JP5739847B2 - Polypropylene resin foam sheet, method for producing the same, and partition plate - Google Patents

Description

  The present invention relates to a polypropylene resin foam sheet, a method for producing the same, and a partition plate, and more particularly to a polypropylene resin foam sheet suitable for a partition plate for a packaging box, a method for producing the same, and a partition plate.

The partition plate for packing is required to have rigidity enough to be self-supporting as a partition and softness of the surface so as not to damage an article to be stored. For this purpose, conventionally, a sheet in which a soft foam is laminated on the surface of a hard foam has been used. For example, in Patent Document 1, a plate-shaped uncrosslinked polypropylene resin foam having a density of 0.06 to 0.3 g / cm ³ and a thickness of 1 to 7 mm and at least one surface of the uncrosslinked polypropylene resin foam were laminated. A polypropylene-based resin foam laminate is proposed, which comprises a flexible polyolefin-based resin foam sheet having a thickness of 0.3 to 3.0 mm.

A sheet (for example, refer to Patent Documents 1 and 2) in which a soft sheet is bonded to a rigid foamed sheet needs to be bonded later, which increases the cost of equipment for that and increases the number of processes. It was a factor of the drop in the yield.
In Patent Documents 3 and 4, the foamed sheet is manufactured by extruding it from a perforated die. However, although the foamed sheet having high rigidity can be made by the described method, the softness of the surface is not always obtained. There wasn't.
Patent Document 5 proposes a method of obtaining a high foaming ratio by defining the loss tangent of the resin, but sufficient rigidity of the sheet is not always obtained only by this loss tangent.

Japanese Patent Laid-Open No. 10-024540 Japanese Patent Laid-Open No. 9-226771 JP 2007-204590 A JP 60-085920 A JP 2009-029900 A

  An object of the present invention is to provide a polypropylene resin foam sheet having rigidity and a soft surface, a method for producing the same, and a partition plate.

In view of the above problems, the present inventors have conducted intensive studies, and as a result, found that the ethylene component content in the polypropylene resin, the loss tangent and the bulk density of the polypropylene resin are important, and further studies were made. The present invention has been completed.
That is, the said subject was achieved by the following means.
(1) consists of a single layer sheet extruded from the porous die, the resin component is a non-crosslinked polypropylene resin also meets any of the following (a) ~ (c), and one of the sheet in the MD and TD A polypropylene-based resin foam sheet characterized by having a bending elastic modulus in the direction of 50 MPa or more .
(A) The amount of ethylene component in the non-crosslinked polypropylene resin is 10 to 20% by mass.
(B) Loss tangent of uncrosslinked polypropylene resin at 190 ° C. and 0.02 rad / s is 0.8 to 2.0.
(C) Bulk density is 0.06 to 0.12 g / cm ³
(2) The polypropylene resin foam sheet according to (1), wherein the average cell diameter is 200 μm or less.
(3) Polypropylene-based resin foam sheet according to spring C type surface hardness measured by rubber hardness meter is equal to or Ru der 60 or less (1) or (2).
(4) The polypropylene resin foam sheet according to any one of (1) to (3), wherein the non-crosslinked polypropylene resin is a mixed resin of a homopolypropylene resin and an ethylene resin.
( 5 ) A partition plate comprising the polypropylene resin foam sheet according to any one of (1) to ( 4 ).
(6) The method of producing a foamed polypropylene resin sheet comprising a single layer sheet of uncrosslinked polypropylene resin, Ri is 10-20% by mass ethylene component content in the (a) inorganic crosslinked polypropylene resin, (b ) A non-crosslinked polypropylene resin having a loss tangent of 0.8 to 2.0 at 190 ° C. and 0.02 rad / s of the non-crosslinked polypropylene resin was subjected to an extrusion foaming method using a perforated die, and (c) a bulk density of 0.1. A method for producing a polypropylene-based resin foam sheet, which is 06 to 0.12 g / cm ³ , and the bending elastic modulus in either of MD and TD of the sheet is 50 MPa or more .
( 7 ) The method for producing a polypropylene resin foam sheet according to ( 6 ), wherein an average cell diameter is 200 μm or less.
(8) spring-type C-type surface hardness measured by rubber hardness meter is equal to or Ru der 60 or less (6) or (7) a foamed polypropylene resin sheet manufacturing method according to.
(9) The production of the polypropylene resin foam sheet according to any one of (6) to (8), wherein the non-crosslinked polypropylene resin is a mixed resin of a homopolypropylene resin and an ethylene resin. Method.

