The Catalytic Degradation of Waste PU and the Preparation of Recycled Materials

Abstract

In this paper, we investigated the efficient metal-free phosphorus-nitrogen (PN) catalyst and used the PN catalyst to degrade waste PU with two-component binary mixed alcohols as the alcohol solvent. We examined the effects of reaction temperature, time, and other factors on the hydroxyl value and viscosity of the degradation products; focused on the changing rules of the hydroxyl value, viscosity, and molecular weight of polyols recovered from degradation products with different dosages of the metal-free PN catalyst; and determined the optimal experimental conditions of reaction temperature 180 °C, reaction time 3 h, and PN dosage 0.08%. The optimal experimental conditions were 180 °C, 3 h reaction time, and 0.08% PN dosage, the obtained polyol viscosity was 3716 mPa·s, the hydroxyl value was 409.2 mgKOH/g, and the number average molecular weight was 2616. The FTIR, ¹H, NMR, and other tests showed that the waste urethanes were degraded into oligomers successfully, the recycled polyether polyols were obtained, and a series of recycled polyurethanes with different substitution ratios were then prepared. A series of recycled polyurethane materials with different substitution rates were then prepared and characterized by FTIR, SEM, compression strength, and thermal conductivity tests, which showed that the recycled polyurethane foams had good physical properties such as compression strength and apparent density, and the SEM test at a 20% substitution rate showed that the recycled polyol helped to improve the structure of the blisters.

Keywords: PN catalyst; alcoholysis; recycled materials; waste polyurethane.

Figure 2

The hydroxyl value and viscosity of recovered polyols at different reaction times.

Figure 1

Degradation process flow diagram for polyurethane degradation with PN catalysts.

Figure 3

The hydroxyl value and viscosity of recovered polyols at different reaction temperatures.

Figure 4

Hydroxyl value and viscosity of recycled polyols at different catalyst additions.

Figure 5

GPC curve of polyether 4110 and recovered polyols at different catalyst dosages.

Figure 6

Infrared spectrum of WPUF.

Figure 7

Infrared spectra of RP and polyether 4110.

Figure 8

¹H NMR spectra of recovered polyols and commercial polyether polyols.

Figure 9

Schematic diagram of the mechanism of the catalytic degradation of waste polyurethane by PN catalysts.

Figure 10

Infrared spectra of RPU with different recovery polyol substitution rates.

Figure 11

Compressive strength and apparent density of RPU at different recycled polyol substitution rates.

Figure 12

Thermal conductivity of RPU at different substitution rates.

Figure 13

SEM images of RPU prepared with different recycled polyols at a substitution rate of 20%. Types of polyols used: (a) Polyether 4110 (b) RP-0.02 (c) RP-0.04 (d) RP-0.06 (e) RP-0.08 (f) RP-0.10.

Figure 14

The relationship between the amount of PN catalyst and the size of the pore diameter.

Figure 15

SEM images of recycled polyurethane prepared by recycled polyol RP4 with different substitution rates: (a)RPU-0; (b) RPU-10; (c) RPU-20; (d) RPU-30; (e) RPU-40.

Figure 16

Relationship between different substitution rates and the pore size of recovered polyols.

Figure 17

Heat loss curve of recycled polyurethane.