JPH0686929U - Non-crosslinked propylene resin laminated foam sheet container - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a container that is thin, has excellent moldability, heat resistance, and heat retention, does not crack the surface of the container, and has sufficient container strength and rigidity at the bottom corners. To do. [Structure] Density 0.04 to 0.4 g / cm ³ , thickness 0.
Non-cross-linked propylene-based resin obtained by laminating a non-cross-linked propylene-based resin foam sheet 2 having a closed cell ratio of 5 to 3 mm and 80% or more, and a resin sheet 3 having a thickness of 200 to 1000 μm and an inorganic filler content of 5 to 70%. Of the laminated foam sheet 4,
A non-crosslinked propylene-based resin laminated foam sheet container 1 formed so that the resin sheet 3 side is the outer surface side.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a laminated foam sheet container, and particularly to a thin non-crosslinked propylene-based resin laminated foam sheet container having sufficient heat retention and strength.

[0002]

[Problems to be solved by conventional techniques and devices]

 BACKGROUND ART Conventionally, a food container or a packaging container, which is composed of a laminated sheet of a polystyrene resin foamed sheet and a resin sheet and has a relatively deep container depth with respect to the diameter of the container opening, has been widely used. However, these containers are insufficient in heat resistance and rigidity, and with the recent spread of microwave oven-heated foods, heat resistance and heat retention as food containers for heating and cooking have been demanded, and they do not take up storage space. In order to reduce the bulk when stacked, the rigidity of the bottom corners of the container is required.

Therefore, in order to improve heat resistance, the base resin of the foamed sheet is a styrene-based resin such as a styrene-maleic anhydride copolymer or a styrene-methacrylic acid copolymer, or a cross-linked propylene-based resin. Is proposed. When a foamed sheet using the above styrene-based resin copolymer as the base resin is used and a conventional resin sheet is laminated on it to form a deep-formed laminated sheet into a container, the amount of comonomer component relative to the styrene component is increased. Although the heat resistance can be improved by doing so, there is a problem that the moldability is deteriorated and defective products such as cracks are formed in the skin layer on the container surface during deep drawing.

Further, when a foamed sheet using a crosslinked propylene-based resin as a base resin is used and a laminated sheet in which a conventional resin sheet is laminated is formed into a container, the resin is crosslinked in the manufacturing process of the foamed sheet. Since the sheet is stretched after being foamed, the sheet is hardly stretched, and it is also difficult to stretch it after foaming, resulting in poor shape retention. Was difficult to obtain, and the tendency was more remarkable especially when the thickness was thin.

Further, a container obtained by molding a sheet having a low independent foaming rate, such as a non-crosslinked propylene resin foam sheet by the T-die method, has poor heat insulation and insufficient heat retention. There was a problem.

Furthermore, it has been impossible to obtain a thin-walled deep-drawing container having sufficient rigidity at the bottom surface of the container by the above-mentioned various means.

[0007]

[Means for Solving the Problems]

 The present invention has been made in order to solve the above-mentioned conventional problems, and it is thin, has excellent moldability, heat resistance, and heat retention, does not crack the surface of the container, and has sufficient strength of the container to ensure that the corners of the bottom surface are Rigidity and the like are intended to provide a particularly excellent container.

That is, the container made of the non-crosslinked propylene-based resin laminated foam sheet of the present invention has a density of 0.04 to 0.4 g / cm ³ , a thickness of 0.5 to ³ mm, and a non-crosslinked polypropylene having a closed cell rate of 80% or more. A resin sheet having a thickness of 200 to 1000 μm and an inorganic filler content of 5 to 70% by weight is laminated on at least one side of a resin foam sheet.

The deep-drawing container described later in the present invention means a container having a ratio of the maximum container depth to the minimum diameter of the container opening of 0.5 or more.

[0010]

【Example】

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The drawings show one embodiment of the present invention. The container 1 made of the non-crosslinked propylene-based resin laminated foam sheet of the present invention has a non-crosslinked propylene-based resin laminated foam sheet 4 formed by laminating a non-crosslinked propylene-based resin foam sheet 2 and a resin sheet 3 as shown in FIG. 1, for example. The resin sheet 3 is formed in a truncated cone shape so that the resin sheet 3 side is the outer surface side. Further, the deep-drawing container has a ratio D / L of the maximum container depth D to the minimum diameter L of the container opening of 0.5 or more.

