JPS60157825A - Hinged blow formed item - Google Patents

Abstract

PURPOSE:To obtain a hinged blow formed item excellent in hinge characteristics and surface characteristics by a method wherein a hinge section obtained by compressing and thinning resin compound composed of polypropylene and specified polyethylene is incorporated with a hollow body. CONSTITUTION:Polypropylene and polyethylene of linear molecular structure having densities 0.91-0.93g/cm<3>, melting points 115-130 deg.C, preferably, 119- 127 deg.C, thermal conductivities 6X10<-4>-9X10<-4>cal/sec.cm<2>. deg.C.cm are mixed to obtain resin compound. A hinge 3 obtained by compressing and thinning said compound is incorporated with a hollow main body to obtain a hinged blow formed item.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a hinge blow-molded product made of a resin composition of a mixture of polypropylene and polyethylene, which is used as a case, housing member, etc., and more specifically relates to hinge characteristics. and hinges with surface properties (related to blow-molded products).

[Prior art]

Conventionally, a blow molded product (hereinafter referred to as a hinged blow molded product) constructed by integrally connecting hinges having a thickness of 1ii S>1 is disclosed in Japanese Patent Publication No. 18748/1983.

In the above-mentioned conventional examples, molded articles made of polyethylene are used for applications requiring impact resistance, and molded articles made of polypropylene are used for applications requiring heat resistance.

Compared to hinged blow-molded products made of polypropylene, hinge-1 blow-molded products made of polyethylene have problems such as inferior hinge properties, especially in repeated bending resistance, and the parison comes into contact with the cavity surface of the mold during blow-molding. When molding a hollow body, cooling and solidification proceed before the surface of the parison is completely molded along the minute irregularities such as a grain pattern formed on the cavity surface, so the reproducibility of the surface characteristics, especially the surface appearance, is affected. There is a problem that is worse than that. This problem,
A blow-molded product with a hinge made of polypropylene will solve this problem to some extent, but on the other hand, the bending points of the hinge will be concentrated on the right edge of the hinge, which is biased to one side in the width direction, resulting in poor hinge properties, especially planar flexibility. For example, if the hollow body is a case consisting of a body and a lid, the trajectory drawn when opening and closing the lid may deviate from the designed trajectory, and when the body and lid are closed, there is a risk that the mating surfaces may become misaligned. Ta. Also,
Due to the high fluidity of polypropylene when melted, a drawdown phenomenon was observed when extruding the parison, resulting in poor blow moldability and the risk of uneven thickness of the hollow body.

Among the above problems, as a means to prevent drawdown development, low density polyethylene has been added to polypropylene.
．． It is shown in JP-A-53-79939 that blow moldability is improved with a resin composition mixed with 1 to 20% by weight. That is, the reason why the drawdown phenomenon can be prevented in the above-mentioned publication is that by mixing low-density polyethylene with excellent blow moldability, the drawdown phenomenon is eliminated to a certain extent compared to polypropylene alone. However, as described in the above-mentioned publication, when the content of low density polyethylene exceeds 20%, the compatibility rapidly decreases, resulting in disadvantages such as a decrease in blow moldability and a decrease in the surface appearance of the molded product. Furthermore, when obtaining a hinged blow-molded product as in the present invention using the above resin composition, the hinge properties such as repeated bending resistance and the surface properties such as surface appearance reproducibility are not improved, and the hinge properties and surface properties are not improved. A hinged blow-molded product that has excellent properties on both sides has been desired.

[Purpose of the invention]

The present invention was conceived in view of the above, and provides a hinged blow-molded product for use as cases, housing members, etc., which has excellent hinge properties such as repeated bending resistance, and excellent surface properties such as surface appearance reproducibility. This is what we provide.

[Structure of the invention]

The present invention is composed of a resin composition that is a mixture of polypropylene and polyethylene, and the polyethylene has a density of 0.91 to
It consists of a linear molecular structure with a melting point of 0.93 g/Cm3 and a melting point of 115° C. or higher, and is characterized in that it is composed of a hinge portion made of the above-mentioned desk fat composition and whose thickness has been reduced by compression, and which is integrally connected to a hollow main body. This invention relates to a hinged blow molded product.

That is, the resin composition used in the present invention is composed of polypropylene and a multi-branched molecule having a long chain branch with a melting point of 110 to 113° C. Compared to a mixture with polyethylene, which has a structure, it has excellent compatibility, and even if 20% by weight or more of polyethylene is mixed with polypropylene, the compatibility will not drop sharply.

