JPH0333464Y2 - - Google Patents

Description

[Detailed description of the invention] <Industrial application field> This invention is a coated molded container, more specifically, it has excellent heat insulation properties, cushioning properties, heat resistance, etc., and can maintain a tightly coated state for a long period of time. This invention relates to a coated molded container covered with a foam sheet.

<Conventional technology> In the past, urethane foam or polystyrene foam sheets were cut to an appropriate size and bonded to protect molded containers such as housings for air conditioners in automobiles, air conditioner parts cases, and sinks for stainless steel sinks. In order to protect molded containers that are easily damaged, such as beverage bottles, etc., heat-shrinkable foamed polystyrene sheets can be attached to molded containers with adhesives or foam molded into a predetermined shape that is compatible with the molded containers mentioned above. It is also known that the material is shrunk and covered.

<Problems to be Solved by the Invention> However, since the above-mentioned foam sheets and the like need to be attached or attached with an adhesive, the work of enclosing the molded container is complicated. Further, in the case of the foam sheet, it is necessary to remove the foam sheet etc. from the molded container when the molded container is taken out, and the removal work is complicated. Furthermore, according to the above-mentioned foam sheets and foams, it is difficult to tightly cover the entire molded container by pasting, etc., so the non-stick and attached parts of the molded container are not protected. There is a problem that the effect is not sufficient.

Furthermore, the above-mentioned heat-shrinkable foam sheet does not have sufficient pliability and flexibility, and cannot be tightly packaged along the irregularities, corners, etc. of a molded container. In particular, in the case of products with a high expansion ratio, in order to improve heat insulation and cushioning properties, if the molded container is tightly packed, the heat shrinkage stress of the foamed sheet will be small, so the molded container should be wrapped tightly at the beginning of heat shrinkage. There was a problem that not only was it difficult to package tightly, but also that the foam sheet loosened afterwards, making it impossible to maintain tight contact and sufficient heat insulation and cushioning properties.

This invention was made in view of the above problems, and it is possible to easily and tightly cover even a molded container with a complicated structure, and to maintain a tightly packed state for a long period of time. The purpose of the present invention is to provide a coated molded container that has high heat insulation properties, buffering properties, and heat resistance, and has an excellent protective effect.

<Means for solving the above problems> In order to achieve the above object, the coated molded container of this invention is such that the molded container is covered with a heat-shrinkable coating layer of a heat-shrinkable polyolefin foam sheet having the following performance. It is characterized by the presence of

The foaming ratio is 10 to 80 times, the gel fraction is 20 to 55%, the heat shrinkage rate is 30 to 80%, and the following relational expression [] is satisfied.

3<A/B<50...[] (In the formula, A indicates the maximum shrinkage stress (g/cm ² ) that appears at the beginning of heating when a heat-shrinkable polyolefin foam sheet is heated at 135°C, and B indicates 135 It shows the shrinkage stress (g/cm ² ) 5 minutes after the start of heating when heated at ℃. (The same applies hereinafter.) <Function> This device with the above structure is a heat-shrinkable polyolefin foam sheet. However, since the ratio of the shrinkage stress at the beginning of heat shrinkage to the shrinkage stress after heat shrinkage shows a specific value, when heat-shrinking and tightly covering a molded container, it is possible to quickly and tightly pack the molded container. In addition, the binding force is large, and the heat-shrinkable polyolefin foam sheet will not loosen even after shrink packaging. In addition, since it is made of olefin polymer, it has great flexibility and flexibility, and even molded containers with complex shapes can be packaged tightly following the shape of the molded container. Good followability to containers.
In addition, heat-shrinkable polyolefin foam sheets are
Because it is crosslinked, it has high heat resistance, mechanical strength, etc., and also maintains tensile strength, so the foam sheet covering the molded container will not be deformed even when subjected to external influences such as heat. The molded container can be protected based on the heat insulating properties of the foam sheet.

<Example> This invention will be described in detail below based on the accompanying drawings.

FIG. 1 is a sectional view showing an embodiment of this invention, in which a molded container 1 for accommodating an automobile air conditioner E made of synthetic resin is made of a heat-shrinkable polyolefin foam sheet exhibiting the above-mentioned performance. The foamed sheet 2 is tightly coated by heat shrinking, and the automobile air conditioner E and the molded container 1 are protected by the heat insulating properties, cushioning properties, heat resistance, etc. of the foamed sheet 2.

