JPH09226771A - Partitioning material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a partitioning material having excellent buffering property, excellent flaw preventing property, proper solidity and nerve by providing a first expanded sheet having as a main component a polypropylene resin whose density is within a specified range and layering a second expanded sheet having as a main component a polypropylene resin whose density is lower than that of the first expanded sheet on one face of the first expanded sheet. SOLUTION: A partitioning material 1 which is to be set up into a shape of well crib for storing and moving precision parts comprises a groove 2 which can be fitted in other partitioning material. The partitioning material 1 is formed by layering a second expanded sheet having as a main component a polypropylene resin whose density is within a range of 0.07-0.025g/cm<3> on at least one face of a first expanded sheet having as a main component a polypropylene resin whose density is within a range of 0.5-00.0g/cm<3> . The first expanded sheet has a bending modulus of 100MPa or above at room temperature and the second expanded sheet has a tensional modulus of 30MPa or below. For the polypropylene resin, a polypropylene-polyethylene block copolymer is used.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a partition material.
Since the partitioning material of the present invention is rich in cushioning property and scratch resistance, and further has appropriate hardness and elasticity, it can be used in IC, LSI, CD-RO.
It can be suitably used as a partitioning material for storing, organizing and moving M, precision parts, plated products, plastic products and the like.

[0002]

2. Description of the Related Art
Corrugated paper, polystyrene foam, polyethylene foam, etc. are used as the partition material. However, corrugated cardboard has drawbacks such as poor hygroscopicity and buffering property against repeated use.
On the other hand, polystyrene foam is excellent in rigidity, but is inferior in cushioning property and repeated buffering property. In addition, there is a drawback in that powder is generated when the partition material is cut out, and the powder adheres to a product to reduce its commercial value.

As measures against this, there are a method of mixing a styrene polymer with a rubber component, a method of mixing a polyethylene resin and a polystyrene resin, and the like. However, although the softening is improved, there is a problem that the elastic recovery property and the cushioning performance of the repetition are hardly changed and the solvent resistance is also poor. Particularly, in the case of a mixture of polystyrene and polyethylene, there is a problem that it is difficult to obtain a low-density resin because the compatibility between the resins of both is poor.

Polyethylene foam is excellent in flexibility and cushioning property for repeated use, but is not suitable for partitioning relatively heavy products. As a countermeasure, if the foam density is increased, the flexibility will be impaired. Therefore, polyethylene foam is limited to use in products that are lightweight and require a high degree of cushioning. Further, the crosslinked polyethylene foam having improved mechanical strength and secondary processability by the crosslinking treatment has flexibility and excellent product protection, but lacks shape retention strength. Therefore, there is a problem in that the shape is not easily held when carrying it and it is difficult to hold, and further, the material cannot be recycled due to the gel component used for crosslinking. As the crosslinking treatment method, a method using a chemical crosslinking agent, a method using ionizing radiation, etc., a silane-modified polyethylene-based resin is produced by graft-polymerizing a silane compound onto a polyethylene-based resin, and the resin is treated with a silanol catalyst and water. A so-called water-crosslinking method in which crosslinking is performed in the presence of such a compound is known. However, all the crosslinking methods require extremely complicated steps, and some of them are expensive in equipment, which is very industrially disadvantageous.

As a countermeasure against this, a method in which a flexible polyolefin resin foam is laminated on at least one surface of the styrene resin foam to provide the surface with flexibility and strength (Japanese Utility Model Publication No. 62-18443, actual). Fairness 5-47075
No.). However, due to the difference in softening temperature and moldability of the two resins, the secondary processability is poor, and it is necessary to provide an adhesive layer for lamination with the styrene-based resin, resulting in poor strength and cost disadvantage.

On the other hand, polypropylene resin is superior to polyethylene resin in heat resistance and strength. However, polypropylene resins have extremely low melt viscosity above the crystalline melting point and cannot retain foamed bubbles,
Easy to break. Therefore, the conventional polypropylene-based resin foam can only obtain a foam having an open cell ratio, and it is difficult to obtain a foam having closed cells and excellent mechanical properties and heat resistance. That is, conventional polypropylene-based resin foams have only been obtained as low-foamed products having a density of 0.5 g / cm ³ or more or high-foamed products having a density of 0.03 g / cm ³ or less.