The density of the non-crosslinked propylene resin foam sheet 2 is 0.04 to 0.4 g / cm ³ . When the density is less than 0.04 g / cm ³ , the shape retention and rigidity are poor, and 0. If it exceeds 4 g / cm ³ , the flexibility and heat retention of the container are low.

The thickness is 0.5 to 3 mm, preferably 0.5 mm to 1.8 mm. If the thickness is less than 0.5 mm, the problem of elongation during heating is likely to occur, which adversely affects the formability. If it exceeds 3 mm, it cannot be said that it is usually thin, and in extreme cases, the height when stacking containers is high. (Generally referred to as "stack height") becomes too high, which makes storage difficult.

Further, the closed cell ratio is 80% or more, and when the closed cell ratio is less than 80%, sufficient heat retention cannot be obtained.

The non-crosslinked propylene-based resin used in the non-crosslinked propylene-based resin foam sheet 2 may be any of a homocopolymer, a block copolymer and a random copolymer, and propylene and a small amount of olefin other than propylene. Copolymers with are preferred. Examples of this olefin include ethylene and α-olefins having 4 to 10 carbon atoms, and these can be used alone or in combination of two or more. Examples of the α-olefin having 4 to 10 carbon atoms include 1-butene, isobutylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene and 3,4-dimethyl-1-. Butene, 1-heptene, 3-methyl-1-hexene and the like can be mentioned.

The above-mentioned olefin is usually contained in the copolymer in an amount of preferably 0.5 to 30% by weight, more preferably 1 to 10% by weight.

Further, as the non-crosslinked propylene-based resin, one having a long-chain branch in the main chain is preferable.

The above-mentioned propylene-based resin having a long-chain branch in the main chain is an ordinary crystalline linear propylene-based resin (usually having a weight average molecular weight of 100,000 or more), in which an atactic component or / and A low-temperature decomposition type (decomposition temperature: room temperature to about 120 ° C) peroxide is mixed with a resin containing a component that is isotactic but not crystallized, and the mixture is heated to 120 ° C or lower to obtain a normal propylene resin. Can be obtained by a method in which an atactic or / and non-crystallizing isotactic component is bonded to the main chain as a branched chain, and usually a branched structure having a long-chain branch at the end of the main chain is mainly formed. I have.

Examples of the low-temperature decomposition type peroxide include di (s-butyl) peroxydicarbonate, bis (2-ethoxy) peroxydicarbonate, dicyclohexylperoxydicarbonate, di-n-propylperoxydicarbonate. Carbonate, di-n-butyl peroxy dicarbonate, diisopropyl peroxy dicarbonate, t-butyl peroxy neodecanoate, t-amyl peroxy neodecanoate, and t-butyl peroxypivalate are exemplified.

Further, as the above-mentioned non-crosslinked propylene-based resin, one having a drawdown property of 60 m / min or less is preferable. What is drawdown property? Molten propylene resin heated to 230 ° C is extruded from a melt indexer nozzle (aperture 2.095 mm, length 8 mm) at a constant speed of 10 mm / min into a string shape, and then the string material is extruded. After passing through the feed roll located above the tension detection pulley located below the nozzle, it is taken up by the take-up roll while gradually increasing the take-up speed of the take-up roll. And the take-up speed of the string-like material at the time of cutting.

In general, there is the following relationship between the number or length of long chain branches and drawdown property. That is, the greater the number of long chain branches and the longer the branch length, the lower the drawdown value. Therefore, by increasing the number and length of long-chain branches, the value of the drawdown property can be decreased secondarily. Therefore, in order to obtain a copolymer exhibiting a desired drawdown value, the reaction conditions are considered in consideration of these so that a non-crosslinked propylene-based resin having an appropriate number and length of long chain branches can be obtained. Just set it.

If the main chain has no branch, or if it has branch but is too short or has a small number of branches, the drawdown property usually exceeds 60 m / min. Even if it is attempted to obtain a foamed sheet having a density of 0.03 to 0.4 g / cm ³ by performing extrusion foaming using such a propylene-based resin, the obtained foamed sheet has many corrugations and surface irregularities. It becomes worthless.

