JP2001164019A - Foamed sheet and container by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet excellent in impact resistance, heat resistance, heat insulation and oil resistance, and a container formed from the sheet. SOLUTION: This sheet is produced by forming a foamed sheet containing a homo or copolymer of a cyclic olefin and having 1.1-10 fold blowing magnification, and the container is produced by using the same sheet. The above foamed sheet is allowed to contain an olefin polymer (especially a polyethylene having >=0.5 g/10 min melt flow rate) in a ratio of (the cyclic olefin polymer)/(the olefin polymer)=((99.9/0.1)-(50/50) (in weight ratio).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet excellent in impact resistance, heat resistance, heat retention and oil resistance and a container formed from the sheet.

[0002]

2. Description of the Related Art In recent years, it has been well known that a foamed sheet is formed from a polyolefin resin such as polyethylene or polypropylene, which is lightweight and has heat resistance, oil resistance and heat insulation properties as a container in the food field.

For example, a foamed sheet composed of crystalline polypropylene, a polyolefin having a specific melting point and an inorganic filler (Japanese Patent Publication No. 2-36141), and a foamed sheet composed of polypropylene, polystyrene, an inorganic filler and a styrene-based elastomer (ex. Japanese Unexamined Patent Publication No. Hei 11-80402), a foamed sheet comprising an ethylene-propylene block copolymer and a styrene-based elastomer (Japanese Patent Laid-Open No.
No. 107317) is known. However, these foamed sheets are liable to cause a molding trouble due to a drawdown phenomenon due to heating at the time of molding the container. Further, in the case of deep drawing, it is difficult to make the thickness of the corner portion of the container uniform, and the thickness of the container tends to be uneven.

In order to improve these drawbacks, a method of incorporating a radical generator into a polyolefin and irradiating it with ionizing radiation (JP-A-6-32929 and JP-A-5-339411) has been proposed. Foam sheet made of polypropylene (Japanese Patent Application Laid-Open No. 8-259721)
Etc. have been proposed. However, the formability of these sheets is not sufficient. In addition, rigidity, impact resistance and molecular weight are reduced by re-extrusion of the recycled product.

Also, a foam of a cyclic olefin resin composition comprising a specific modified ethylene-α-olefin copolymer, a specific cyclic olefin random copolymer, and a specific ethylene-α-olefin copolymer (particularly, Kaihei 6-172
572) is known to be excellent in thermoformability, heat resistance and the like. However, this foam cannot simultaneously satisfy physical properties such as heat resistance and heat retention and mechanical properties.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a plastic sheet excellent in both heat resistance and impact resistance, and a container using the same.

Another object of the present invention is to provide a plastic sheet excellent in heat resistance and heat retention and a container using the same.

It is still another object of the present invention to provide a plastic sheet having excellent heat resistance and oil resistance and a container using the same.

Another object of the present invention is to provide a plastic sheet having excellent heat resistance and moldability and a container using the same.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, a foamed sheet containing a homo- or copolymer having a cyclic olefin in the main chain has been found to have heat resistance and impact resistance. The inventors have found that both properties are excellent, and have completed the present invention.

That is, the foamed sheet of the present invention is a foamed sheet containing a homo- or copolymer having a cyclic olefin in the main chain. The cyclic olefin polymer is represented by the following formula (1)
It may be at least one selected from the polymers represented by (7). The foamed sheet further contains an olefin polymer (especially polyethylene having a melt flow rate of 0.5 g / 10 min or more) in a ratio of cyclic olefin polymer / olefin polymer = 99.9 / 0.1 to 50/50 ( Weight ratio). The foamed sheet has a sheet expansion ratio of about 1.1 to 10 times, and a number of cell membranes per unit thickness in a direction orthogonal to the sheet extrusion direction is about 1 to 50 / mm, The dimensional change rate (Mh) in the sheet flow direction after heat treatment at 130 ° C. for 30 seconds and the dimensional change rate (Th) in the direction orthogonal to the sheet flow direction are each about ± 10% or less. The thickness is about 0.1 to 3 mm. The foamed sheet may be formed by laminating at least two sheets of the same or different materials.