[0007]

Thus, according to the present invention, at least one surface of the first foamed sheet mainly composed of polypropylene resin having a density of 0.5 to 0.07 g / cm ³ is provided. There is provided a partitioning material comprising a second foamed sheet containing a polypropylene resin as a main component and having a density in the range of 0.07 to 0.025 g / cm ³ , which is laminated.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The polypropylene resin that can be used in the present invention is not particularly limited, and commercially available polypropylene resins can be used. A preferred polypropylene resin has a Z average molecular weight Mz of at least 2.0 ×.
10 ⁶ and Mz / Mw is at least 3.0 or more,
And the molecular weight distribution curve by gel permeation chromatograph is a camel-type polypropylene-polyethylene block copolymer or a camel-type polypropylene homopolymer having a shape with an overhang of the curve indicating that the polymer contains a branched polymer in the high molecular region. An example is coalescence.

In the present invention, the Z-average molecular weight Mz is the average molecular weight by which the distribution on the highest molecular weight side is emphasized as measured by gel permeation chromatography (hereinafter referred to as GPC), and is the average of the cube of the molecular weights. Means a value. The weight average molecular weight Mw is an average molecular weight obtained by GPC measurement when the measured physical property is directly related to the weight of the polymer, and means an average value of the square of the molecular weight.

The GPC measuring method used in the present invention is as follows. Measuring device: GPC 150-C type (manufactured by Water Co.) Measuring condition: Two columns KF-80M (manufactured by SHODEX Co.) Column temperature 145 ° C. Injection temperature 145 ° C. Pump temperature 60 ° C. Sensitivity 32 Solvent used o-dichlorobenzene (1 0.0 ml / min) Scanning time 50 minutes Injection volume 400 μl Further, the polypropylene resin that can be preferably used in the present invention has a camel-type molecular weight distribution curve. The camel-type molecular weight distribution curve means, for example, a molecular weight distribution curve having a shape having an overhang like a camel spine in a high molecular weight region as shown in FIG. The molecular weight distribution curve shows that certain components in the high molecular weight region have many branches. In addition, in FIG. 1, a curve A indicates a camel-type polypropylene resin that can be used in the present invention,
Curve B shows a polypropylene-based resin in which it is difficult to obtain a sufficient melt tension during foaming.

Here, Mz is less than 2.0 × 10 ⁶ or Mz
When z / Mw is less than 3.0, it is difficult to obtain a sufficient melt tension during foaming, and it is difficult to obtain a partition material having a desired density. Particularly preferably, the resin forming the first foamed sheet is mainly composed of a polypropylene homopolymer showing a camel type in the molecular weight distribution, and the resin forming the second foamed sheet is a polypropylene showing a camel type in the molecular weight distribution. -To be a polyethylene block copolymer. The content of polyethylene in the polypropylene-polyethylene block copolymer is 0.1 to 10% by weight, preferably 1 to 6% by weight.

The camel type polypropylene resin which can be used in the present invention is PF-814, SD-6 manufactured by Highmont Co.
32, X-10005, X11277-22-1 and the like. The camel type polypropylene resin is
In general, those produced by irradiating a conventional linear polypropylene resin with a low level of radiation, or by mixing a small amount of a peroxide to form a branched polymer can also be used.

The partitioning material of the present invention contains the above polypropylene-based resin as a main component, and the main component here means that the content is 60% by weight or more, preferably 80 to 100% by weight. Here, if it is less than 60% by weight, the foamability is impaired, which is not preferable.

In the partitioning material of the present invention, the first foam sheet has a bending elastic modulus of 100 MPa or more at room temperature, and the second foam sheet has a tensile elastic modulus of 30 MPa or less at room temperature. More preferable. Here, the bending elastic modulus of the first foam sheet at room temperature is 100MP.
If it is smaller than a, the strength becomes insufficient, and problems such as a collapse of the shape occur when the product is used for heavy goods. On the other hand, the tensile modulus of elasticity of the second foam sheet at room temperature is 30.
If it exceeds MPa, the cushioning property is poor and problems such as scratches on the surface of the product occur.