According to the present invention, it is possible to obtain a polypropylene resin foam sheet suitable as a partition material having both rigidity and surface softness, a manufacturing method thereof, and a partition plate.
In particular, by extruding from a perforated die, the expansion ratio and the thickness of the sheet can be easily increased, and the rigidity of the sheet is reduced because of the thin unfoamed layer on the surface of each stick-shaped foam. Can be increased.

It is a schematic diagram which shows preferable embodiment of the manufacturing apparatus of the polypropylene resin foam sheet which concerns on this invention.

Hereinafter, embodiments of the present invention will be described in detail.
<< Polypropylene-based resin foam sheet >>
The polypropylene resin foam sheet of the present invention is a single-layer sheet extruded from a perforated die, the resin component is a non-crosslinked polypropylene resin, and satisfies any of the following (a) to (c).
(A) The amount of ethylene component in the non-crosslinked polypropylene resin is 10 to 20% by mass.
(B) Loss tangent of uncrosslinked polypropylene resin at 190 ° C. and 0.02 rad / s is 0.8 to 2.0.
(C) Bulk density is 0.06 to 0.12 g / cm ³
The thickness of the sheet of the present invention is not particularly limited, but is preferably 0.8 to 30 mm, more preferably 1.0 to 20 mm, and most preferably 3 to 10 mm.

<Polypropylene resin composition>
In the present invention, a polypropylene resin is used as the resin component. Here, the polypropylene resin is a resin containing at least 50% by mass of a propylene component in the entire resin component.
Examples of the polypropylene-based resin include not only a resin containing propylene as a monomer component alone, but also a resin using propylene as a monomer component and a resin having no propylene component, for example, a homopolyethylene resin. However, in the case of such combined use, the polypropylene resin in the present invention is 50% by mass or more of the propylene component as a whole resin.
The polypropylene resin is non-crosslinked. That is, the resin used and the resin constituting the produced resin foam sheet contain a crosslinking agent or are subjected to a crosslinking treatment and are not crosslinked.

Examples of the polypropylene resin include homopolypropylene and a propylene copolymer, and examples of the copolymer component include ethylene and α-olefin.
Examples of the α-olefin include ethylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene and the like.
Here, in the present invention, in order to obtain the softness of the surface of the foam sheet, it is necessary to soften the polypropylene resin and to foam the polypropylene resin to a predetermined density.

For this reason, as the polypropylene resin component in the resin composition, propylene-ethylene copolymer containing ethylene component in propylene, or resin having a repeating unit obtained from ethylene other than propylene-ethylene copolymer is used. It is preferable to use together. In particular, it is preferable to use a polypropylene homopolymer in combination with a polyolefin resin other than a propylene copolymer or polypropylene (for example, an ethylene resin, a styrene resin, a (meth) acrylic resin, vinyl acetate, etc.).
Of these, polypropylene homopolymer blended with ethylene resin such as polyethylene and ethylene propylene rubber, propylene-ethylene block copolymer, and propylene-ethylene random copolymer are preferable. In this case, the polypropylene homopolymer is preferably 70 to 90% by mass in the resin component.

  In this invention, the amount of ethylene components in a polypropylene resin is 10-20 mass%. When this content is less than 10% by mass, the surface softness is inferior, and when it exceeds 20% by mass, the rigidity of the resin foam sheet is inferior. The amount of ethylene component in the polypropylene resin is preferably 15 to 20% by mass.