[0012]

Embedded image

(Wherein R ^{1 to} R ⁵ are the same or different,
X represents a hydrogen atom, a halogen atom, an alkyl group, an acyl group such as an acetyl group, an ester group or an alkoxyl group;
Represents an integer of 0 or more, and Y represents a natural number. In particular, R ³ is a hydrogen atom or a methyl group.) The present invention also includes a container formed of the foam sheet.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The foamed sheet of the present invention is a foamed sheet containing a homo- or copolymer of cyclic olefin,
It may further contain an olefin polymer.

[Cyclic olefin polymer] The cyclic olefin polymer has a cyclic olefin unit in the main chain. Examples of the cyclic olefin include cycloalkylene, cycloalkenylene, cycloalkynylene, polycyclic olefin, and the like.

Examples of the cycloalkylene include C _3-10 cycloalkylene such as cyclopropylene, cyclobutylene, cyclopentene, cyclohexene and cyclooctene, and derivatives thereof.

The cycloalkenylene includes, for example, C, such as cyclopropenylene, cyclobutenylene, cyclopentenylene, cyclohexenylene and cyclooctenylene.
Examples thereof include _3-10 cycloalkenylene and derivatives thereof.

Examples of the cycloalkynylene include, for example, cyclopropynylene, cyclobutynylene, cyclopentynylene, cyclohexynylene, cyclooctynylene and the like.
Examples thereof include _3-10 cycloalkynylene and derivatives thereof.

Examples of the polycyclic olefin include norbornene, ethylidene norbornene, dicyclopentadiene, dicycloheptadiene, tetracyclododecene,
Hexacycloheptadecene or derivatives thereof and the like.

These cyclic olefins can be used alone or in combination of two or more.

The cyclic olefin polymer may be a homopolymer of the above-mentioned cyclic olefin or a copolymer of a cyclic olefin and a monomer copolymerizable therewith.

Examples of the copolymerizable monomer include an olefin monomer and a vinyl monomer.

Examples of the olefinic monomer include ethylene, propylene, allene, 1-butene, butadiene, 1-pentene, 1-hexene, 1-heptene,
Examples include linear C _2-10 olefins such as octene, and branched C _3-6 olefins such as isobutene and isoprene. Of these, linear C _2-6 olefins are preferred.

Examples of the vinyl monomer include vinyl esters, vinyl ethers, halogen-containing vinyl monomers, (meth) acrylic acid monomers and the like.

As vinyl esters, vinyl acetate,
Examples include vinyl alcohol and vinyl acetal.
Examples of vinyl ethers include C _1-3 alkyl vinyl ethers such as methyl vinyl ether and ethyl vinyl ether. Examples of the halogen-containing vinyl monomer include vinyl chloride and vinylidene chloride. Examples of the (meth) acrylic acid-based monomer include (meth) acrylic acid, (meth) acrylic acid esters (such as alkyl (meth) acrylates such as ethyl (meth) acrylate), and (meth) acrylonitrile. .

These copolymerizable monomers can be used alone or in combination of two or more.

The ratio (molar ratio) of the cyclic olefin to the copolymerizable monomer is as follows: cyclic olefin / copolymerizable monomer = 100/0 to 10/90, preferably 90/10
It is about 50/50.

The homo- or copolymer of the cyclic olefin is at least one selected from the polymers represented by the above formulas (1) to (7), and is a polymer having low crystallinity or non-crystallinity. preferable.

The number average molecular weight of the cyclic olefin polymer is
100 to 10,000,000, preferably 1,000
It can be selected from a range of about 1,000,000.

[Olefin polymer] Examples of the olefin polymer include ethylene, propylene, allene, 1-
Butene, butadiene, 1-pentene, 1-hexene, 1
Α-linear C _2-10 olefins such as heptene and 1-octene, and branched C _3-6 olefins such as isobutene, 4-methyl-1-butene, 3-methyl-1-pentene and isoprene; A homopolymer or a copolymer, a copolymer of an olefin and a copolymerizable monomer, and the like are included.

