JP2006249350A - Resin composition for foam molding and foamed molded article formed from the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a foamed molded article that is excellent in heat resistance, heat insulation properties, cushioning properties and surface appearance. <P>SOLUTION: A resin composition for foam molding comprises (A) 60-99 wt% propylene polymer having a melt flow rate (MFR, ASTM D1238, 230°C, a load of 2.16 kg) of 0.1-50 (g/10 min) and a melting point of 120-170°C as measured by a differential scanning calorimeter (DSC), (B) 1-40 wt% propylene/α-olefin random copolymer having a melt flow rate (MFR, ASTM D1238, 190°C, a load of 2.16 kg) of 0.1-50 (g/10 min) and a melting point of 100°C or less as determined by differential scanning calorimetry (DSC), and (C) 0.5-100 pts.wt. foaming agent based on 100 pts.wt. of the composition comprising the components (A) and (B). The foamed molded article formed from the composition is suitable for use as a molded article such as a packing container for food and medical products, a sheet for shipping and building materials, and the like. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a resin composition for foam molding and a foam molded article obtained therefrom.

  Polypropylene is a material with excellent heat resistance, chemical resistance and hygiene compatibility, and its molded products have excellent rigidity and impact resistance, and are used in food containers, detergent containers, medical containers, various trays, etc. . Foam molded products obtained from polypropylene are further excellent in light weight, buffer properties, heat insulation, etc., and are used in food containers and logistics materials. However, when the bubble cells in these foamed molded products are coarse or non-uniform, the foamed molded products have insufficient strength and the surface appearance of the molded products is inferior. Accordingly, there has been a demand for a resin composition in which the foamed foam is finer and a uniform foamed molded product can be obtained.

Japanese Patent Application Laid-Open No. 11-228629 discloses a foam molded product obtained from a specific propylene polymer. Even in the method according to this publication, the molding conditions are limited in order to obtain fine and uniform bubble cells. (Patent Document 1)
JP 11-228629 A

   An object of the present invention is to provide a resin composition for foam molding, which can obtain a foam molded article having fine and uniform cell cells, excellent strength and surface appearance, and a foam molded article obtained from the composition.

Propylene system having a melt flow rate (MFR, ASTM D1238, 230 ° C., 2.16 kg load) of 0.1 to 50 (g / 10 min) and a melting point of 120 to 170 ° C. measured by a differential scanning calorimeter (DSC) 60 to 99% by weight of polymer (A),
A melt flow rate (MFR, ASTM D1238, 190 ° C., 2.16 kg load) of 0.1 to 50 (g / 10 min) and a melting point determined by differential scanning calorimetry (DSC) is 100 ° C. or less. α-olefin random copolymer (B) 1 to 40% by weight,
The present invention relates to a foam molding resin composition comprising 0.5 to 100 parts by weight of a foaming agent (C) with respect to 100 parts by weight of the composition comprising (A) and (B).

  Furthermore, this invention relates to the foaming molding which consists of a resin composition of the said invention.

  The foam molded article obtained from the resin composition of the present invention has good heat resistance, heat insulation, buffering properties, strength, surface appearance, and packaging containers for food and medicine, logistics, construction materials, sheets for automobile materials, etc. It can be suitably used as a molded product.

Propylene polymer (A)
Examples of the propylene polymer (A) in the resin composition of the present invention include a known propylene homopolymer, or a random or block copolymer with ethylene or an α-olefin having 4 to 20 carbon atoms. The melt flow rate (MFR, ASTM D1238, 230 ° C., 2.16 kg load) of the propylene-based polymer is 0.1 to 50 (g / 10 minutes), preferably 0.2 to 40 (g / 10 minutes), A propylene polymer having a melting point measured by a differential scanning calorimeter (DSC) in the range of 120 to 170 ° C., preferably 125 to 165 ° C. is preferably used. By using such a propylene polymer, a foamed molded article having excellent heat resistance can be obtained. The propylene content of the propylene polymer (A) is 80 to 100 mol%, preferably 85 to 100 mol%.

  Such a propylene-based polymer (A) typically contains propylene in the presence of a solid titanium catalyst and a catalyst mainly composed of an organometallic compound or a metallocene catalyst using a metallocene compound as one component of the catalyst. It can be produced by polymerization or copolymerization of propylene and other α-olefins.