The loss tangent of the polypropylene resin used in the present invention at a temperature of 190 ° C. and a frequency of 0.02 rad / s is 0.8 to 2.0. By using such a resin, appropriate foamability of the foam sheet can be ensured.
If the loss tangent is less than 0.5, the resin is too hard and the expansion ratio cannot be increased. If the loss tangent is greater than 2.0, the resin tends to break when foaming. As a result, the expansion ratio is hardly increased.

The loss tangent can be measured with a viscoelasticity test apparatus (for example, an ARES viscoelasticity test apparatus manufactured by TA Instruments). The specific measurement method is as follows.
First, the resin to be measured is allowed to stand between two parallel plates having a diameter of 25 mm, and after the resin is melted at a predetermined temperature, the plate gap is set to 2 mm. The temperature is set at four levels of 175, 190, 210 and 230 ° C. Next, a strain of 5.0% is applied at a frequency of 0.3 to 100 rad / s (only at 230 ° C., 0.05 to 100 rad / s) and tan δ is measured. The obtained tan δ values are superposed around 190 ° C. according to the temperature-time conversion rule, and the loss tangent at 0.02 rad / s can be finally obtained.

  The resin component is preferably 95 to 99.9 parts by mass with respect to 100 parts by mass of the total solid content of the polypropylene resin composition.

  In the polypropylene resin composition, in addition to the above resin components, foaming agents, cell nucleating agents, heat stabilizers, processing aids, lubricants, impact modifiers, fillers, antioxidants, UV absorption as necessary Agents, light stabilizers, pigments and the like may be added as appropriate.

<Foaming agent>
Examples of the blowing agent include gaseous blowing agents (for example, organic compounds such as carbon dioxide, air, nitrogen, propane), decomposable blowing agents (for example, carbonates, bicarbonates, nitrites, azides, azo compounds, nitro compounds) Elemental compounds, hydrazides, and semicarbazides) are known, and in the present invention, gaseous blowing agents are preferred.
Of these, carbon dioxide is preferably used as the foaming agent. This provides the advantage that the foam production apparatus can be operated safely without the risk of explosion.

In the present invention, a filler may be used.
As fillers, talc, calcium carbonate, clay, kaolin, mica, magnesium oxide, zinc oxide, carbon black, glass, quartz, silica, alumina, nobaculite, hydrated alumina, iron, iron oxide, silicon dioxide, titanium oxide, etc. Is mentioned. Of these, talc is preferable.
When using a filler, 0.01-5.0 mass parts is preferable with respect to 100 mass parts of total solid content of a polypropylene resin composition.

  The average cell diameter is preferably 200 μm or less. If it exceeds 200 μm, not only the rigidity of the foam sheet is inferior but also the surface smoothness may be inferior. The average cell diameter is more preferably 150 μm or less, and even more preferably 100 μm or less. The lower limit of the average cell diameter is preferably 50 μm or more, and more preferably 100 μm or more.

In the present invention, the polypropylene resin foam sheet has a bulk density of 0.06 to 0.12 g / cm ³ . If it is less than 0.06 g / cm ³ , it becomes difficult to maintain rigidity, and if it exceeds 0.12 g / cm ³ , the surface is inferior in softness. The bulk density of the foamed sheet is more preferably 0.09 to 0.12 g / cm ³ .

  The bulk density of the foamed sheet can be determined by an underwater substitution method (JISK7112). The mass of the foam can be measured with an electronic balance (for example, an electronic balance AG204 manufactured by Mettradred).

The rigidity of the polypropylene-based resin foam sheet of the present invention is desirably high for both MD and TD, but one having high rigidity of either MD or TD is preferable.
In the present invention, the stiffness is 50MPa or more flexural modulus. Although an upper limit is not specifically limited, 1000 Mpa or less is preferable.
The flexural modulus can be measured by the method of JISK7221-2 (2006).

