Experimental Study on Preparation of Foamed Packaging Cushioning Material from Waste Paper

[Abstract]: The manufacturing process of foamed packaging cushioning material using waste paper as raw material and starch as binder was studied. The gelatinization temperature of the starch was 65[deg.] C. and the gelatinization time was 30 min. Na2CO3 was added as a pasting agent and a subsequent foaming agent. After the waste paper was mixed with the starch paste, citric acid and borax were added, respectively, as a reagent for Na2CO3 and a cross-linker for starch. The mass ratio (for starch) of various materials was: Waste paper: Starch: Sodium carbonate: Citric acid: Borax: Water 2.3:1.0:0.32:0.45:0.1:10.0. The suitable process conditions for foaming are: the ratio of 1:2 paper dust paper mass, the foaming temperature 130°C, and the foaming time 7 h. The apparent density of the resulting packaging cushioning material is about 0.2 g/cm3 and the compressive strength is greater than 700 KPa.

In recent years, some countries have successively made decisions to restrict or prohibit the use of foamed plastics as packaging cushioning materials, so that pulp molded products are favored. Compared with foamed plastic, pulp molded products solve the problem of white pollution, but the weight, structural strength and cushioning properties are less than 1/10 of materials such as EPS, high energy consumption in the production process, and drainage pollution. Pulp molded products must also be improved. The dry pulp molded products that emerged in the 1990s have overcome the above shortcomings. This study tried to adopt waste paper and starch as basic raw materials and use chemical methods for foaming to make a new type of light environmental protection buffer packaging material in order to overcome the above shortcomings of pulp molded products to a greater extent.

1, experiment

1.1 experimental materials

1) Waste paper. The waste newspapers are chopped by a chopper to make two sizes, one is fluffy paper and the other is shredded paper. Separately place the balance water in a plastic bag.

2) Starch. Potato starch (primary product) with good binding and filming properties was selected and prepared into starch paste according to a certain formula.

1.2 Experimental Methods and Equipment

The waste paper was disintegrated into paper and paper using a TQ-1 multi-purpose chopper, then moistened with a small amount of water, and mixed with the mash. The citric acid is added to the waste paper starch mixture, and the borax is added after mixing well. The final mixture is injection molded and placed in a drying oven for heating and foaming. After a certain period of foaming, the semi-dried foamed body is taken out to dry. , that is made into foamed moldings.

1.3 Physical Detection

1) Density testing. The foamed product was wrapped with a plastic film by vacuum sizing, and then its volume was measured by a drainage method, and the density was determined based on its quality.

2) Compression strength test: According to GB8813-88 (ISO 844-1978) related to the rigid foam compression test method, the use of ZYD-2 electronic compression tester.

2. Results and Discussion

2.1 Paste and Foam of Starch

The experiment uses starch as a binder to bind paper and paper scraps, and to reduce the density of the product by foaming to improve the buffering performance. First starch paste to make a starch paste. In order to ensure good mixing with the paper and the paper, the starch paste needs a certain degree of fluidity, and at the same time, in order to prevent the foaming gas from escaping excessively, the starch binder used must have good film forming properties. Due to the ease of gelatinization of potato starch, adhesion and film formation are superior to corn starch. Therefore, potato starch was selected as the raw material for the adhesive.

In order to promote the gelatinization of starch, it is generally necessary to add a base as a gelatinizer so that the starch swells and breaks some of the internal hydrogen bonds of the starch, weakening the interaction between macromolecules and lowering the gelatinization temperature. In this experiment, sodium carbonate was used as a gelatinizer, and sodium carbonate was also used as a foaming agent for waste paper starch packaging materials. When sodium carbonate reacts with acid, carbon dioxide gas can escape. The acid used in this experiment was citric acid. The foaming reaction mechanism is as follows:

2HOC3H24(COOH) 3+3Na2CO3→2HOC3H4(COO Na) 3+3H2O+3CO2 ↑

In order to increase the initial viscosity of the gelatinized starch and make the formed film have a higher strength to better block the carbon dioxide gas generated by the reaction of sodium carbonate and acid, borax is used as a cross-linking agent. After hydrolysis of borax, cross-linking reaction occurs with the reactive groups in the fully swollen starch to increase intermolecular cohesion.

The formulation and gelatinization process conditions of the starch gelatinization and foaming auxiliary agents finally determined in this study were as follows: starch: sodium carbonate: citric acid: borax: the mass ratio of water was 1:0.32:0.45:0.1:10.0. Pasting temperature 65 °C, gelatinization time 30min. (to be continued)