In addition, the compressed thin-walled hinge with molecular orientation in the bending direction has excellent hinge properties such as repeated bending resistance and planar bending properties, and also provides a hinged blow-molded product with excellent surface properties such as surface appearance reproducibility. be able to.

[Summary of the invention]

The hinged blow molded product according to the present invention can be applied to cases, housing members, trays, containers, bottles, tanks, other automobile parts, light electrical parts, construction parts, and the like.

FIGS. 1 to 3 show an example thereof. FIG. 1 shows a cover member as an example of a hinged blow-molded product, and the cover member 1 of a hollow double-walled container and the bracket 2 for mounting to the container (not shown) are compressed thin and bent. They are integrally connected at a hinge part 3 whose molecules are oriented in the direction.During blow molding, the surface of the cover member 1 is coated with 0.01 A grain pattern with a depth of ~0.4 mm is formed, and the hinge part 3 is formed by compressing parisons overlapped during blow molding with a mold to a depth of 0.2~9 mm.
．． It is formed to a thickness of 8 mm, preferably 0.4 to 0.6 mm. FIG. 2 shows a case in which a hollow double-walled main body 1a and a lid 2a are integrally connected at a hinge part 3a, and the lid 2a and a case locking latch 4 are connected to a hinge part 3b.
They are connected together. FIG. 3 shows a tank, and connects the hollow tank body 1b and the handle 2b to a hinge part 3C.
They are connected together.

The hinge (=1 blow molded product) as shown above is made by melting a resin composition that is a mixture of polypropylene and polyethylene having a linear molecular structure with a density of 0.91 to 0.93 g/cm'' and a melting point of 115°C or higher. extruded as parison,
It is then obtained by blow molding.

In the present invention, polypropylene refers to a polymer of propylene alone, a random copolymer of propylene and 30 mol% or less of other monomers, such as ethylene, vinyl ester, etc., or a black copolymer. It consists mainly of a linear molecular structure with short chain branches. In addition, in the present invention, the melting point is 165 to 180°C, the density is 0.88 to 0.92
g/cm3, thermal conductivity 3Xl (1-'~6X10-'c
al/5ec-c102・℃・(', m polypropylene is applied.

The polyethylene used in the present invention is a German polymer of ethylene produced by a low-pressure method, or a polymer containing ethylene and 30 mol% or less of other fil, such as propylene, butene, acrylic acid, vinyl acetate, etc. It is a random copolymer or block copolymer with mainly short chain branches and a flocculent molecular structure with a relatively narrow molecular weight distribution. Further, in the present invention, the melting point is 115 to 130°C, preferably 119 to 127°C, and the density is 0.91 to 0.93°C.
g/cm3, thermal conductivity 6XlO-'~9XlO
-'cal/sec-cm"・℃・CIl+ polyethylene is applied. Even if the above-mentioned polyethylene is mixed with polypropylene, the tensile strength and surface texture of the polypropylene itself will be extremely reduced. In addition, the hinge has excellent deformation resistance, and the hinge does not stretch excessively due to tensile stress during use.In addition, the polyethylene used in the present invention has a tensile strength at break (AS7F
M-D-638) is 220 kg/cm2 or more, preferably 240 kg/cm2 or more.

That is, the polyethylene used in the present invention has a density of 0.94 g/cm" produced by the conventional low pressure method.
The above-mentioned high-density polyethylene and low-density polyethylene produced by a high-pressure method and having a melting point of less than 115° C. and a density of 0.94 g/Cm or less mainly consisting of a multi-branched molecular structure having long chain branches are excluded.

The resin composition of the present invention, which is a mixture of polypropylene and polyethylene, may contain additives such as colorants, lubricants, stabilizers, antioxidants, and antistatic agents to the extent that the hinge properties and surface appearance properties are not impaired. May be mixed. Also,
The polypropylene and polyethylene used in the present invention have excellent compatibility, and even if polyethylene is mixed with 20% by weight or more, the compatibility will not decrease sharply, and the % by weight, preferably 10
~80% by weight of polyethylene can be mixed.

Furthermore, the polyethylene used in the present invention is conventional low-density polyethylene, that is, produced by a high-pressure method, and has a density force of 0.94.
It has a higher melting point than polyethylene with a g/cm3 or less, and therefore approaches the melting point of polypropylene,
Additionally, the tensile strength is improved and the surface hardness is high. On the other hand, conventional high-density polyethylene, i.e., produced by a low-pressure method, has a density of 0.
It has a lower thermal conductivity than polyethylene with -94 g/co- or more.