The surface hardness of the polypropylene resin foam sheet of the present invention is preferably 60 or less. Although a minimum is not specifically limited, 10 or more are preferable.
The surface hardness is a value measured with a spring-type C-type rubber hardness meter (for example, Asker rubber hardness meter C-type).

<< Method for Producing Polypropylene Resin Foam Sheet >>
In the present invention, a single-layer foamed sheet is produced using the non-crosslinked polypropylene resin composition. Specifically, (a) the amount of ethylene component in the non-crosslinked polypropylene resin is 10 to 20 masses. %, And (b) a non-crosslinked polypropylene resin having a loss tangent at 190 ° C. and 0.02 rad / s of 0.8 to 2.0 of the non-crosslinked polypropylene resin by an extrusion foaming method using a porous die, (C) It is a manufacturing method which makes a bulk density 0.06-0.12g / cm < ³ >.

The polypropylene resin foam sheet can be manufactured by a tandem extrusion system. For example, the apparatus shown in FIG. 1 is used as a manufacturing apparatus used in this system.
FIG. 1 is a schematic view of an example of the production apparatus, and an extruder 1 is provided with a hopper 2, a gas supply port 3, and a die 4. Here, a gas flow rate control device 4 is connected to the gas supply port 3 through a gas supply pipe, and further connected to a carbon dioxide gas cylinder 5 connected to the gas supply pipe.
The extruder 1 has a role of completely melting the polypropylene resin composition and uniformly dispersing the gas in the resin. The extruder 1 may be a single-screw extruder alone, but in order to sufficiently cool the resin at the die outlet, it is desirable to use a tandem extruder in which two extruders are connected in series. The L / D of the extruder (first-stage extruder in the case of a tandem extruder) is desirably 30 or more.

  Next, although an example of the manufacturing method of the polypropylene resin foam sheet concerning this invention is shown with reference to FIG. 1, the manufacturing method of this invention foam is not reduced to this. First, a dry blended resin and additive mixture (hereinafter simply referred to as resin) is supplied to the hopper 2 of the extruder 1. The resin advances while melting in the barrel of the extruder 1 as the screw in the extruder 1 rotates. On the other hand, in a gas supply port 3 installed in the middle of the barrel of the extruder 1, a predetermined amount of carbon dioxide gas controlled by the gas flow rate control device 4 is supplied to the extruder 1 from the gas supply pipe. The molten resin and gas come into contact with each other at the gas supply port 3, and the gas is dissolved in the resin by the high pressure in the extruder 1. The mixture of resin and gas homogeneously mixed in the extruder 1 is extruded from the die 6 and foamed at the same time. In this way, the foam 7 can be obtained.

Here, the cylinder temperature of the first stage extruder is preferably 190 to 230 ° C, and the cylinder temperature of the second stage extruder is preferably 160 to 180 ° C.
The die temperature is preferably 160 to 180 ° C.

  Carbon dioxide gas is preferable as the foaming agent, but the supply amount of the foaming agent from the gas supply valve is preferably 1 to 10% by mass in the first stage extruder with respect to the extrusion amount.

  In particular, when extruded from a perforated die as in the present invention, the rigidity of the foam sheet is particularly strong in the longitudinal direction of the rod-shaped foam, but also the adhesion between the rod-shaped foams in the direction perpendicular to the longitudinal direction of the foam sheet. It can be strengthened by increasing it. As a method for improving the adhesion between rod-shaped foams, there is a method of slightly heating the surface of the rod-shaped foam extruded from a die with a drier or the like and then supplying it to a sizing molding machine.

<< Partition plate >>
In this invention, the said polypropylene resin foam sheet can be preferably used as board | plate materials, such as a partition plate, a curing sheet, and a box main body.
In the present invention, it is preferably used as a partition plate. For example, it can be preferably applied to the partition plates described in JP-A-8-231745 and JP-A-10-24540.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to this.