To obtain a non-crosslinked propylene-based resin having a long-chain branch in the main chain and a drawdown property of 60 m / min or less, for example, ordinary propylene (having no long-chain branch in the main chain) is used. While the system resin is stirred in a reactor equipped with a stirrer, the inside of the reactor is replaced with an inert gas such as argon, and then the above-mentioned peroxide is usually added in an amount of 5 to 50 millimoles per 1 kg of the resin and stirred. It is possible to use a method of continuously heating to about 120 ° C., preferably about 70 to 105 ° C. for reaction (usually 30 to 120 minutes), and then stopping the reaction. In stopping the reaction, a method of introducing a reaction terminator such as methyl mercaptan into the reaction vessel or heating the reaction product at about 130 to 150 ° C. for 20 to 40 minutes can be employed.

The non-cross-linked propylene-based resin used for the non-cross-linked propylene-based resin foam sheet 2 also preferably has a half-crystallization time at the crystallization temperature of + 15 ° C. of 800 seconds or longer, and particularly preferably 1000 seconds or longer. Is preferred. A crystallization rate measuring instrument can be used to measure the semi-crystallization time.

To measure the semi-crystallization rate, first, the support holding the film-like sample is placed in the air bath of the crystallization rate measuring instrument to completely melt the sample, and then the molten sample is applied to the support. Each sample is immersed in an oil bath maintained at the crystallization temperature of + 15 ° C so as to block the optical path between the light source and the light sensor, and the light sensor always keeps constant until the molten sample solidifies again. The voltage of the light source is adjusted so that the amount of light is detected, and the voltage-time curve as shown in FIG. 2 is obtained. When the voltage when the voltage in this curve has a constant value is V ₀ , the time until the voltage becomes 1/2 V ₀ is the half-crystallization time.

As a method for obtaining the non-crosslinked propylene resin foam sheet 2, a non-crosslinked propylene resin and a foaming agent are melt-kneaded in an extruder, and then this melt-kneaded product is attached to the tip of the extruder to form an annular lip. It is possible to employ a method in which a circular die having the above is used, extrusion foaming is performed from the lip of the die to obtain a tubular foam, and then the tube is cut open to form a sheet.

As the foaming agent, an inorganic foaming agent, a volatile foaming agent, a decomposable foaming agent, or the like can be used. Examples of the inorganic foaming agent include carbon dioxide, air and nitrogen.

As the volatile blowing agent, aliphatic hydrocarbons such as propane, n-butane, i-butane, pentane and hexane, cycloaliphatic hydrocarbons such as cyclobutane and cyclopentane, trichlorofluoromethane and dichloro are used. Examples thereof include halogenated hydrocarbons such as difluoromethane, dichlorotetrafluoroethane, methyl chloride, ethyl chloride and methylene chloride.

Further, examples of the decomposition type foaming agent include azodicarbonamide, dinitrosopentamethylenetetramine, azobisisobutyronitrile, sodium bicarbonate and the like. These foaming agents can be appropriately mixed and used.

Although the amount of the foaming agent used varies depending on the type of the foaming agent, the desired expansion ratio, etc., the amount of the foaming agent used to obtain the foam sheet 2 having a density of 0.03 to 0.4 g / cm ³ As a guide, about 0.2 to 2.7 parts by weight of inorganic foaming agent (converted to carbon dioxide), about 0.5 to 7 parts by weight of volatile foaming agent (converted to butane), and decomposition type per 100 parts by weight of resin. The foaming agent is about 0.1 to 11 parts by weight. In addition, adjustment of the foamed sheet having a density of 0.04 to 0.4 g / cm ³ and a thickness of 0.5 to ³ mm, which constitutes the container of the present invention, is performed by laminating the foamed sheet before molding the container with a magnification and a thickness by heat. It may decrease after the thermoforming process, so this must be taken into consideration.

If necessary, a bubble control agent can be added to the melt-kneaded product of the resin and the foaming agent when the foamed sheet 2 is manufactured. Examples of the air bubble modifier include inorganic powder such as talc and silica, an acid salt of polyvalent carboxylic acid, a reaction mixture of polyvalent carboxylic acid and sodium carbonate or sodium bicarbonate. It is preferable to add the cell regulator in an amount of 13 parts by weight or less per 100 parts by weight of the resin (except when a large amount of inorganic filler is contained in the resin). Further, if necessary, additives such as a stabilizer, a UV absorber, an antioxidant and a colorant may be added.

