Rotational Molding Densification Accelerators Cycle Time

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Solution Overview

Problem

The rotational molding process faces challenges in reducing cycle time and expanding the processing window to achieve optimal mechanical and physical properties of hollow articles, while also minimizing energy costs and rejecting overcooked parts.

Innovation Solution

The use of rotational molding densification accelerators (RMDAs), specifically alkoxylated fatty alcohols, alkoxylated fatty esters, alkoxylated fatty amines, and alkoxylated fatty amides, in the polymer composition to enhance bubble removal and densification, thereby reducing cycle time and broadening the processing window.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the rotational molding process uses conventional polymer compositions without densification accelerators, then the process requires longer cycle times and has a narrow processing window, but adding densification accelerators reduces cycle time and broadens the processing window

Engineering Contradiction:

Improvecycle timeVSAvoidprocessing window

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent changes the chemical composition parameters of the polymer system by introducing densification accelerators (metal salts such as zinc, calcium, or magnesium compounds) that modify the sintering and densification kinetics. This chemical parameter change enables faster bubble removal and denser polymer structure formation, reducing cycle time while maintaining reliable processing across a broader temperature and time window.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If the polymer is exposed to longer times and higher temperatures in the rotational molding process, then complete sintering and bubble removal is achieved, but the polymer degrades leading to discoloration and reduced impact strength

Engineering Contradiction:

Improvebubble removal completenessVSAvoidpolymer degradation

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The densification accelerators act as intermediary substances that facilitate the bubble removal and densification process. These metal salt compounds mediate between the polymer chains and the heating process, enabling efficient energy transfer and rapid sintering at lower temperatures and shorter times, thereby preventing direct excessive thermal exposure that would cause polymer degradation, discoloration, and loss of impact strength.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Loss of energy

If the cycle time is reduced to improve productivity, then energy costs decrease, but the processing window may be narrowed affecting part quality

Engineering Contradiction:

Improveenergy costsVSAvoidpart quality

Core Design Contradiction:

Loss of energyVSManufacturing precision

Solution Approach 1:

By changing the chemical parameters of the polymer composition through the addition of densification accelerators, the patent achieves faster sintering kinetics and more efficient bubble removal. This allows the process to complete within shorter cycle times (reducing energy consumption) while maintaining optimal part quality through controlled densification and proper bubble elimination, thus decoupling the trade-off between cycle time and part quality.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The implementation of RMDAs in the rotational molding process effectively reduces cycle time, lowers energy costs, and expands the processing window, resulting in hollow articles with improved mechanical and physical properties and reduced rejects.

Implementation Method 1

sintering or coalescence brought about by melting the polymer particles to form a continuous phase

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 2

densification of the polymer continuous phase caused by bubble removal

Methodology Applied

Scientific EffectBubble removal:

Implementation Method 3

crystallization of the polymer brought about by cooling

Methodology Applied

Scientific EffectCrystallization: Crystallisation

Data Source

PatentUS20250145792A1Polymer compositions having densification accelerators and rotational molding processes for making hollow articles therefrom

Publication Date: 2025.05.08 CYTEC IND INC

AI summary

Rotational molding processes for producing hollow articles include the steps of: a) filling a mold with a polymer composition comprising: i) an organic polymer; and ii) a rotational molding densification accelerator (RMDA) selected from the group consisting of alkoxylated fatty alcohols, alkoxylated fatty esters, alkoxylated fatty amines, alkoxylated fatty amides, and combinations thereof; b) rotating the mold around at least one axis while heating the mold in an oven, thereby fusing the composition and spreading it to the walls of the mold; c) cooling the mold; and d) opening the mold; and e) removing the hollow article from the mold. The rotational molding processes using such polymer composition results in faster densification, which allows for reduction in overall cycle times for making the hollow articles.