The olefin polymers constituting the heat-shrinkable polyolefin foam sheet 2 include various polyethylenes such as ultra-low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, and ultra-high molecular weight polyethylene. ;Chlorinated polyethylene;Ethylene-
Propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-α-olefin copolymer, ionomer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-acrylic acid alkyl ester copolymer, ethylene - Copolymers with ethylene monomers such as methacrylic acid alkyl ester copolymers; copolymers of ethylene and crosslinkable vinylsilanes such as trichlorovinylsilane, dichloromethylvinylsilane, dichlorodivinylsilane, γ-methacryloyloxypropyltrimethoxysilane, etc. Ethylene-based polymers such as polymers; examples include polypropylene, chlorinated polypropylene, and polymethylpentene. Among these olefin-based polymers, the above-mentioned polyethylenes with good crosslinking efficiency, particularly low-density polyethylene and copolymers of ethylene and crosslinkable vinyl silane, are preferred. The above copolymer of ethylene and crosslinkable vinylsilane contains 0.01% of crosslinkable vinylsilane.
A copolymer of up to 5% by weight, preferably 0.05 to 1.5% by weight is preferred, and any copolymer such as a random copolymer or a graft copolymer may be used. Moreover, the above-mentioned olefinic polymers may be used alone or in combination of two or more.

Further, the above-mentioned olefin-based polymer can have various molecular weights, but it is preferable to use one having a melt index of 0.05 to 4.0 in order to increase the stress during heat shrinkage and increase the heat shrinkage rate.
If the melt index is less than 0.05, the foaming efficiency during extrusion foaming will decrease, and if it exceeds 4.0, the shrinkage stress during heat shrinkage will be small, which will not only make it impossible to tightly shrink packaging, but also cause problems such as volume thinning. becomes more likely to occur.

Further, the above olefin polymer may be used in combination with other organic polymers. Other organic polymers include acrylic polymers such as polymethyl methacrylate; styrene polymers such as polystyrene, styrene-butadiene copolymer; polyester, epoxy resin, polyurethane, polyamide, polyvinyl acetate; natural rubber, butadiene rubber. , butyl rubber, polyisoprene rubber, and other various rubbers. These organic polymers can be used alone or in a mixture of two or more in a proportion of 50% by weight or less.

The above heat-shrinkable polyolefin foam sheet 2
has a foaming ratio of 10 to 80 times. The foaming ratio is
If it is less than 10 times, the cushioning properties, insulation and heat retention properties, etc. will not be sufficient, and if it exceeds 80 times, creases or wrinkles will remain when shrink packaging, which is not only undesirable in terms of appearance, but also insufficient. However, it is not possible to obtain a product with high mechanical strength. In addition, the foam sheet 2
is obtained by a known method by combining the above olefinic polymer and a blowing agent. As the above-mentioned blowing agent, decomposable blowing agents such as azodicarbonamide can also be used, but volatile blowing agents that have no residue or odor and are not corrosive to metals, such as
Carbon gas, hydrocarbons such as propane, butane, pentane, and hexane, and fluorinated hydrocarbons such as Freon 11 and Freon 12 are preferred. Note that the above foaming agent is used in an appropriate amount, for example, 0.5 to 5% by weight.
Further, the foaming ratio of the foamed sheet 2 can be adjusted by adjusting the extrusion temperature of the olefin polymer, the type and amount of the foaming agent, etc.

Further, the heat-shrinkable polyolefin foam sheet 2 has a crosslinked structure crosslinked by radiation irradiation, etc., and has high mechanical strength, heat resistance, and the like.

The foamed sheet 2 having the crosslinked structure has a gel fraction of 20 to 55%, which indicates the degree of crosslinking. If the gel fraction is less than 20%, the shrinkage stress during heat shrinkage is small, and the heat resistance and mechanical strength are insufficient, resulting in increased volumetric shrinkage during the heat shrinkage process.
This makes it easier for bubbles to burst and for foam sheets to tear. Moreover, if the gel fraction exceeds 55%, only a product with a small heat shrinkage rate can be obtained.