Other resins may be added to the polypropylene resin used in the present invention as long as the purpose thereof is not impaired. Resins that can be added include ethylene / propylene random copolymer resins, ethylene / butene /
Examples thereof include propylene copolymer resin, ionomer, ethylene / propylene rubber, and polyethylene resin. Of these, linear low density and ultra low density polyethylene are preferable.

The reason why the first and second sheets are all made of foam is that another method of providing strength is lamination with a non-foamed sheet, but the non-foamed sheet and the foamed sheet were compared. In this case, in order to obtain the same strength, the case where the foamed sheets are laminated can be made lighter and more advantageous in terms of cost. Further, the partitioning material of the present invention, extrusion foaming,
It can be produced by combining compression foaming, injection foaming and the like with a method such as block molding, plate molding, molding. Below, the manufacturing method using extrusion foam molding is demonstrated.

First, a base resin made of polypropylene resin is supplied to a foaming extruder. As the foaming extruder, any device equipped with a die such as a slit die or a circular die generally used in the art can be used. A foaming agent is added to the base resin. The foaming agent is not particularly limited, and a decomposable foaming agent, a gas or volatile foaming agent, or a mixture thereof can be used.
If a polypropylene resin showing a camel type is used as the base resin, the melt viscosity at the time of molding is higher than that of other base resins, so even if a gas or a volatile foaming agent is used, sufficient characteristics are obtained. It is possible to manufacture a partitioning material having the same.

Examples of the decomposable foaming agent include inorganic decomposing foaming agents such as ammonium carbonate, sodium bicarbonate, ammonium bicarbonate, ammonium nitrite, calcium azide, sodium azide and sodium borohydride, azodicarbonamide, azobis. Azo compounds such as sulforamide, azobisisobutyronitrile and diazoaminobenzene, nitroso compounds such as N, N'-dinitrosopentanemethylenetetramine and N, N'-dimethyl-N, N'-dinitrosoterephthalamide , Benzenesulfonyl hydrazide, p-toluenesulfonyl hydrazide and p, p′-oxybisbenzenesulfonyl semicarbazide, p-toluenesulfonyl semicarbazide, trihydrazinotriazine, barium azodicarboxylate and the like. These blowing agents may be used alone or in combination. Further, the addition ratio of the decomposable foaming agent is preferably 0.1 to 5 parts by weight based on 100 parts by weight of the base resin. Further, in order to adjust the decomposition temperature, the amount of generated gas, and the decomposition rate, a known foaming aid can be added.

Examples of the gas blowing agent include air, nitrogen, carbon dioxide gas, propane, neopentane, methyl ether, chlorodifluoromethane, n-butane and i-butane. Here, the gas means that it is a gas at room temperature. On the other hand, examples of the volatile foaming agent include ether, petroleum ether, acetone, pentane, hexane, isohexane, heptane, isoheptane, benzene, and toluene. The addition ratio of the gas or the volatile foaming agent varies depending on the kind of the foaming agent, the desired expansion ratio, etc.,
It is preferably 0.5 to 20 parts by weight with respect to 100 parts by weight of the base resin.

Of the above foaming agents, butane and nitrogen are particularly preferable. Use of these foaming agents can reduce the influence on the environment (such as destruction of the ozone layer). In the present invention, a cell regulator may be further added during melt-kneading of the resin and the foaming agent. Examples of the foam control agent include inorganic powders such as talc and silica, acidic salts of polycarboxylic acids, and reaction mixtures of polycarboxylic acids with sodium carbonate or sodium bicarbonate. The amount of the cell regulator is preferably 0.01 to 1.0 part by weight with respect to 100 parts by weight of the base resin. Furthermore, if necessary, a heat stabilizer, an ultraviolet absorber, an antioxidant, a colorant, an antistatic agent and the like can be added.

The conditions of the extrusion foam molding are as follows: The resin is melted by heating it at 180 to 240 ° C. in an extruder, and then the die is most suitable for foaming, that is, 140 to 240 ° C.
Preference is given to pouring at 175 ° C. and then extruding. Next, as a method of laminating the foamed sheets, a method of extruding and laminating a new foamed sheet on a preformed foamed sheet, a method of heating and laminating preformed foamed sheets, and a coextrusion method. Any of known methods such as heat fusion such as simultaneous integral molding, a method of laminating with an adhesive, a pressure sensitive adhesive or the like interposed therebetween, or a combination thereof can be used. However, from the viewpoint of increasing the adhesive strength in order to prevent peeling and the like, it is preferable to laminate by heat fusion.

