Polypropylene Resin Composition for Uniform Foamed Sheet Cells

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Solution Overview

Problem

Conventional polypropylene-based resin compositions with long chain branches face issues such as poor moldability, uneven structure formation in shear flow, and limited melt tension, leading to suboptimal foamed sheet quality and appearance in extrusion foaming processes.

Innovation Solution

A polypropylene-based resin composition combining a polypropylene resin with long chain branches and a specific propylene-ethylene block copolymer, optimized through sequential polymerization, to prevent shear-induced crystalline structure formation, enhancing melt tension, moldability, and extensibility, resulting in a foamed sheet with fine and uniform cells.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If long chain branches are introduced into polypropylene by high-energy ionization radiation or organic peroxide to increase melt tension, then melt tension is improved, but production cost increases and yellowing occurs

Engineering Contradiction:

Improvemelt tensionVSAvoidproduction cost

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The patent changes the molecular weight distribution parameters of polypropylene by blending resins with different molecular weights and architectures (linear vs. branched). This achieves high melt tension through parameter optimization rather than expensive chemical modification, resolving the contradiction between improved strength and manufacturing ease.

Inventive Principle:

Principle #35Parameter changes

2Strength

If long chain branches are introduced into polypropylene by high-energy ionization radiation or organic peroxide to increase melt tension, then melt tension is improved, but yellowing and change in physical properties over time occur

Engineering Contradiction:

Improvemelt tensionVSAvoidstability of physical properties

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

Instead of using expensive and unstable chemically-modified polypropylene with long chain branches, the patent employs conventional polypropylene resins with appropriate molecular weight distributions. This achieves comparable melt tension through physical blending rather than chemical modification, improving reliability by avoiding yellowing and property degradation over time.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Ease of manufacture

If conventional polypropylene with low melt tension is used, then production cost is reduced, but foaming properties and expandability deteriorate

Engineering Contradiction:

Improveproduction costVSAvoidfoaming properties

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The patent creates a composite resin composition by blending polypropylene resins with different molecular weight characteristics. This composite structure combines the low-cost advantage of conventional polypropylene with the high expandability of high-melt-tension resins, achieving both cost reduction and improved foaming properties simultaneously.

Inventive Principle:

Principle #40Composite materials

4Strength

If polypropylene with broadened molecular weight distribution is used to increase melt tension, then melt tension is improved, but moldability deteriorates

Engineering Contradiction:

Improvemelt tensionVSAvoidmoldability

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The patent applies local quality by using a multi-component resin system where each component has specific molecular weight characteristics. The blend contains resins with narrow molecular weight distribution for good moldability and resins with broader distribution for high melt tension, achieving both properties in different phases of the molding process through localized functional contribution.

Inventive Principle:

Principle #3Local quality

Data Source

PatentEP2818511B1Polypropylene-based resin composition and foam sheet

Publication Date: 2015.10.21 JAPAN POLYPROPYLENE CORP

Figure 1(a)~1(b)
Figure 2
Figure 3~4

AI summary

Provided is a polypropylene-based resin composition which gives uniform and fine cells and from which a foamed sheet and thermoform excellent in appearance, thermoformability, impact resistance, lightness, stiffness, heat resistance, heat insulating properties, oil resistance and the like can be produced. A polypropylene-based resin composition comprising (X) 5 to 99 % by weight of a polypropylene resin having a structure with long chain branches, and (Y) 1 to 95 % by weight of a propylene-based block copolymer produced by sequential polymerization, which block copolymer comprises (Y-1) a propylene (co) polymer and (Y-2) a propylene-ethylene copolymer, said resin (X) having properties (X-i) to (X-iv) and said block copolymer (Y) having properties (Y-i) to (Y-v), and the like.