Propylene / α-olefin random copolymer (B)
The propylene / α-olefin random copolymer (B) used in the present invention has a melting point measured by DSC method (after holding at 200 ° C. for 5 minutes, the temperature is lowered to −20 ° C. at a rate of temperature fall of −20 ° C./min. Thereafter, an endothermic peak when observed when the temperature is increased again to 180 ° C. at 20 ° C./min) is 100 ° C. or less, preferably in the range of 40 to 95 ° C., more preferably in the range of 50 to 90 ° C.

  The propylene / α-olefin random copolymer (B) can be obtained by copolymerizing propylene and another α-olefin using a known stereoregular catalyst, and is particularly copolymerized using a metallocene catalyst. It is desirable that the molded product has less stickiness of the molded body. In this case, the molecular weight distribution obtained from gel permeation chromatography (GPC) is in the range of 1-3.

  The α-olefin copolymerized with propylene is at least one α-olefin having 2 to 20 carbon atoms (excluding propylene) including ethylene, 1-butene and 1-pentene, preferably 1-butene or 1-butene is the main component. The α-olefin content of the propylene / α-olefin random copolymer (B) is 5 to 50 mol%, preferably 10 to 35 mol%.

Such a propylene copolymer can be obtained, for example, using a catalyst as described in International Publication No. WO95 / 14717. Such a propylene copolymer has a comonomer constituent unit content M (mol%) determined by measurement of the melting point Tm (° C.) and 13 C-NMR spectrum of 146 exp (−0.022 M) ≧ Tm ≧ 125 exp (−0. 032M)
Those within the range are desirably used.
The melt flow rate (hereinafter abbreviated as MFR (230 ° C.)) measured under a load of 2.16 kg at 230 ° C. based on ASTM D-1238 of the propylene / α-olefin random copolymer (B) is 0. It is in the range of 1-50 (g / 10 minutes), preferably 1-20 (g / 10 minutes).

Foaming agent (C)
The foaming agent (C) in the resin composition of the present invention is appropriately selected from chemical foaming agents and gas foaming agents based on the molding method and molding temperature of the foamed molded product of the present invention.

  Chemical foaming agents include azo compounds such as azodicarboxylic acid amide and azobisisobutyronitrile, hydrazide compounds such as benzosulfonyl hydrazide, toluenesulfonyl hydrazide, p, p'-oxybis (benzenesulfonyl hydrazide), and dinitrosopentamethylene. Examples thereof include nitroso compounds such as tetramine, alkali metal hydrogen carbonates such as sodium hydrogen carbonate and sodium carbonate, alkali metal carbonates or a mixture thereof, etc., which decompose themselves under molding conditions for foam molding. It generates gas. Moreover, you may use a foaming adjuvant with these foaming agents as needed. Examples of the foaming aid include organic acids such as zinc oxide, zinc stearate, calcium stearate, salicylic acid, phthalic acid, oxalic acid and citric acid.

  Examples of gas blowing agents include carbon dioxide, halogenated hydrocarbons such as difluorodichloromethane, hydrocarbons such as butane, pentane, hexane, cyclobutane, and cyclohexane, which are themselves gases under molding conditions. Contributes to foam molding. One type of foaming agent may be used, or a plurality of types may be used in combination.

Resin Composition The resin composition of the present invention comprises a propylene-based polymer (A), a propylene / α-olefin random copolymer (B), and a foaming agent (C). ˜99, preferably 70 to 98% by weight, (B) 1 to 40, preferably 2 to 30% by weight, and (C) 0.5 to 100 parts by weight of the composition comprising (A) and (B). -100 parts by weight, preferably 1-50% by weight. When the ratio of each component is within this range, the foamed molded product obtained from the composition is excellent in heat resistance, strength and surface appearance, and a practically suitable molded product can be obtained.

  A characteristic of the resin composition of the present invention is that a propylene / α-olefin random copolymer having a specific property is used as a component of the resin composition. By using the propylene / α-olefin random copolymer as described above, the foamed cells are fine and uniform under a wide range of molding conditions, and as a result, the molded product has excellent strength and surface appearance.

   In the present invention, as long as the performance as the foam molding resin composition of the present invention is not impaired, other synthetic resins and rubbers, or antioxidants, heat stabilizers, weather stabilizers, slip agents, It may contain an antiblocking agent, a crystal nucleating agent, a pigment, a hydrochloric acid absorbent additive or an inorganic filler.

    Further, after blending the above components and various additives as necessary, for example, with a mixer such as a Henschel mixer, a Banbury mixer, a tumbler mixer, etc., blow molding described later as a pellet using a uniaxial or biaxial extruder However, it can also be used in a known molding machine such as a sheet molding machine or an injection molding machine in a state where the components are blended.