Further, an inorganic filler may be contained in the resin in advance to the extent possible. As the inorganic filler, the same ones as those contained in the resin sheet 3 described later can be used. The average particle size of these inorganic fillers is preferably 1 to 70 μm.

In the present invention, since the non-crosslinked propylene resin is used as the base resin of the foamed sheet 2, the moldability and heat resistance are improved as compared with the case where the styrene resin copolymer is used as the base resin. In addition, since the foamed sheet 2 can be stretched, the non-crosslinked propylene-based resin laminated foamed sheet container of the present invention has excellent shape retention and does not easily lose its shape. In addition, a foamed sheet having a density of 0.04 to 0.4 g / cm ³ and an independent bubble ratio of 80% or more and having a good surface state can be obtained, and in particular, the main chain has long chain branches and the drawdown property is 60 m / When the non-cross-linked propylene-based resin of the following amount is used, the above foamed sheet can be easily obtained. Therefore, even if it is thin with a thickness of 0.5 to 3 mm, it is sufficient if it is laminated with the resin sheet 3. It has rigidity, heat resistance and heat retention.

The resin sheet 3 contains the inorganic filler in an amount of 5 to 70% by weight, preferably 15 to 50% by weight, based on the total weight, and the inorganic filler greatly contributes to the improvement of the rigidity of the container 1. Particularly in the case of a deep-drawing container, a remarkable effect is seen. When the content of the inorganic filler is less than 5% by weight, the effect of improving the rigidity is poor, and when it exceeds 70% by weight, the moldability is adversely affected. Examples of the inorganic filler include talc, silica, calcium carbonate, clay, zeolite, alumina, barium sulfate, and glass.

The resin sheet 3 has a thickness of 200 to 1000 μm. When the thickness is less than 200 μm, the shape retention and rigidity are poor, and when the thickness exceeds 1000 μm, the flexibility is low and the workability such as lamination is poor. In the present invention, since the resin sheet 3 contains the inorganic filler, sufficient rigidity can be obtained and heat resistance can be obtained even if the thickness is made as thin as 200 μm at minimum.

As the base resin of the resin sheet 3, polyethylene resin, polypropylene resin, polyester resin, acrylic resin, polyvinyl chloride or the like can be used. In particular, polypropylene resin is preferable from the viewpoints of recyclability, adhesiveness, heat resistance, oil resistance, rigidity and the like, and it is more preferable that it is the same as the resin constituting the foam sheet 2. That is, for example, if the base resin of the foam sheet 2 is a propylene-ethylene block copolymer, the base resin of the resin sheet 3 is also preferably a propylene-ethylene block copolymer.

The non-crosslinked propylene-based resin laminated foam sheet 4 is obtained by laminating and molding the non-crosslinked propylene-based resin foamed sheet and the resin sheet. As a laminating method, a general method such as an extrusion laminating method, a thermal laminating method, or a laminating method with an adhesive such as hot melt can be adopted. However, the resin sheet 3 used in the present invention is a normal one. Since it is thicker, when using the thermal lamination method, consider the closed cell rate, the expansion ratio, and the melt defoaming on the side of the foamed sheet that leads to thickness reduction, so that it does not fall outside the specified range of the present invention. There is a need to do. When a laminating method using an adhesive is adopted, a commonly used adhesive can be used, and an EVA adhesive is particularly preferable.

As the non-crosslinked propylene-based resin laminated foam sheet 4, it is sufficient that the resin sheet 3 is laminated on at least one surface of the non-crosslinked propylene-based resin foamed sheet 2, and the resin sheet 3 is the non-crosslinked propylene-based resin foamed sheet. It may be laminated on both sides of the sheet 2. However, when the resin sheets 3 are laminated on both sides, the resin sheet 3 is thicker than a normal one, and is not so preferable in consideration of the stack height.

In order to mold the non-crosslinked propylene-based resin laminated foam sheet container 1 of the present invention, the above-mentioned non-crosslinked propylene-based resin laminated foam sheet is subjected to vacuum forming, pressure forming, and free drawing forming such as plug forming, plug application, etc. And and ridge molding, ridge molding, matched mold molding, straight molding, drape molding, reverse draw molding, air slip molding, plug assist molding, plug assist reverse draw molding, etc. Mold into a container shape.