The above-mentioned crosslinked structure may be formed by any crosslinking means, such as chemical crosslinking using peroxides such as benzoyl peroxide, but it is safe, easy to operate, and can efficiently adjust the degree of crosslinking. In addition, it is preferable to use a material crosslinked by electron beam irradiation, which can be mass-produced at low cost. Further, a copolymer of ethylene and a crosslinkable vinylsilane crosslinked by a condensation reaction in the presence of water is also preferable because the crosslinking density can be easily adjusted by adjusting the amount of the crosslinkable vinylsilane used. Products using these crosslinking methods can be easily stretched, have a high heat shrinkage rate and stress, and can also have a high expansion ratio and a large wall thickness. In addition, in order to crosslink the foam sheet by electron beam irradiation, the irradiation dose is preferably 1 to 60 Mrad, particularly 3 to 40 Mrad.

In addition, heat-shrinkable polyolefin foam sheet 2
is formed by being stretched to provide heat shrinkability, and has a heat shrinkage rate of 30 to 80%. More specifically, at 135°C, it is preferably 30 to 80% with respect to the flow direction of the foam sheet, -15 to +15% with respect to the width direction of the foam sheet, and particularly -7 to +7% with respect to the width direction of the foam sheet. If the shrinkage rate in the machine direction is less than 30%, it is difficult to shrink-package the molded container 1, and 80% is the limit at which a heat-shrinkable foam sheet can normally be produced. Furthermore, if the shrinkage rate in the width direction is outside the above range, it is difficult to thermally shrink the material in an attractive manner. The above heat shrinkage rate in the width direction can be obtained without stretching in the width direction, and is within a practically acceptable range for shrink packaging. Further, the heat-shrinkable polyolefin foam sheet 2 may be biaxially stretched, and in this case, for the same reason as the stretching ratio in the width direction, the stretching ratio is 30 to 80% in the machine direction and the width direction. It is sufficient if it has a heat shrinkage rate of 15 to 80%.

Note that the foamed sheet 2 is preferably stretched at a stretching ratio of 1.5 to 5 times so as to exhibit the above heat shrinkage rate. In this stretching, it is preferable that crosslinking is carried out immediately at the same time as the extrusion of the foamed sheet, and then uniaxial stretching is carried out in the flow direction of the foamed sheet.

The heat-shrinkable polyolefin foam sheet 2 may have an appropriate thickness depending on the intended use, but preferably has a thickness of 0.3 to 25 mm, particularly 0.5 to 15 mm. If the thickness is less than 0.3, the cushioning properties, heat insulation, etc. will not be sufficient, and if it exceeds 25 mm, the thermal conductivity will decrease, making it impossible to quickly heat and cool the molded container 1 during stretching or heat shrinking. Problems arise, such as the inability to quickly perform shrink packaging.

When the shrinkage stress of the heat-shrinkable polyolefin foam sheet 2 is measured, the peak value of the shrinkage stress generally appears at the beginning of the measurement, and the shrinkage stress gradually decreases thereafter. The heat-shrinkable polyolefin foam sheet 2 needs to satisfy the following relational expression []: 3<A/B<50...[] Preferably, the range is 3<A/B<30.

When the above A/B is outside the above range, it becomes difficult to perform quick and tight shrink packaging. That is,
Depending on the shape of the molded container 1, it may be difficult to tightly package it, or the foam sheet may become loose.

By using the heat-shrinkable polyolefin foam sheet 2 having large values for both A and B, the molded container 1 can be tightly packaged for a long period of time.

In addition, when the above B value is small, the friction coefficient of the sheet surface increases due to heating during Shrink packaging, and some tackiness develops, so the contact resistance with the molded container 1 and the conveyance roller in the Shrink tunnel increases. This may cause the heat-shrinkable foam sheet to loosen or become partially thin, making it impossible to pack uniformly.
Occasionally, sheets are torn. Moreover, if the heating conditions are excessive, the shape of the bubbles will collapse, the appearance of the package will deteriorate, and the volume will become thinner. On the other hand, if the heating is insufficient, shrinkage will not be sufficient, and therefore it will not be possible to obtain a molded container 1 that is in close contact with the molded container 1, making it difficult to adjust the heating conditions.

In order to satisfy the above conditions and maintain the tightly packed state of the molded container 1 for a long period of time, it is preferable that the heat-shrinkable polyolefin foam sheet 2 satisfies the following relational expression [].

