken while the strip portion 32 is removed to remove the lid portion 30.
Can be opened and closed using the hinge portion 36 provided at the base as a bending base point. At the time of reclosing, the lid can be closed by sandwiching the side wall of the container body 20 between the inner wall and the outer wall of the lid.
Note that the thin portion in this example is formed continuously.

[0008] Each of the above-mentioned examples has a structure which cannot be opened unless the preformed thin portion is broken at the first opening of the sealed container. However, since it is broken at the thin portion and is separated from the lid main portion and the opening band, it can be recognized at a glance that the opening has been completed, and the effect of preventing mischief is exhibited.

[0009] The thin portion for opening must be easily broken by the force of a finger applied to a part of the cap or the lid. Furthermore, the molding material resin used in the production of the lid (in some cases, the container body) has stable moldability, and the shape of the molded product is
Even when the top portion has a relatively wide flat portion where molding distortion is likely to occur, it is required that molding distortion is small. The lid (or the container body) is required to have the same rigidity even in a thinner state.

In general, when molded using a resin having rigidity, such as a polypropylene resin, even if the resin is thin, the pill fur proof property of the thin part breaks. ) Became worse and could not be used. Further, for example, when the pill fur proof structure is provided on the periphery of a lid having a wide flat surface as a container lid as shown in FIG. Although low-density polyethylene, or linear low-density polyethylene was used, low-density polyethylene or linear low-density polyethylene, etc., tend to have internal strain in molded products during molding, and therefore, the rigidity in the wide flat portion In addition, the flat portion had to be thick to absorb molding distortion.

The inventors of the present invention have conducted intensive studies on the above-mentioned problems, and as a result of research, have found that a blend obtained by using 10 to 50 parts by weight of polyethylene polymerized using a metallocene catalyst with respect to 100 parts by weight of a polypropylene resin. The present inventors have found that the problem can be solved by using a resin, and have completed the present invention. The present invention includes that the polypropylene resin is a resin obtained by block polymerization. The specific gravity of the metallocene low-density polyethylene is preferably from 0.88 to 0.89. When the ratio of the metallocene resin is less than 10 parts by weight, the thin portion has a poor cutting property and tends to be difficult to open, and the ratio of the metallocene resin is 50%.
Exceeding parts by weight tends to cause molding distortion in molded products,
Rigidity decreases.

In the present invention, the polypropylene resin among the resins to be blended is preferably of a type obtained by block polymerization from the viewpoint of the sharpness of a thin portion. When a homo-type polypropylene was used with respect to the block polymerization type polypropylene, the cutability at the thin portion was insufficient even when molded as a blend resin.

According to the present invention, a molded product having the same rigidity as a molded product of a conventional low-density polyethylene resin or a metallocene-based resin polymerized using a multi-site catalyst and having a reduced thickness at all portions of the molded portion. By doing so, it has become possible to save raw material resin. Further, when the member including the thin portion (usually the lid) has a shape having a wide flat portion, the above-mentioned molding distortion is reduced and the rigidity is improved. Thus, the effect of showing a secure connection in reclosing was confirmed.

As described above, the molding resin in a container having a thin portion for opening is a very limited resin that can be torn off with only the force of fingers. In addition, there is a method of using a screw cap method or a hinge lid method for the reclosing property. In particular, in the case of the hinge lid, the bending resistance of the hinge portion is required. In addition, the pill fur proof property (easy destruction)
Resins used as general lids are low-density polyethylene, linear low-density polyethylene, etc., and these resins have flexibility as physical properties, but due to the problem of moldability, molding distortion is caused by thinning. Practical application has been difficult because it easily occurs. The object of the present invention was able to be solved by using the blend resin of the present invention with a polypropylene and a metallocene resin.

Further, the resin composition of the present invention has good workability in a molding machine, and has no molding distortion and rigidity in a molded shape of a lid (or a container body) obtained by molding. It is.

[0016]