Example 1
A tandem extrusion system was used as the extruder. A φ65 mm single screw extruder was used as the first stage extruder of the tandem extrusion system, and a φ90 mm single screw extruder was used as the second stage extruder. As the die, a porous die having a width of 400 mm in which 80 holes having a circular cross section with a diameter of 1 mm were arranged in a line at intervals of 5 mm was used. Polypropylene (manufactured by Nippon Polypropylene Co., Ltd .: EA9, MFR = 0.5 g / 10 min (230 ° C .; 2.16 kgf), density 0.9 g / cm ³ ) 84 mass% and high density polyethylene (manufactured by Nippon Polyethylene Co., Ltd .: HY430, A foam sheet molding material comprising MFR = 0.8 g / 10 min (190 ° C .; 2.16 kgf), density 0.956 g / cm ³ ) 15% by mass and talc (manufactured by Nippon Talc Co., Ltd .: Talc MG) 1% by mass. Prepared. Further, the cylinder temperature of the first stage extruder of the tandem extrusion system was set to 170 ° C. to 220 ° C., the set temperature of the second stage extruder was set to 175 ° C. to 220 ° C., and the die temperature was set to 168 ° C.

  The foam sheet molding material was supplied to a first-stage extruder, and a foam sheet having a structure in which a plurality of rod-shaped foams were bundled from a porous die was extruded. At this time, the blowing agent was supplied from the gas supply valve provided on the side surface of the first stage extruder at a rate of 3% by mass with respect to the extrusion amount. The gas concentration was calculated as a value obtained by dividing the gas flow rate [g / min] measured by the mass flow meter by the discharge amount [g / min] and multiplying by 100. For measurement of the gas flow rate, D006H-SS-200 manufactured by Oval was used.

The obtained foam sheet was formed into a smooth surface with a sizing roll, and cut with a cutter to a length of 1000 mm. Thereby, a polypropylene resin foam sheet having a thickness of 5 mm having a structure in which a plurality of rod-shaped foams having a density of 0.06 g / cm ³ was bundled was obtained. The surface hardness of the obtained foamed sheet was 30, and the flexural modulus in the MD direction was 60 MPa.

− Loss tangent measurement −
The loss tangent was measured using an ARES viscoelasticity test apparatus manufactured by TA Instruments. The measurement method is as follows. First, the resin to be measured was allowed to stand between two parallel plates having a diameter of 25 mm, the resin was melted at a predetermined temperature, and the gap between the plates was set to 2 mm. As the temperature, four levels of 175 ° C., 190 ° C., 210 ° C., and 230 ° C. were used. Next, 5.0% strain was applied at a frequency of 0.3 to 100 rad / s (only at 230 ° C., 0.05 to 100 rad / s), and tan δ was measured. The obtained tan δ values were superposed around 190 ° C. according to the temperature-time conversion rule, and the loss tangent at 0.02 rad / s was finally obtained.

− Measurement of bulk density of foam sheet −
The density of the foamed sheet was determined by an underwater substitution method (JISK7112). For measurement of the mass of the foam, an electronic balance AG204 made by Metradred was used.

− Measurement of surface hardness of foam sheet −
The surface hardness of the foamed sheet was measured using an Asker rubber hardness meter C type manufactured by Kobunshi Keiki Co., Ltd. according to the method of Appendix 2 of JIS K 7312 (1996).
The surface hardness of 60 or less was evaluated as ○, and the surface hardness exceeding 60 was evaluated as ×.

− Measurement of foam sheet stiffness −
The flexural modulus of the foamed sheet was measured according to the method of JISK7221-2 (2006).
Evaluation was made with ◯ as the bending elastic modulus of either MD or TD of 50 MPa or more, and X as less than 50 MPa.

Example 2
A polypropylene resin foam sheet was obtained in the same manner as in Example 1 except that the blending amount of the high density polyethylene was 20% by mass. The foamed sheet thus obtained had a surface hardness of 25 and a flexural modulus in the MD direction of 50 MPa.