A x foaming ratio > 4000 B x foaming ratio > 400 ... [] In the above formula [], the value of A x foaming ratio is
If it is less than 4,000, the tightening force at the beginning of heat shrinkage is small and rapid shrinkage is not performed, making it difficult to shrink-pack the molded container 1. Moreover, if the value of B×expansion ratio is less than 400, various troubles may occur in the shrink tunnel, or it may be difficult to maintain the molded article 1 in a tightly packed state after shrink packaging.

In addition, the heat-shrinkable polyolefin foam sheet 2 having the above-mentioned performance is obtained by following the foaming and crosslinking steps:
It can be produced by stretching using the roll stretching method described below. That is, the stretching is
As shown in FIG. 2, the first roll 11 has a different rotational speed and surface temperature, is spaced apart from each other by a predetermined distance D, has a radius r ₁ , and heats the foam sheet 13; r ₂ and a second roll 12 that stretches and cools the foamed sheet 13 that has passed through the first roll 11;
The rotational speed of the roll 12 of the first roll 11 is
By making the first roll 11 larger than
A foam sheet 13 having a thickness t is sent to
is stretched in the machine direction into a foamed sheet 13 having a thickness t ₀ . Then, the foamed sheet 13 is stretched so as to satisfy the following relational expression.

0≦L<30t ₀ (In the formula, L is the difference between the surface of the first roll 11 and the surface of an imaginary cylinder that is the sum of the radius r ₂ of the second roll 12 and the thickness t ₀ of the foam sheet after stretching. (indicates the distance between tangents) In the above relational expression, if L is outside the above range,
Not only is rapid stretching not carried out within a short period of time, but
It cannot be moved to the cooling zone within a short time, and stretching due to shear deviation between the front and back surfaces of the foam sheet is unlikely to occur. Therefore, it becomes difficult to obtain a heat-shrinkable polyolefin foam sheet 2 with large heat-shrinkage stress. Furthermore, for the same reason as above,
In the stretching process, the distance D between the rolls 11 and 12 is
is preferably carried out under conditions that satisfy the following relational expression.

0.5mm<D<70mm According to the roll stretching method described above, the foamed sheet 13 having heat insulation and heat retention properties can be quickly heated and cooled, and shearing force is also applied between the front and back sides of the foamed sheet 13 to stretch the foamed sheet 13. In the foamed sheet 13, not only the molecular orientation but also the shape of the cells and the arrangement of the cells are oriented, so that a heat-shrinkable polyolefin foamed sheet 2 having a large heat-shrinkage stress can be obtained.

In the roll stretching method, the temperature of the first roll 11 is higher than the melting point of the olefin polymer constituting the foamed sheet 13, preferably within a temperature range not exceeding 50°C above the melting point of the olefin polymer. and the second roll 12
The temperature is set below the melting point of the olefinic polymer constituting the foamed sheet 13, particularly below 100°C.

Note that the heat-shrinkable polyolefin foam sheet 2 described above may be laminated with other films or sheets. The materials for the films and sheets mentioned above include various synthetic resins such as olefin polymers such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate, styrene polymers such as polystyrene and styrene-butadiene, nylon, polyvinyl chloride, and polyvinylidene chloride. Examples include films and sheets. Further, the above-mentioned film or sheet may be non-foamed or foamed, and it is preferable that the film or sheet has heat-shrinkability after being stretched. It may also be one that has been given contractility. These films and sheets may be laminated by co-extrusion with the resin material of the film or sheet and heat fusion, or by lamination using an appropriate adhesive such as ethylene-vinyl acetate copolymer or polyurethane. good. Also, as an adhesive,
In addition to the above-mentioned ethylene-based polymers that are crosslinked by radiation irradiation, resins having unsaturated double bonds such as polybutadiene, epoxy acrylates, urethane acrylates, polyester acrylates, or their methacrylates can be used to Since these adhesives can also be crosslinked along with crosslinking, the integrity of the laminated sheet is increased.

The coated molded container of this invention can be obtained by surrounding the molded container 1 with the above-mentioned heat-shrinkable polyolefin foam sheet 2 by heat sealing or the like, and heat-shrinking it at a temperature of about 100 to 250°C. In addition, the heat-shrinkable polyolefin foam sheet 2
Not only in sheet form, but also in molded containers 1 due to heat shrinkage.
Preferably, the material is previously formed into a cylindrical or bag shape so that it can be easily tightly packaged. Further, in order to perform the shrink packaging operation smoothly, an appropriate number of air vent holes, cuts, etc. may be formed in the heat-shrinkable polyolefin foam sheet 2.