EXAMPLE The cutting performance of the thin portion of the present invention was actually measured.
In order to confirm the effect of the shape, the container and
The lid is molded by the injection molding method, and after filling the contents, the container
The lid is fitted to the main body, and the thin part as the lid is cut,
Other evaluations were made. Hereinafter, common to Examples and Comparative Examples
Mold, mold: rectangular container and top view as shown in FIG.
Lid. Long side 165mm Short side 103mm Depth 83mm at container opening Lid shape: As shown in FIGS. 2 (a) to 2 (e). Thin part 0.2mm Contents: Granular material 1.2kg The physical properties of the resin used are as follows. R0 (block polymerization type polypropylene) MFR: 50 g / 10 min, density: 0.90 g / cm^Three, Tensile yield strength
Sa: 270kg / cm^Two, Bending elasticity: 14.200kg / cm^Two  R1 (block polymerization type polypropylene) MFR: 25 g / 10 min, density: 0.90 g / cm^Three, Tensile yield strength
Sa: 250 kg / cm^Two, Bending elastic modulus: 8.800 kg / cm^Two  R2 (metallocene polyethylene resin) MFR: 2.2 g / 10 min, density: 0.88 g / cm^Three, Tensile yield strength
Height: 33 kg / cm^Two, Flexural modulus: 230 kg / cm^Two  R3 (linear low-density polyethylene) MFR: 31 g / 10 min, density: 0.935 g / cm^Three, Tensile yield strength
Sa: 137kg / cm^Two, Flexural modulus: 2900 kg / cm^Two  [Example 1] Resin used Container body: R0 Lid: A resin obtained by blending R1 and R2 at the following ratio.
did. R1 8 parts by weight R2 2 parts by weight #Blend was performed by a dry blending method. [Comparative Example 1] Resin used: Container body: R0 lid: R1 [Comparative Example 2] Resin used: Container body: R0 lid: R3 <Evaluation of cutability of thin portion>
Attach to the tip and tear the container all around.
Was measured. <Results> (1) The results of the tearability of the thin-walled part are as shown in Table 1.
It is.

[0017]

[Table 1] The cutability of the thin portion was best in Comparative Example 2, and Example 1 was also good. However, Comparative Example 1 was poor in sharpness, and it was difficult for a user who had no force on his / her fingers to open the package at the time of use. (2) Other results were as follows. (Thin-wall moldability) In Example 1, the thin-wall moldability was good. In Comparative Example 2, curl occurred in the lid, and in terms of product quality,
Thin wall molding was not possible. Comparative Example 1 was good in terms of thin-wall moldability. (Curlability) No curl was observed in Example 1 and Comparative Example 1. In Comparative Example 2, when the thickness is reduced,
Curling has occurred. (Bending resistance) In Example 1 and Comparative example 1, the bending resistance was good. Comparative Example 2 is inferior in bending resistance as compared with Example 1 and Comparative Example.

[0018]

According to the present invention, a molded product obtained by injection molding using the resin composition of the present invention having improved thinness of the thin part can break the thin part by a finger.
There is molding stability, and since the obtained molded article has rigidity, it can be made thinner in molding the lid (or the container main body), so that the amount of resin used can be reduced. Therefore, the effect of cost reduction is also shown.
Further, even when the lid has a shape having a relatively wide flat portion, the flat portion does not curl, and there is no trouble that it is difficult to fit the lid.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a container molded using the resin composition of the present invention, (a) a perspective view, (b) a perspective view showing a state in which the opening band is opened and the opening band is separated, and (c). A front view including a partial cross section showing a fitting state of the grommet and the cap, (d) a front view including a partial cross section of the grommet, (e) a cross-sectional view of X ₁ -X ₁ part, and (f) a partial cross section of the cap. Front view including (g)
Y enlarged view, is (h) X ₂ -X ₂ parts cross section.

2A and 2B show another embodiment of a container molded using the resin composition of the present invention. FIG. 2A shows a perspective view, and FIG. 2B shows a state in which an opening band is removed and a lid is raised in an opening direction. Perspective view, (c)
View from G, (d) Opened band removed, (e) X _3-
X ₃ parts is an enlarged cross-sectional view.

[Explanation of symbols]

 B Bag G Grommet C Cap N Inner plug 1 Flange 2 Tube 3 Opening 4 Screw 5 Grommet ratchet 10 Cap body 11 Opening band 12 Thin part 13 Cap ratchet 14 Screw 15 Knob D Contents 20 Container Body 21 Protrusions 30 Lid 30a Outer wall 30a Inner wall 31 Lid main part 32 Opening band 33 Thin part 34 Knob part 35 Projection part 36 Hinge part 37 Top part 38 Undercut part 39 Lifting knob

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3E084 AA05 AA14 AA24 BA01 CA01 CA03 CC04 CC05 CC08 DA01 DA03 DB02 DB09 DB12 DB13 DC04 DC05 DC08 FA09 FB01 FC07 GA04 GA08 GB04 GB08 GB12 GB17 KA13 4J002 BB032 BP021 BP031 GG01

Claims (2)

[Claims] 1. A raw material resin for molding a member including a thin part when a pill fur proof type molded product having a structure that cannot be opened unless the container body and the lid are broken without destroying the thin part. And polypropylene resin
A resin composition having improved cuttability of a thin portion, wherein 10 to 50 parts by weight of polyethylene polymerized using a metallocene catalyst is used with respect to 100 parts by weight. 2. The resin composition according to claim 1, wherein said polypropylene resin is a resin obtained by block polymerization.