Comparative Example 1
Extrusion system and resin used were the same as in Example 1, but the die was changed to a 300 mm T-die to obtain a polypropylene resin foam sheet. The foamed sheet thus obtained had a surface hardness of 85 and a flexural modulus in the MD direction of 200 MPa.

Comparative Example 2
A polypropylene resin foam sheet was obtained in the same manner as in Example 1 except that the blending amount of the high density polyethylene was changed to 0% by mass. The obtained foamed sheet had a surface hardness of 72 and a flexural modulus in the MD direction of 130 MPa.

Comparative Example 3
A polypropylene resin foam sheet was obtained in the same manner as in Example 1 except that the blending amount of the high density polyethylene was changed to 30% by mass. The surface hardness of the obtained foamed sheet was 79, and the flexural modulus in the MD direction was 140 MPa.

  These results are summarized in Table 1 below.

As apparent from Table 1 above, in Comparative Example 1, the use of the T-die increased the bulk density to 0.20 g / cm ³ and the surface hardness to 60 or more. Since it does not contain, both loss tangent and bulk density are large, and there is a problem in surface hardness. In Comparative Example 3, the content of ethylene component is as large as 30% by mass, both loss tangent and bulk density are large, and surface hardness and There was a problem with any of the stiffnesses.
On the other hand, it can be seen that Examples 1 and 2 of the present invention are excellent in both surface hardness and rigidity.
As a result, it can be seen that the polyethylene resin foam sheet of the present invention exhibits excellent performance as a partition plate.

1 Extruder 2 Hopper 3 Gas Supply Port 4 Gas Flow Control Device 5 Carbon Dioxide Cylinder 6 Die 7 Foam

Claims (9)

Made of single layer sheet extruded from the porous die, the resin component is a non-crosslinked polypropylene resin also meet any of the following (a) ~ (c), and one of the directions of the sheet in the MD and TD A polypropylene-based resin foam sheet having a flexural modulus of 50 MPa or more .
(A) The amount of ethylene component in the non-crosslinked polypropylene resin is 10 to 20% by mass.
(B) Loss tangent of uncrosslinked polypropylene resin at 190 ° C. and 0.02 rad / s is 0.8 to 2.0.
(C) Bulk density is 0.06 to 0.12 g / cm ³   2. The polypropylene-based resin foam sheet according to claim 1, wherein an average cell diameter is 200 μm or less. Foamed polypropylene resin sheet according to claim 1 or 2, the surface hardness measured by rubber hardness meter spring type C is equal to or Ru der 60 below. The polypropylene resin foam sheet according to any one of claims 1 to 3, wherein the non-crosslinked polypropylene resin is a mixed resin of a homopolypropylene resin and an ethylene resin. A plate material comprising the polypropylene resin foam sheet according to any one of claims 1 to 4 . A method of manufacturing a foamed polypropylene resin sheet comprising a single layer sheet of uncrosslinked polypropylene resin, Ri is 10-20% by mass ethylene component content in the (a) inorganic crosslinked polypropylene resin, (b) inorganic A non-crosslinked polypropylene resin having a loss tangent of 0.8 to 2.0 at 190 ° C. and 0.02 rad / s of the crosslinked polypropylene resin is obtained by an extrusion foaming method using a porous die. a .12g / cm ^3, and a foamed polypropylene resin sheet manufacturing method characterized by the above 50MPa either direction flexural modulus of the sheet in the MD and TD. The method for producing a polypropylene resin foam sheet according to claim 6 , wherein the average cell diameter is 200 μm or less. Foamed polypropylene resin sheet manufacturing method according to claim 6 or 7 spring-type C-type surface hardness measured by rubber hardness meter is equal to or Ru der 60 below. The method for producing a polypropylene resin foam sheet according to any one of claims 6 to 8, wherein the non-crosslinked polypropylene resin is a mixed resin of a homopolypropylene resin and an ethylene resin.

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