The partition material of the present invention has a thickness of 1.0 to
5.0 mm is preferable. A partitioning material having a thickness of less than 1.0 mm is too soft and is inferior in shape retention, and a partitioning material having a thickness of more than 5.0 mm is difficult to form by thermoforming or the like. Further, the thickness of the first foam sheet is preferably 1.0 to 3.0 mm, and the thickness of the second foam sheet is preferably 1.5 to 4.0 mm.

In the above description, the case of two layers is described, but a partitioning member having a three-layer structure in which the second foam sheet is laminated on both sides of the first foam sheet, and further a laminated body of more layers Is also possible. Particularly, the three-layer structure is preferable. Further, a non-woven fabric, a metal foil, a decorative paper, a printing film, etc. may be laminated on the surface of the laminate of the present invention for the sake of surface beauty and the like, as long as it does not hinder the cushioning properties and mechanical properties of the present invention.

The above partition material can be processed into a desired shape by processing methods such as punching, cutting, and thermoforming. The shape is not particularly limited. For example, as shown in FIG. 2, a groove having a desired width that can be fitted with another partition member at a desired position is formed by the above-described processing, and the partition as shown in FIG. 3 is formed by fitting the groove. You can 2 and 3, 1 indicates a partition member and 2 indicates a groove.

[0025]

EXAMPLES The present invention will be described in more detail below with reference to examples. Example 1 First, a base resin was mixed with a fixed amount of a foaming agent, and the mixture was fed to a foaming extruder equipped with a single screw having a diameter of φ90-φ115 mm. Butane was injected as the blowing agent in the central zone of the first extruder. After being melt-kneaded by the first extruder, the resin was conveyed to the second extruder and poured into a die having a diameter of 90 mm and kept at a temperature most suitable for foaming. Then
It was extruded from a slit having a die gap of 0.5 mm to obtain a tubular foam. Further, it was taken along with a sizing drum having an outer diameter of 380 mm, and cut at one point on the circumference with a cutter to obtain a first foamed sheet. A second foamed sheet was obtained using the same method. Then, the second foam sheet was fused on both surfaces of the first foam sheet by the heat lamination method to obtain a partition member.

The first 2.5 mm-thick used in this embodiment
Foam sheet (Neomicrolen S, Sekisui Plastics Co., Ltd.) and the second foam sheet 1.0 mm thick (Neomicrolen S)
H, manufactured by Sekisui Plastics Co., Ltd.) is shown in Table 1. In addition,
In Table 1 below, the tensile elastic modulus and bending elastic modulus were measured using Tensilon UCT-105 (manufactured by Orientec Co., Ltd.) according to JIS K-6767 and JIS K-7221, respectively.
It measured according to.

[0027]

[Table 1]

The obtained partition material was subjected to thermal conductivity, tensile test, tear test, bending test, dimensional change rate and compression test as follows, and the results are shown in Tables 2-5. (1) Thermal conductivity It was measured according to JIS A 1412. (2) Tensile test According to JIS K 6301 Dumbbell No. 3, a test speed was 50 mm / min, a test temperature was room temperature and 0 ° C., and a test piece leaving time was 3 minutes. (3) Tear test According to JIS K 6301 Dumbbell No. B type, the test speed was 50 mm / min, the test temperature was room temperature and 0 ° C., and the test piece leaving time was 3 minutes. (4) Bending test The test temperature was 50 mm / min, the test temperature was room temperature and 0 ° C., and the test piece was allowed to stand for 3 minutes. (5) Dimensional change rate 150 mm × 150 mm × 4.5 mm was used as a test piece, and the test temperature was measured at 0 ° C., room temperature and 50 ° C. (6) Compression test (compressibility, residual strain, permanent strain) In accordance with ASTM D 1667, dimensions of two partition materials stacked as test pieces 50 mm x 50 mm x 10 mm
Those (including measurement error) were used. The test was conducted as follows. That is, the initial thickness is set to T ₀ , and a predetermined load (0.
25t, 0.75t, 1.25t, 2.5t) at a test speed of 5 mm / min, and the thickness at that time is T
_Set to ₁ . Immediately remove the load and change the thickness to T
_{Assume 2} . The thickness 24 hours after the load is removed is T ₃ .