Foam molded article A foam molded article can be produced by foam molding from the resin composition of the present invention. As the foam molding method, any conventionally known molding method employed for polyolefins such as polypropylene can be used without limitation. Specifically, it is possible to employ injection molding as well as single-layer sheets and multilayer sheets by calendar molding and T-die molding.

  There are no particular restrictions on the foaming conditions, but a method may be employed in which a non-foamed molded article is once molded from a resin composition to which a foaming agent has been added in advance, and then the temperature is raised to change to a foamed molded article. The method of obtaining a foaming molding directly from the resin composition which added the agent may be sufficient.

  The expansion ratio of the foamed molded product of the present invention is 0.5 to 20 times, preferably 0.5 to 18 times, and more preferably 1 to 10 times.

The foamed molded product of the present invention may be a foamed or unfoamed molded product made of another resin or a laminate with a metal, and the foamed molded product of the present invention only needs to be used in at least one layer. Examples of other resins when used as a laminate include molded products obtained from polypropylene, polyethylene, polyamide, and polyester, and foams thereof. In the case of taking such a composite laminated structure, a known coextrusion method, dry lamination method or extrusion lamination method can be preferably used. However, the present invention is not limited thereto. When the molded body is used as a container for foods, medical products, etc., it can be laminated with an ethylene-vinyl alcohol copolymer, polyamide or the like having an excellent barrier property against oxygen or the like for the purpose of protecting the contents. At this time, if a modified polyolefin such as an unsaturated carboxylic acid grafted polyolefin is used as the adhesive resin, the adjacent layers can be firmly bonded.

EXAMPLES Next, although an Example demonstrates this invention, this invention is not limited to this.
[Example 1]
(Manufacture of foam moldings)
A T-die molding machine having a width of 300 mm and a single screw extruder having a screw diameter of 40 mmφ, 90% by weight of propylene polymer (melting point 161 ° C., MFR (230 ° C.) 2.0 g / 10 min, homopolypropylene), propylene 1-butene copolymer (MFR (230 ° C.) 7.0 g / 10 min, 1-butene content 26 mol%, melting point 75 ° C.) 10 wt%, propylene-based polymer and propylene / 1-butene copolymer A resin composition in which 2.5 parts by weight of sodium bicarbonate and 2.5 parts by weight of citric acid were added as a foaming agent to 100 parts by weight of the composition was introduced. By foam molding at a resin temperature of 210 ° C., a foam sheet having a thickness of 1 mm was obtained. Table 1 shows the physical properties of the obtained sheet.

Foaming ratio: Measure the specific gravity of the foam with a submersible densitometer, and the resin composition used as the raw material
Calculated from density.

Surface appearance: The surface of the foam sheet is visually observed, and the surface is smooth.
The case where somewhat rough was seen was marked with △, and the case where markedly rough was marked with x.
[Comparative Example 1]
The foamed molded product was evaluated in the same manner as in Example 1 except that the resin composition described in Table 1 was used. The results are shown in Table 1.
[Example 2]
The foamed molded product was evaluated in the same manner as in Example 1 except that the resin composition described in Table 1 was used. The results are shown in Table 1.

  As is clear from the results shown in Table 1, a foam excellent in surface appearance can be obtained by using the foam molding resin composition of the present invention.

In the foam molding resin composition of the present invention, the molded product obtained therefrom is excellent in heat resistance, heat retention, buffering and surface appearance, and is a molded product for food, medical containers, logistics, building materials sheets, and automotive materials. Etc. can be suitably used.

Claims (3)

Propylene system having a melt flow rate (MFR, ASTM D1238, 230 ° C., 2.16 kg load) of 0.1 to 50 (g / 10 min) and a melting point of 120 to 170 ° C. measured by a differential scanning calorimeter (DSC) 60 to 99% by weight of polymer (A),
A melt flow rate (MFR, ASTM D1238, 190 ° C., 2.16 kg load) of 0.1 to 50 (g / 10 min) and a melting point determined by differential scanning calorimetry (DSC) is 100 ° C. or less. α-olefin random copolymer (B) 1 to 40% by weight,
A resin composition for foam molding comprising 0.5 to 100 parts by weight of a foaming agent (C) with respect to 100 parts by weight of the composition comprising (A) and (B).   The resin composition for foam molding according to claim 1, wherein the propylene / α-olefin random copolymer (B) according to claim 1 is a propylene / α-olefin random copolymer obtained by a metallocene catalyst.    A foam-molded product comprising the foam-molded resin composition according to claim 1 or 2 as at least one layer, and the foam-molded resin composition layer is foamed 0.5 to 20 times.