The hinged blow-molded product according to the present invention has excellent hinge properties such as repeated bending resistance, planar flexibility, and hinge strength, and excellent surface properties such as surface appearance reproducibility and surface hardness. The hinged blow molded product according to the present invention has excellent surface appearance reproducibility, and can faithfully reproduce minute irregularities such as grain patterns, embossed patterns, and fine engravings on the surface of the hollow body, for example. However, this is an example of excellent surface appearance reproducibility, and the hinged blow-molded product according to the present invention can also be applied to applications where a smooth surface is formed without grains or the like.

(Left below) [Examples and Comparative Examples] A resin composition obtained by mixing the resins shown in Table 1 at the mixing ratio shown in Table 2 was used, and Screej1. -Diameter 90mm
(L/D=18) extruder, wall thickness 3mm, outer diameter 2
Extrude a parisson of 00 mm to a depth of 9.0 mm on the cavity surface.
The parison was closed using a split mold with a grain pattern of 2 mm minute unevenness, and the blowing pressure was 5 kg/c.
By blow molding with m2 and removing excess material, a container consisting of a cover member (hollow body) 1 and a mounting bracket 2 connected together with a hinge 3 as shown in FIG. A lid (blow molded product with hinges) was obtained. The cover part kA'l of this molded product is 400mm long and 28mm wide.
9 m sn, overall thickness 23 mm, average wall thickness 2.2 mm
, Bracket 2 is 280mm long, 2Qmm wide, overall
V width 3 st+ m, hinge 3 is length 280mm, width 4
m■■+, average wall thickness Q, 5rnrn, and the weight of the molded product was about 520g.

Table 2 shows the hinge characteristics and surface appearance characteristics of each Example and each Comparative Example obtained by the above method.

Table 1 - Surface of resin used, melting point ("C") and density (g/cm") are ΔS1"M
-11-1505, thermal conductivity (10-'c a l /
sec'cm" - "c・cm is ASTM-(, -17
Based on 7 test methods.

Table 2 - Characteristic measurement results Characteristics A to D of each Example and each Comparative Example shown in Table 2 were measured according to the following measuring method.

Characteristic A (Planar bendability of hinge) The bending point of the hinge is determined when the hollow body is fixed, the bracket is gripped, the bracket is rotated 180° to the hollow body side, the hinge is bent, and the action of restoring the hinge is repeated five times. Observe. O in the table
indicates that the hinge was curved and bent almost uniformly in the width direction, △ indicates that the bending point occurred at the central part of the hinge in the width direction, and × indicates that the hinge was bent at one end in the width direction. Indicates that an inflection point has occurred.

Characteristic B (repetitive bending resistance of hinge) Using each molded product after measuring characteristic A, fix the hollow body and hold the bracket in a jig that can rotate 180 degrees, and rotate the bracket 180 degrees with the hinge as the rotation axis. The hinge is bent by repeatedly rotating it within a range of 100° to 100°, and the number of times the hinge is bent until it breaks to a length of 10% of the hinge length in the longitudinal direction of the hinge is measured. ○ in table
indicates bending times of 30,000 times or more, △ indicates bending times of 10,000 times or more, and × indicates bending times of less than 10,000 times.

Characteristic C (Hinge Strength) The tensile strength at break per 1 cm of hinge length of each molded product is measured.

In the table, ○ means 13.5 kg or more, △ means 12 kg or more13.5
kg, × indicates a tensile strength of less than 12 kg.

Characteristic D (Surface reproducibility of hollow body) Observe the surface appearance of each molded product. In the table, ○ indicates that the grain of the mold is well reproduced, Δ indicates that the grain of the mold is almost well reproduced, and × indicates that the grain is hardly reproduced and is in a poor state.

〔Effect of the invention〕

As mentioned above, the lunch blow-molded product of the present invention has excellent hinge properties such as repeated bending resistance, planar bendability, tensile strength, and deformation resistance, and the hollow body has excellent surface appearance reproducibility, surface hardness, and texture. It has excellent surface properties such as, and can be used in a wide range of fields such as cases and housing members.

[Brief explanation of the drawing]

Figures 1 to 3 show an example of a hinged blow-molded product according to the present invention, in which Figure 1 is a perspective view of a cover member, Figure 2 is a perspective view of a case, and Figure 3 is a tank. FIG. 1 Two cover parts 2 Ni bracket 3: Hinge part Patent applicant Kyoraku Co., Ltd.

Claims (1)

[Claims] It is composed of a resin composition that is a mixture of polypropylene and polyethylene, and the polyethylene has a density of 0.91 to 0.93.
g/crrt 3, a hinge consisting of a linear molecular structure with a melting point of 115° C. or higher, and comprising a compressed thin hinge portion made of the above resin composition and integrally connected to a hollow main body. Blow molded product.