The molded container 1 constituting the above-mentioned coated molded container includes a bottomed container formed by a molding method such as extrusion blow molding, injection molding, or thermoforming using a sheet;
Various molded containers are used, such as a closed cavity container whose inside is sealed, a window-opening cavity container partially having a window or a hole, and a hollow container made by combining a plurality of divided molded products. In addition, when closely covering the above-mentioned window-opening hollow body container such as a car air conditioner case, a portion corresponding to the above-mentioned window portion etc. may be cut out.

In addition, by covering with the heat-shrinkable polyolefin foam sheet 2, molded containers made of materials with insufficient heat resistance such as polyethylene and polypropylene, synthetic resins such as various engineering plastics, metals, etc. Molded containers having complex shapes such as uneven parts can be effectively protected. More specifically, the heat-shrinkable polyolefin foam sheet 2 has high heat-insulating and heat-retaining properties, cushioning properties, heat resistance, mechanical strength, etc., as well as high heat-shrinkage stress and flexibility as described above. This prevents condensation on air conditioner housings, air conditioner parts cases, beverage bottles, ceramics, porcelain, thermal bottles, thermal boxes, sinks such as stainless steel sinks, molded containers such as tray water tanks, etc. can be reliably protected.

<Effects of the invention> As described above, according to this invention, a heat-shrinkable polyolefin foam sheet is used in which the ratio of the shrinkage stress at the beginning of heat shrinkage to the shrinkage stress after heat shrinkage has a specific value. Even if the molded container has a complicated shape, it can be quickly and strongly heat-shrinked without causing trouble during shrink packaging, resulting in excellent adhesion between the coating layer and the molded container. In particular, even as a heat-shrinkable polyolefin foam sheet with a high expansion ratio, the molded container can be tightly shrink-wrapped immediately after heat shrinkage, and even after shrink-wrapping, the tightly packed state can be maintained without any loosening. Ru. Also,
The material of the foam sheet is an olefin-based polymer that is flexible and pliable, so unlike rigid polystyrene-based foam sheets, it can easily conform to molded containers with complex structures during heat shrinkage. It is easy to coat molded containers tightly and is easy to use. Therefore, not only can molded containers be tightly coated easily and reliably without using adhesives, but also molded containers having various shapes can be easily and economically applied. Furthermore, since the molded container is covered with the foamed sheet that is cross-linked and has high heat resistance, mechanical strength, heat insulation and heat retention, etc., the foamed sheet not only does not deform, but also ensures that the molded container remains stable for a long time. This invention has the unique practical effect of being protected for a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of this invention, and FIG. 2 is a schematic view showing the stretching process of a heat-shrinkable polyolefin foam sheet. 1... Molded container, 2... Heat-shrinkable polyolefin foam sheet.

Claims (1)

[Claims for Utility Model Registration] 1. A covered molded container, characterized in that the molded container is covered with a heat-shrinkable coating layer of a heat-shrinkable polyolefin foam sheet having the following properties. Foaming ratio 10 to 80 times, gel fraction 20 to 55%, heat shrinkage rate 30 to 80%, and the following relational expression []
something that satisfies 3<A/B<50...[] (In the formula, A indicates the maximum shrinkage stress (g/cm ² ) that appears at the beginning of heating when a heat-shrinkable polyolefin foam sheet is heated at 135°C, and B indicates 135 ℃
² ) The above utility model, in which the heat-shrinkable polyolefin foam sheet satisfies the following relational expression [ ]: A coated molded container according to claim 1. A x Expansion ratio > 4000 B x Expansion ratio > 400 ... [] 3. The covered molded container according to claim 1 of the above utility model registration claim, wherein the heat-shrinkable polyolefin foam sheet is made of an ethylene polymer. 4. The coated molded container according to claim 1, wherein the heat-shrinkable polyolefin foam sheet is crosslinked by electron beam irradiation. 5. The covered molded container according to claim 1, wherein the heat-shrinkable polyolefin foam sheet is obtained by crosslinking a copolymer of ethylene and crosslinkable vinylsilane in the presence of moisture. . 6. The covered molded container according to claim 1, wherein the heat-shrinkable polyolefin foam sheet is formed into a cylindrical or bag shape. 7. The coated molded container according to claim 1, wherein the molded container is a synthetic resin molded container.