Among these olefin polymers, ethylene polymers containing ethylene units as a main component (for example, 75 to 100% by weight) (for example, low-density polyethylene, linear low-density polyethylene, medium-density polyethylene,
Polyethylene such as high-density polyethylene, ethylene-propylene copolymer, ethylene-propylene-butene-1 copolymer, ethylene-vinyl acetate copolymer, ethylene-butene-1 copolymer, ethylene- (4-methylpentene-
1) a copolymer, an ethylene- (meth) acrylate copolymer or an ionomer thereof, an ethylene- (meth) acrylate copolymer such as an ethylene-ethyl acrylate copolymer, etc.), and a propylene unit as a main component ( For example, 75-
(For example, polypropylene such as atactic polypropylene, propylene-ethylene copolymer, propylene-butene-1 copolymer, propylene- (meth) acrylic acid copolymer or its ionomer). , Maleic anhydride polypropylene, etc.), and particularly, a melt flow rate of 0.5 g / 10
More than one minute of polyethylene is preferred.

These olefin polymers can be used alone or in combination of two or more.

The number average molecular weight of the olefin polymer is 1
5,000 to 200,000, preferably 10,000
It can be selected from a range of about 150,000.

When an olefin polymer is blended in the foamed sheet of the present invention, the ratio (weight ratio) between the cyclic olefin polymer and the olefin polymer is such that cyclic olefin polymer / olefin polymer = 99.9 / 0.1. ５０50/50, preferably 95/5 to 60/40, more preferably 90/1.
It can be selected from the range of about 0 to 70/30.

[Properties of the foamed sheet] The foaming ratio of the foamed sheet is 1.1 to 10 times, preferably about 1.4 to 5 times. When the expansion ratio is 1.1 times or more, heat retention, heat insulation, and appearance are good, and when the expansion ratio is 10 times or less, the stackability of the container formed of the foam sheet is improved, and the container is not bulky.
The foaming ratio is calculated according to the following equation based on the apparent density of a foamed sheet and a non-foamed sheet according to JIS Z1536.

Expansion ratio = apparent density of non-foamed sheet / apparent density of foamed sheet In the direction orthogonal to the sheet extrusion direction, the number of cell membranes per unit thickness is 1 to 50 / mm.
Preferably, it is about 5 to 40 pieces / mm. 1 bubble film
When the number of pieces / mm or more is good, heat retention, heat insulation and appearance are good,
When the number is not more than 50 pieces / mm, the stiffness and impact resistance of the container formed from the foamed sheet are improved. In addition, the number of cell membranes is obtained by collecting ultrathin sections from the width direction of the foam sheet, counting the number of cell membranes observable with an optical microscope in the thickness direction, and converting the number per 1 mm thickness.

The dimensional change rate (Mh) in the sheet flow direction after heat treatment at 130 ° C. for 30 seconds and the dimensional change rate (Th) in the direction perpendicular to the sheet flow direction are ± 10% or less, respectively. Preferably, it is about ± 8% or less.

The dimensional change rate conforms to JIS K6767, and the dimensional change rate (Mh) in the sheet flow direction is obtained by sampling the central part in the width direction of the foamed sheet, setting the dimension before heating to M ₀ , If the dimensions and the M _1, is calculated by the following equation.

Mh = {(M ₀ −M ₁ ) / M ₀ } × 100

The dimensional change (Th) in the direction orthogonal to the sheet flow direction is calculated by the following equation, where T _{0 is} the dimension before heating and T ₁ is the dimension after heating.

Th = {(T ₀ −T ₁ ) / T ₀ } × 100

The thickness of the foam sheet is about 0.1 to 3 mm, preferably about 0.3 to 2 mm. 0.1mm thick
Above, the container formed of this foam sheet has good stiffness and heat insulation, and when it is 3 mm or less, the container has good stacking properties and does not bulk.