It was calculated by the following equation using T _{0 to} T ₃ . Compressibility (%) = (T ₀ −T ₁ ) / T ₀ × 100 Residual strain (%) = (T ₀ −T ₂ ) / T ₀ × 100 Permanent strain (%) = (T ₀ −T ₃ ) / T ₀ × 100

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

[Table 4]

[0033]

[Table 5] In the above table, MD indicates the vertical direction and TD indicates the horizontal direction.

[0034]

The partitioning material of the present invention has a density of 0.5 to 0.0.
Composed mainly of polypropylene resin in the first range of density 0.07~0.025g / cm ³ on at least one surface of the foam sheet mainly composed of polypropylene resin in the range of 7 g / cm ³ Since the second foamed sheet is laminated, a partition material excellent in both flexibility and mechanical strength can be obtained with a single resin. Moreover, the partitioning material of the present invention is excellent in heat resistance, oil resistance, and chemical resistance, and is useful in terms of recycling because it uses a single resin.
Furthermore, the partition can be easily formed by forming a groove having a desired width that can be fitted with another partition at a desired position of the partition.

Further, the first foamed sheet has a flexural modulus of 100 MPa or more at room temperature, and the second foamed sheet has a tensile modulus of 30 MPa or less at room temperature. A partition material with excellent strength can be obtained. Further, the polypropylene resin has a Z-average molecular weight Mz of at least 2.0 × 10 ⁶ and Mz / Mw (weight-average molecular weight) of at least 3.0, and a molecular weight distribution curve by gel permeation chromatography. Is a camel-type polypropylene-polyethylene block copolymer or polypropylene homopolymer that is a camel-type having a shape with a curved protrusion indicating that it contains a branched polymer in the polymer region, thereby impairing moldability. It is possible to obtain a partitioning material having flexibility and shape retention.

Further, when the grid-like partition as shown in FIG. 3 is assembled, it is possible to carry it in a state in which it is compressed in a diagonal direction during transportation to reduce the bulk. If the force is released at the time of use, the original state as shown in FIG. 3 can be immediately restored. This is due to the good fin property of the polypropylene resin used for the partitioning material of the present invention. Furthermore, since the first and second foamed sheets are bonded by heat fusion, they have excellent adhesive strength, and even if they are peeled off, the bonded portion is not exposed.

[Brief description of drawings]

FIG. 1 is a graph showing a molecular weight distribution curve of a camel polypropylene resin and a conventional polypropylene resin measured by high temperature GPC.

FIG. 2 is a schematic view of a partitioning material of the present invention.

FIG. 3 is a schematic perspective view of the partition member of the present invention assembled.

[Explanation of symbols] 1 partition material 2 grooves

Claims (5)

[Claims] 1. A density of 0.07 to 0.025 on at least one surface of a first foamed sheet containing a polypropylene resin as a main component and having a density of 0.5 to 0.07 g / cm ^3.
A partitioning material, characterized in that a second foamed sheet containing a polypropylene-based resin as a main component in a range of g / cm ³ is laminated. 2. The partition member according to claim 1, wherein the partition member has a groove having a desired width which can be fitted with another partition member at a desired position. 3. The first foam sheet has a thickness of 10 at room temperature.
The partition material according to claim 1 or 2, which has a bending elastic modulus of 0 MPa or more, and the second foam sheet has a tensile elastic modulus of 30 MPa or less at room temperature. 4. The polypropylene resin in the first and second foamed sheets has a Z-average molecular weight Mz of at least 2.0 × 10 ⁶ and Mz / Mw of at least 3.0.
A polypropylene-polyethylene block copolymer having a (weight average molecular weight) and a camel-shaped polypropylene-polyethylene block having a shape in which the molecular weight distribution curve by gel permeation chromatography shows a curve indicating that the polymer contains a branched polymer in the high molecular region. The partition material according to any one of claims 1 to 3, which is a polypropylene homopolymer that is a united or camel type. 5. The partition material according to claim 1, wherein the first and second foam sheets are bonded by heat fusion.