When the container 1 is molded using the non-crosslinked propylene-based resin laminated foam sheet in which the resin sheet is laminated on only one surface of the non-crosslinked propylene-based resin foamed sheet as shown in FIG. As described above, the non-crosslinked propylene resin foam sheet 2 side may be the inner surface side of the container, and the resin sheet 3 side may be the outer surface side of the container. either will do.

Next, the present invention will be described in more detail with reference to specific examples. [Examples 1 to 5 and Comparative Examples 1 to 5] The containers of Examples 1 to 5 and Comparative Examples 1 to 5 include a foamed sheet having the following resin A as a base material and a resin B (1, 2) as a base material. An outer diameter shape with a minimum opening diameter of 120 mm and a maximum depth of 70 mm, using a resin laminated foam sheet obtained by laminating Is a thin-walled, deep-conical frustum-shaped container. Tables 1 and 2 also show the moldability when molding the container, the rigidity of the bottom corners of the obtained container, the heat retaining property, the thickness of the foam sheet 2 and the resin sheet 3, and the like.

Resin A: Propylene / ethylene block copolymer having long-chain branch in the main chain (“SD-632” manufactured by Himond USA, Inc .: melting point 159.9 ° C., drawdown property 3.1 m / min, melt tension 13 0.0gf) Resin B1: Propylene homocopolymer ("E120G" manufactured by Nippon Petrochemical Co., Ltd.) 2: The same resin as Resin A

The contents of the evaluation are as follows. A: Very good. ○: Generally good. X: Insufficient.

[0043]

[Table 1]

[0044]

[Table 2]

Since the container of the present invention has excellent rigidity, it is suitable for use in not only food containers but also precision equipment such as cameras, and packaging of electronic parts such as audios and parts thereof.

[0046]

[Effect of device]

As described above, the container made of the non-crosslinked propylene resin laminated foam sheet of the present invention is made of the resin laminated foam sheet in which the resin sheet is laminated on at least one side of the foam sheet, and the non-crosslinked propylene resin is used as the foam sheet. Since it is used as a base resin, the foamed sheet has excellent heat resistance and moldability, and the foamed sheet can be stretched so that it retains good shape when molded into a container. There is. Further, since the foamed sheet has a density of 0.04 to 0.4 g / cm ³ and a closed cell rate of 80% or more, it is made of a non-crosslinked propylene-based resin laminated foamed sheet in which the foamed sheet and the resin sheet are laminated. The container has the advantage of excellent heat retention.

Since the resin sheet contains an inorganic filler in an amount of 5 to 70%, a container made of a non-crosslinked propylene-based resin laminated foam sheet in which the resin sheet is laminated is excellent in deep-drawing moldability and rigidity. There is an advantage that the strength of the corners of the bottom surface is excellent and the heat resistance is higher. It is also possible to reduce the calories burned when the above-mentioned container is incinerated.

The non-crosslinked propylene-based resin laminated foam sheet container is a resin laminated foam in which a foamed sheet having a thickness of 0.5 to 3 mm and a resin sheet having a similar thickness of 200 to 1000 μm are laminated. Since it is made of sheet and is thin as a whole, there is an advantage that the height when stacking containers (stack height) becomes small.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view of a container made of a non-crosslinked propylene resin laminated foam sheet according to the present invention.

FIG. 2 is a voltage-time curve obtained by crystallization rate measurement.

[Explanation of symbols]

 1 Container made of non-crosslinked propylene-based resin laminated foam sheet 2 Non-crosslinked propylene-based resin foamed sheet 3 Resin sheet 4 Non-crosslinked propylene-based resin laminated foam sheet L Minimum diameter of container opening D Maximum container depth

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B65D 1/09

Claims (1)

[Scope of utility model registration request] 1. A non-crosslinked propylene-based resin foam sheet having a density of 0.04 to 0.4 g / cm ³ , a thickness of 0.5 to ³ mm, and a closed cell ratio of 80% or more and a thickness of 200 to at least one surface.
A container made of a non-crosslinked propylene-based resin laminated foam sheet, which comprises resin sheets having a thickness of 1000 μm and an inorganic filler content of 5 to 70% by weight.