[Production Method of Foamed Sheet] The foamed sheet of the present invention is obtained, for example, by melt-kneading the above-mentioned pellets containing the cyclic olefin polymer by an ordinary extruder, and extruding it through a circular die, a T-die or the like. It can be obtained by molding. As the foamed sheet, at least two layers of sheets of the same or different materials may be laminated.

Examples of the foam molding method include a method in which a chemical foaming agent is added and extrusion molding is performed, and a method in which extrusion molding is performed while a foaming gas raw material is injected.

Examples of the chemical foaming agent include hydrogen carbonate such as sodium hydrogencarbonate and ammonium hydrogencarbonate, and azo compounds such as azodicarbonamide and azobisisobutyronitrile. And hydrocarbons such as butane.

The foamed sheet may further contain a coloring agent such as a pigment or a dye, a dispersant such as a higher fatty acid salt, an inorganic filler such as talc, a conductivity-imparting agent, an antistatic agent, or a silicone. Molding agents, anti-fogging agents and the like can be added.

[Method of Manufacturing Container] The container of the present invention can be obtained, for example, by molding the foamed sheet by a conventional molding method, for example, vacuum molding, blow molding, air pressure molding, matched mold molding, or the like.

[0048]

According to the present invention, it is possible to produce a low-foamed plastic sheet excellent in both heat resistance and impact resistance, and also excellent in heat retention, oil resistance and moldability, and a container using the same. Can be.

[0049]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Examples 1 to 5 1 part by weight of mineral oil (WITCO, plastic oil 250) was spread on 100 parts by weight of the polymer or polymer mixture shown in Table 1, and the foaming agent was added to Table 1 And the amounts shown in Table 2. Next, these compositions were supplied to an extruder (diameter 65 mm, L / D = 32), melt-kneaded, extruded from a T-die, foamed, and quenched to obtain a foamed sheet. The number of cell membranes and the dimensional change rate (M
h and Th), expansion ratio, and thickness are shown in Table 1. The abbreviations and details of the components shown in Table 1 are shown below.

Next, using this sheet, a cup-shaped container (opening diameter 90 mm, bottom diameter 70 mm, depth 80 m) by a single-shot vacuum forming machine (manufactured by Asano Laboratory Co., Ltd.)
m) was molded. This container was evaluated for heat resistance, moldability, appearance buckling strength, and impact resistance by the methods described below. Table 1 shows the results.

(Polymer or compounding component) COC (cyclic olefin polymer in which R ¹ and R ² are H in the formula (3)): Zeonor 1420R (manufactured by Zeon Corporation) LDPE (low-density polyethylene): JM906A (Manufactured by Nippon Polyolefin Co., Ltd.), MFR = 21 g / 10 min. HDPE (high density polyethylene): J-LEX HD
KF265A (manufactured by Nippon Polyolefin Co., Ltd.), MFR
= 0.65 g / 10 min Talc: MICRON WHITE # 5000S (manufactured by Hayashi Kasei Co., Ltd.) Blowing agent (mixture of sodium bicarbonate and sodium citrate): Cell Mike 623 (manufactured by Sankyo Kasei Co., Ltd.)

(Heat resistance) 100 g of salad oil (manufactured by Nisshin Oil Co., Ltd.) was placed in a food container, and heated in a microwave oven of 500 W for 5 minutes. The degree of deformation of the container after heating was visually observed and evaluated according to the following criteria.

：: no deformation and no melting marks on the surface Δ: slight deformation or melting marks on the surface X: large deformation and melting marks on the surface

(Formability) The appearance of the bottom surface and the bottom corner of the cup-shaped container was evaluated according to the following criteria.

：: Uniformly stretched and formed to a uniform thickness Δ: Irregularity in bottom or corner thickness ×: Torn in part of bottom or corner

(Heat Insulation) The feeling when holding hot water at 70-80 ° C. in a cup-shaped container and holding the side of the container was evaluated on the basis of the following criteria using 10 adult women as subjects.

○: Can be held without feeling uncomfortable △: Can be held if endured ×: Cannot be held hot

(Impact resistance) 0 to 5
100 ml of water at 0 ° C., the container opening was heat-sealed with a non-foamed film of the same composition, and the container was visually observed from a height of 30 cm when the container was dropped on a concrete floor. evaluated.

：: less than 10% Δ: 10 to 50% ×: more than 50%

[0061]

[Table 1]

Comparative Examples 1 to 5 In Comparative Examples 1 to 4, except that the compositions shown in Table 2 were used, foamed sheets were obtained in the same manner as in Examples 1 to 5, and cup-shaped containers were formed. In Comparative Example 5, a foamed sheet was obtained in the same manner as in Examples 1 to 5, except that the composition shown in Table 2 was extruded at a draft ratio (shown in the following formula) of 3 at the time of extrusion. Was molded. Table 2 shows the results.

Draft ratio = gap of lip opening of T die (mm) / thickness of foam sheet (mm)

[0064]

[Table 2]

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) B32B 27/00 B32B 27/00 H B65D 1/09 C08F 32/00 C08F 32/00 B29K 23:00 // B29K 23: 00 55:00 55:00 105: 04 105: 04 B29L 22:00 B29L 22:00 C08L 45:00 C08L 45:00 B65D 1/00 AB F term (reference) 3E033 AA20 BA14 BB04 BB08 CA03 CA07 CA09 4F074 AA15 BA02 BA03 BA04 BA13 BA14 BA36 BA37 CA22 DA02 DA22 DA24 DA34 4F100 AK02A AK02B AK03A AK03B AK04A AK04B AK05 AK06 AL01A AL01B AL05A AL05B BA02 BA14 CA01 DA01 DJ01A DJ01B GB16 JA06A JA06 Y03 J03 Y03 J03 Y03 J03 Y03 J03 J03 AH52 AP11 AP14 KA01 KA11 4J100 AA02Q AA03Q AA04Q AA07Q AA15Q AA16Q AA19Q AC03Q AC04Q AD02Q AE03Q AE04Q AE41Q AG04Q AJ02R AL03R AR03P AR04P AR05P AR11P AR15P AR21Q AR02P01

Claims (10)

[Claims] 1. A foam sheet containing a homo- or copolymer having a cyclic olefin in the main chain. 2. The cyclic olefin polymer according to the following formula (1)
The foamed sheet according to claim 1, wherein the foamed sheet is at least one selected from polymers represented by (7). Embedded image (Wherein, R ^{1 to} R ⁵ are the same or different and represent a hydrogen atom, a halogen atom, an alkyl group, an acyl group, an ester group or an alkoxyl group, X represents an integer of 0 or more, and Y represents a natural number) 3. The method according to claim 1, wherein the olefin polymer is a cyclic olefin polymer / olefin polymer = 99.9 / 0.1 or more.
The foamed sheet according to claim 1, wherein the foamed sheet is contained in a 50/50 ratio (weight ratio). 4. The foam sheet according to claim 1, wherein the sheet has an expansion ratio of 1.1 to 10 times. 5. The number of cell membranes per unit thickness in the direction orthogonal to the sheet extrusion direction is 1 to 50 / cell.
The foamed sheet according to claim 1, wherein the thickness is in mm. 6. The dimensional change rate (Mh) in the sheet flow direction after heat treatment at 130 ° C. for 30 seconds and the dimensional change rate (Th) in the direction perpendicular to the sheet flow direction are each ± 10% or less. The foamed sheet according to claim 1. 7. The foamed sheet according to claim 1, wherein the sheet has a thickness of 0.1 to 3 mm. 8. The olefin polymer is a polyethylene having a melt flow rate of 0.5 g / 10 minutes or more.
The foam sheet according to the above. 9. The foamed sheet according to claim 1, wherein at least two layers of the same or different materials are laminated. 10. A container formed of the foamed sheet according to claim 1.